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Title: Structural And Optical Properties Of Nanocrystalline Tio2 With Multiwalled Carbon Nanotubes And Its Photovoltaic Studies Using Ru(ii) Sensitizers.
Creator: Delekar, Sagar D., Dhodamani, Ananta G., More, Krantiveer V., Dongale, Tukaram D., Kamat, Rajanish K., Acquah, Steve F. A., Dalal, Naresh S., Panda, Dillip K.
Abstract/Description: In this study, the in situ sol-gel method has been deployed to prepare the titanium dioxide/multiwalled carbon nanotubes (TiO2/MWCNTs) nanocomposite (NCs) powders with varying content of MWCNTs (0.01-1.0 wt %), to construct the dye-sensitized solar cells (DSSCs). First, binder-free NCs were deposited on a transparent-conducting F:SnO2 (FTO) glass substrate by a doctor-blade technique and then anchored with Ru(II)-based dyes to either N719 or ruthenium phthalocyanine (RuPc). The structural and...
Show moreIn this study, the in situ sol-gel method has been deployed to prepare the titanium dioxide/multiwalled carbon nanotubes (TiO2/MWCNTs) nanocomposite (NCs) powders with varying content of MWCNTs (0.01-1.0 wt %), to construct the dye-sensitized solar cells (DSSCs). First, binder-free NCs were deposited on a transparent-conducting F:SnO2 (FTO) glass substrate by a doctor-blade technique and then anchored with Ru(II)-based dyes to either N719 or ruthenium phthalocyanine (RuPc). The structural and optical properties and interconnectivity of the materials within the composite are investigated thoroughly by various spectral techniques (XRD, XPS, Raman, FT-IR, and UV-vis), electron microscopy (HRTEM), and BET analysis. The experimental results suggest that the ratio of MWCNTs and TiO2 in NCs, morphology, and their interconnectivity influenced their structural, optical, and photovoltaic properties significantly. Finally, the photovoltaic performances of the assembled DSSCs with different content of MWCNTs to TiO2 films anchored with two different dyes were tested under one sun irradiation (100 mW/cm(2)). The measured current-voltage (IV) curve and incident photon-to-current conversion efficiency (IPCE) spectra of TiO2/0.1 wt % MWCNTs (T@0.1 C) for N719 dye show three times more power conversion efficiency (eta = 6.21%) which is opposed to an efficiency (eta = 2.07%) of T@0.1 C for RuPc dye under the same operating conditions.
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Date Issued: 2018-03
Identifier: FSU_libsubv1_wos_000427939400031, 10.1021/acsomega.7b01316
Format: Citation

Title: Cell Adhesion and Proliferation on the “Living” Surface of a Polyelectrolyte Multilayer.
Creator: Arias, Carlos B., Surmaitis, Richard L., Schlenoff, Joseph B.
Abstract/Description: The adhesion of living eukaryotic cells to a substrate, one of the most complex problems in surface science, requires adsorption of extracellular proteins such as fibronectin. Thin films of polyelectrolyte complex made layer-by-layer (polyelectrolyte multilayers or PEMUs) offer a high degree of control of surface charge and composition - interconnected and essential variables for protein adhesion. Fibroblasts grown on multilayers of poly(styrene sulfonate), PSS, and poly...
Show moreThe adhesion of living eukaryotic cells to a substrate, one of the most complex problems in surface science, requires adsorption of extracellular proteins such as fibronectin. Thin films of polyelectrolyte complex made layer-by-layer (polyelectrolyte multilayers or PEMUs) offer a high degree of control of surface charge and composition - interconnected and essential variables for protein adhesion. Fibroblasts grown on multilayers of poly(styrene sulfonate), PSS, and poly(diallyldimethylammonium), PDADMA, with increasing thickness exhibit good adhesion until the 12th layer of polyelectrolyte has been added, whereupon there is a sudden transition to nonadhesive behavior. This sharp change is due to the migration of excess positive charge to the surface – a previously unrecognized property of PEMUs. Precise radiotracer assays of adsorbed 125I-albumin, show how protein adsorption is related to multilayer surface charge. With more negative surface charge density from the sulfonates of PSS, more albumin adsorbs to the surface. However, a loosely-held or “soft corona” exchanges with serum protein under the Vroman effect, which is correlated with poor cell adhesion. A comprehensive view of cell adhesion highlights the central role of robust protein adhesion, which is required before any secondary effects of matrix stiffness on cell fate can come into play.
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Date Issued: 2016-05-18
Identifier: FSU_libsubv1_scholarship_submission_1540238895_2ac07ed1, 10.1021/acs.langmuir.6b00784
Format: Citation

Title: Modular Access To Functionalized 5-8-5 Fused Ring Systems Via A Photoinduced Cycloisomerization Reaction.
Creator: Salvati, Anna E., Law, James A., Liriano, Josue, Frederich, James H.
Abstract/Description: A 5-8-5 carbocyclic ring system forms the core of over 30 distinct natural products. Several members of this family have gained attention for their diverse activity in cell culture. In these cases, biological function is mediated by the arrangement of substituents around a conserved 5-8-5 nucleus. Despite the potential applications of this privileged substructure in medicinal chemistry, modular strategies for its assembly are underdeveloped. Herein, we describe a cycloisomerization reaction...
Show moreA 5-8-5 carbocyclic ring system forms the core of over 30 distinct natural products. Several members of this family have gained attention for their diverse activity in cell culture. In these cases, biological function is mediated by the arrangement of substituents around a conserved 5-8-5 nucleus. Despite the potential applications of this privileged substructure in medicinal chemistry, modular strategies for its assembly are underdeveloped. Herein, we describe a cycloisomerization reaction that forms the 5-8-5 framework directly. This strategy uniquely allows access to gram quantities of this valuable scaffold in four steps.
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Date Issued: 2018-06-28
Identifier: FSU_libsubv1_wos_000436027800011, 10.1039/c8sc00999f
Format: Citation

Title: Static and Dynamic Solution Behavior of a Polyzwitterion Using a Hofmeister Salt Series.
Creator: Delgado, Jose D., Schlenoff, Joseph
Abstract/Description: Polymers made from zwitterionic repeat units (bearing no net charge) have intriguing solution properties, especially in contrast to polyelectrolytes, such as an apparent indifference to salt concentration. These polyzwitterions, PZs, have come under renewed scrutiny because of their use in high performance antifouling coatings. Here, an amidosulfobetaine polymer was used to shed light on the complex and poorly-understood response of PZ solution conformation to ionic strength. A Hofmeister...
Show morePolymers made from zwitterionic repeat units (bearing no net charge) have intriguing solution properties, especially in contrast to polyelectrolytes, such as an apparent indifference to salt concentration. These polyzwitterions, PZs, have come under renewed scrutiny because of their use in high performance antifouling coatings. Here, an amidosulfobetaine polymer was used to shed light on the complex and poorly-understood response of PZ solution conformation to ionic strength. A Hofmeister anion series NaX, where X = SO4 2, Cl-, Br-, NO3-, ClO4- and SCN provided a systematic way to tune PZ/ion interactions. A consistent picture of PZ conformation emerged, where the role and location of counterions (how they pair with the polymer chain) depends on their position in the Hofmeister series. At least four regimes of PZ conformation/interaction as a function of ionic strength were observed, the last showing no change in coil size (hydrodynamic radius) as a function of ionic strength for all salts in the concentration range 0.6 M – 4 M. Hydrophobic (less hydrated) anions ClO4- and SCN yielded a clear minimum in coil size at lower [NaX] whereas PZ in solutions of hydrophilic ions SO4- and Cl showed only a hint of the much-discussed “antipolyelectrolyte” expansion of PZ with increasing [NaX]. Static light scattering results, when analyzed using Stockmeyer’s theory of scattering from multicomponent systems, revealed that NaX is associated with PZ with a corresponding increase in apparent molecular weight. Light scattering measurements at low [NaX] show solution ions are excluded from PZ coils dressed with hydrophobic NaX. DLS in salt-free solutions at elevated temperatures revealed substantial chain stiffening of PZ, thought to be caused by nearest-neighbor interactions between zwitterion groups. DLS yielded a fast mode in these salt free solutions, ascribed to soliton-like transport of waves of associated zwitterionic groups along the PZ backbone.
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Date Issued: 2017-05-25
Identifier: FSU_libsubv1_scholarship_submission_1540240683_30337f56, 10.1021/acs.macromol.7b00525
Format: Citation

Title: Water and the Glass Transition Temperature in a Polyelectrolyte Complex.
Creator: Fu, Jingcheng, Abbett, Rachel L., Fares, Hadi M., Schlenoff, Joseph B.
Abstract/Description: Hydrated polyelectrolyte complexes, H-PECs, have recently started attracting renewed interest as a class of highly solvated/plasticized blends. H-PECs are observed to undergo a transition in mechanical properties close to room temperature. Whether this is a true glass transition has been questioned recently: the material has an unusually low modulus in the “glassy” state and molecular dynamics simulations have suggested temperature-induced dehydration and water structure changes are...
Show moreHydrated polyelectrolyte complexes, H-PECs, have recently started attracting renewed interest as a class of highly solvated/plasticized blends. H-PECs are observed to undergo a transition in mechanical properties close to room temperature. Whether this is a true glass transition has been questioned recently: the material has an unusually low modulus in the “glassy” state and molecular dynamics simulations have suggested temperature-induced dehydration and water structure changes are responsible for the transition. Using in situ infrared spectroscopic methods on thin films of a widely-studied H-PEC we find no definitive evidence for changes in the hydration state of functional groups, the water content, or water structure below or above Tg for stoichiometric and nonstoichiometric H-PECs. These complexes represent a promising platform for fundamental studies of the glass transition, since the coupling between chains can be modified by “doping” the material with salt, which breaks ion pairing crosslinks. The Fox equation was used to estimate Tg’s for paired and unpaired oppositely-charged repeat units.
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Date Issued: 2017-09-22
Identifier: FSU_libsubv1_scholarship_submission_1540241093_22e4df52, 10.1021/acsmacrolett.7b00668
Format: Citation

Title: Towards Ion-Free Polyelectrolyte Multilayers: Cyclic Salt Annealing.
Creator: Fares, Hadi M., Ghoussoub, Yara E., Surmaitis, Richard L., Schlenoff, Joseph B.
Abstract/Description: Polyelectrolyte multilayers (PEMUs) are made from various combinations of polyanions and polycations. It is now understood that these ultrathin films of polyelectrolyte complex may also incorporate counterions derived from the solution from which the PEMU was deposited, or exchanged into the film post-assembly. If these ions are required to compensate nonstoichiometric ratios of polycation and polyanion they cannot leave the film and they exert considerable influence on film properties, such...
Show morePolyelectrolyte multilayers (PEMUs) are made from various combinations of polyanions and polycations. It is now understood that these ultrathin films of polyelectrolyte complex may also incorporate counterions derived from the solution from which the PEMU was deposited, or exchanged into the film post-assembly. If these ions are required to compensate nonstoichiometric ratios of polycation and polyanion they cannot leave the film and they exert considerable influence on film properties, such as modulus and permeability. These “extrinsic” charges also complicate fundamental studies on PEMUs. We report a method to remove almost all ionic content from a PEMU made of poly(diallyldimethylammonium chloride), PDADMAC, and poly(styrene sulfonate), PSS. In this method, a high salt concentration plasticizes the multilayer past its glass transition, dispersing all the buried excess PDADMA throughout the film. Exposure to a solution of PSS in a lower salt concentration consumes excess PDADMA near the surface without overcompensating with PSS. The process is repeated in a cyclic fashion, removing >95% of the ions charge present in the as-made PEMU.
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Date Issued: 2015-02-22
Identifier: FSU_libsubv1_scholarship_submission_1540241506_9d2111db, 10.1021/la504910y
Format: Citation

Title: Ion-Pairing Strength in Polyelectrolyte Complexes.
Creator: Fu, Jingcheng, Fares, Hadi M., Schlenoff, Joseph
Abstract/Description: Polyelectrolyte complexes, PECs, are spontaneously formed blends of polyelectrolytes bearing positive, Pol+, and negative, Pol-, repeat units. Many interesting PEC morphologies have been observed, ranging from dense precipitates to liquid-like coacervates to quasi-stable nanoparticles, depending on the identity of the polymers and the preparation conditions. While the number of polyelectrolytes available to synthesize these materials is large and increasing, the corresponding number of Pol+...
Show morePolyelectrolyte complexes, PECs, are spontaneously formed blends of polyelectrolytes bearing positive, Pol+, and negative, Pol-, repeat units. Many interesting PEC morphologies have been observed, ranging from dense precipitates to liquid-like coacervates to quasi-stable nanoparticles, depending on the identity of the polymers and the preparation conditions. While the number of polyelectrolytes available to synthesize these materials is large and increasing, the corresponding number of Pol+/Pol- combinations is vast. This work quantitatively compares the binding strengths between a selection of positive and negative polyelectrolytes by evaluating the extent to which ion pairs between them are broken by a common salt, KBr. Comparison of association constants or Gibbs free energies between different classes of ionic functionality reveals that more “hydrophilic” PECs are more weakly associated, small primary amines bind strongly, carboxylates bind weakly, and aromatic sulfonates interact more strongly than aliphatic ones. The use of “charge density” to predict binding strength is shown not to be justified. Ion diffusion coefficients through PECs also approximately follow water content and are inversely related to interaction strength.
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Date Issued: 2017-01-26
Identifier: FSU_libsubv1_scholarship_submission_1540239998_385e9eae, 10.1021/acs.macromol.6b02445
Format: Citation

Title: Equilibrium Overcompensation in Polyelectrolyte Complexes.
Creator: Fares, Hadi M., Schlenoff, Joseph
Abstract/Description: Association between positive, Pol+, and negative, Pol-, units on polyelectrolytes drive spontaneous formation of a range of morphologies, some with “fuzzy” structure but most essentially amorphous. An excess of one type of charge over the other, known as overcompensation or overcharging, is essential for certain types of processing, such as the formation of polyelectrolyte “multilayers” on substrates or “polyplex” nanoparticles in solution. In this work, uniform, stoichiometric, smooth thin...
Show moreAssociation between positive, Pol+, and negative, Pol-, units on polyelectrolytes drive spontaneous formation of a range of morphologies, some with “fuzzy” structure but most essentially amorphous. An excess of one type of charge over the other, known as overcompensation or overcharging, is essential for certain types of processing, such as the formation of polyelectrolyte “multilayers” on substrates or “polyplex” nanoparticles in solution. In this work, uniform, stoichiometric, smooth thin films of polyelectrolyte complex, PEC, from poly(diallyldimethylammonium), PDADMA, and poly(styrene sulfonate), PSS, were prepared starting from rough, nonstoichiometric multilayers of these materials. A narrow concentration range of added salt was found which promoted steady-state bulk overcompensation of PEC films in the presence of a large excess of polycation or polyanion without loss of PEC to solution. The extent of overcompensation, about 35% for PDADMA in 1.0 M NaCl and about 40% for PSS in 1.4 M NaCl, was independent of solution polymer concentration and only weakly dependent on salt concentration. A weak dependence of overcompensation on molecular weight was also determined. Erosion/instability of films for [NaCl] > 1.4 M was observed, with more prominent or faster erosion for higher molecular weight PSS. The mechanism for overcompensation in this entropically driven system was attributed to the formation of a Donnan ion equilibrium between the PEC and solution phases.
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Date Issued: 2017-05-09
Identifier: FSU_libsubv1_scholarship_submission_1540238171_d94189a0, 10.1021/acs.macromol.7b00665
Format: Citation

Title: Ion Environments in Mn2+ -Doped Polyelectrolyte Complexes: Dilute Magnetic Saloplastics.
Creator: Abhyankar, Nandita, Ghoussoub, Yara E., Wang, Qifeng, Dalal, Naresh S., Schlenoff, Joseph B.
Abstract/Description: Amorphous hydrated complexes of the polyelectrolytes poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium) (PDADMA) were doped with the spin-5/2 ion Mn2+. Xband electron paramagnetic resonance (EPR) measurements of the Mn2+ spins within this stoichiometric polyelectrolyte complex (PEC) revealed an octahedral coordination environment, similar to that observed in aqueous solutions of Mn2+. This octahedral symmetry of the [Mn(H2O)6] 2+ complexes, observed in the fully hydrated PECs, is...
Show moreAmorphous hydrated complexes of the polyelectrolytes poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium) (PDADMA) were doped with the spin-5/2 ion Mn2+. Xband electron paramagnetic resonance (EPR) measurements of the Mn2+ spins within this stoichiometric polyelectrolyte complex (PEC) revealed an octahedral coordination environment, similar to that observed in aqueous solutions of Mn2+. This octahedral symmetry of the [Mn(H2O)6] 2+ complexes, observed in the fully hydrated PECs, is somewhat distorted due to the wide range of ion pairs possible with sulfonate groups on PSS. As the Mn2+ concentration was increased, the linewidths were broadened, indicating the dominance of dipolar broadening over exchange narrowing in determining the linewidths, i.e. any exchange narrowing was masked by the large dipolar broadening. The calculated linewidths were used to estimate the strength of the dipolar interactions, and hence the distances between the Mn2+ spins, based on a simple model of regularly spaced spins. The distances calculated by this method were roughly comparable to the geometric average distances calculated on the basis of the Mn2+ concentrations and densities of the doped PEC samples. From a comparison of their EPR spectra, ion environments in the doped, fully hydrated PECs were found to be similar to those in hydrated classical ion exchange resins. EPR spectra before and after drying of the PECs indicate the replacement of octahedrally coordinated water by oxide anions from the polyanion chain, and the corresponding loss of the symmetric environment of Mn2+ ions.
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Date Issued: 2017-07-01
Identifier: FSU_libsubv1_scholarship_submission_1540239466_01912b85, 10.1021/acs.jpcb.6b02697
Format: Citation

Title: Ferromagnetic Quantum Critical Point In Cepd2p2 With Pd -> Ni Substitution.
Creator: Lai, Y., Bone, S. E., Minasian, S., Ferrier, M. G., Lezama-Pacheco, J., Mocko, V., Ditter, A. S., Kozimor, S. A., Seidler, G. T., Nelson, W. L., Chiu, Y.-C., Huang, K., Potter,...
Show moreLai, Y., Bone, S. E., Minasian, S., Ferrier, M. G., Lezama-Pacheco, J., Mocko, V., Ditter, A. S., Kozimor, S. A., Seidler, G. T., Nelson, W. L., Chiu, Y.-C., Huang, K., Potter, W., Graf, D., Albrecht-Schmitt, T. E., Baumbach, R. E.
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Abstract/Description: An investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd1-x Ni-x)(2)P-2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperature-concentration (T-x) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and Ruderman-KittelKasuya- Yosida (RKKY) interactions, and the introduction...
Show moreAn investigation of the structural, thermodynamic, and electronic transport properties of the isoelectronic chemical substitution series Ce(Pd1-x Ni-x)(2)P-2 is reported, where a possible ferromagnetic quantum critical point is uncovered in the temperature-concentration (T-x) phase diagram. This behavior results from the simultaneous contraction of the unit cell volume, which tunes the relative strengths of the Kondo and Ruderman-KittelKasuya- Yosida (RKKY) interactions, and the introduction of disorder through alloying. Near the critical region at x(cr) approximate to 0.7, the rate of contraction of the unit cell volume strengthens, indicating that the cerium f valence crosses over from trivalent to a noninteger value. Consistent with this picture, x-ray absorption spectroscopy measurements reveal that while CePd2P2 has a purely trivalent cerium f state, CeNi2P2 has a small (<10 %) tetravalent contribution. In a broad region around xcr, there is a breakdown of Fermi-liquid temperature dependences, signaling the influence of quantum critical fluctuations and disorder effects. Measurements of clean CePd2P2 furthermore showthat applied pressure has an initial effect similar to alloying on the ferromagnetic order. From these results, CePd2P2 emerges as a keystone system to test theories such as the Belitz-Kirkpatrick-Vojta model for ferromagnetic quantum criticality, where distinct behaviors are expected in the dirty and clean limits.
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Date Issued: 2018-06-06
Identifier: FSU_libsubv1_wos_000434256700002, 10.1103/PhysRevB.97.224406
Format: Citation

Title: A Rare Positively Charged Nicotinic Acid Disulfide: 2,2 '-dithiodinicotinic Acid Hydrochloride Monohydrate.
Creator: Chemey, Alexander T., McGuire, Chad M., Albrecht-Schmitt, Thomas E.
Abstract/Description: The title compound {systematic name: 3-carboxy-2-[2-(3-carboxypyridin-2-yl)disulfan-1-yl)]pyridin-1-ium chloride monohydrate}, C12H9N2O4S2+center dot Cl-center dot H2O, O, crystallizes in the triclinic space group P (1) over bar. A pair of 2-mercaptonicotinic acid moieties is connected by a 2,2'-disulfide bond with a dihedral angle of 78.79 (3)degrees. One of the N atom is protonated, as are both carboxylate groups, resulting in an overall +1 charge on the dimer. The structure comprises a...
Show moreThe title compound {systematic name: 3-carboxy-2-[2-(3-carboxypyridin-2-yl)disulfan-1-yl)]pyridin-1-ium chloride monohydrate}, C12H9N2O4S2+center dot Cl-center dot H2O, O, crystallizes in the triclinic space group P (1) over bar. A pair of 2-mercaptonicotinic acid moieties is connected by a 2,2'-disulfide bond with a dihedral angle of 78.79 (3)degrees. One of the N atom is protonated, as are both carboxylate groups, resulting in an overall +1 charge on the dimer. The structure comprises a zigzagging layer of the dimerized dithiodinicotinic acid rings, with charge-balancing chloride ions and water molecules between the layers. Hydrogen bonding between the chloride and water sites with the dimer appears to hold the structure together. Nearest neighbor nicotinic acid rings are offset when viewed down the a axis, suggesting no added stability from ring stacking. The asymmetric unit corresponds to the empirical formula of the compound, and it packs with two formula units per unit cell.
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Date Issued: 2018-06-01
Identifier: FSU_libsubv1_wos_000433880900013, 10.1107/S2056989018006916
Format: Citation

Title: Tropical Peatland Carbon Storage Linked To Global Latitudinal Trends In Peat Recalcitrance.
Creator: Hodgkins, Suzanne B., Richardson, Curtis J., Dommain, Rene, Wang, Hongjun, Glaser, Paul H., Verbeke, Brittany, Winkler, B. Rose, Cobb, Alexander R., Rich, Virginia I.,...
Show moreHodgkins, Suzanne B., Richardson, Curtis J., Dommain, Rene, Wang, Hongjun, Glaser, Paul H., Verbeke, Brittany, Winkler, B. Rose, Cobb, Alexander R., Rich, Virginia I., Missilmani, Malak, Flanagan, Neal, Ho, Mengchi, Hoyt, Alison M., Harvey, Charles F., Vining, S. Rose, Hough, Moira A., Moore, Tim R., Richard, Pierre J. H., De la Cruz, Florentino B., Toufaily, Joumana, Hamdan, Rasha, Cooper, William T., Chanton, Jeffrey P.
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Abstract/Description: Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation...
Show morePeatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 degrees C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.
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Date Issued: 2018-09-07
Identifier: FSU_libsubv1_wos_000444014100015, 10.1038/s41467-018-06050-2
Format: Citation

Title: Pathogenic Tfg Mutations Underlying Hereditary Spastic Paraplegia Impair Secretory Protein Trafficking And Axon Fasciculation.
Creator: Slosarek, Erin L., Schuh, Amber L., Pustova, Iryna, Johnson, Adam, Bird, Jennifer, Johnson, Matthew, Frankel, E. B., Bhattacharya, Nilakshee, Hanna, Michael G., Burke, Jordan E....
Show moreSlosarek, Erin L., Schuh, Amber L., Pustova, Iryna, Johnson, Adam, Bird, Jennifer, Johnson, Matthew, Frankel, E. B., Bhattacharya, Nilakshee, Hanna, Michael G., Burke, Jordan E., Ruhl, David A., Quinney, Kyle, Block, Samuel, Peotter, Jennifer L., Chapman, Edwin R., Sheets, Michael D., Butcher, Samuel E., Stagg, Scott M., Audhya, Anjon
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Abstract/Description: Length-dependent axonopathy of the corticospinal tract causes lower limb spasticity and is characteristic of several neurological disorders, including hereditary spastic paraplegia (HSP) and amyotrophic lateral sclerosis. Mutations in Trk-fused gene (TFG) have been implicated in both diseases, but the pathomechanisms by which these alterations cause neuropathy remain unclear. Here, we biochemically and genetically define the impact of a mutation within the TFG coiled-coil domain, which...
Show moreLength-dependent axonopathy of the corticospinal tract causes lower limb spasticity and is characteristic of several neurological disorders, including hereditary spastic paraplegia (HSP) and amyotrophic lateral sclerosis. Mutations in Trk-fused gene (TFG) have been implicated in both diseases, but the pathomechanisms by which these alterations cause neuropathy remain unclear. Here, we biochemically and genetically define the impact of a mutation within the TFG coiled-coil domain, which underlies early-onset forms of HSP. We find that the TFG (p.R106C) mutation alters compaction of TFG ring complexes, which play a critical role in the export of cargoes from the endoplasmic reticulum (ER). Using CRISPR-mediated genome editing, we engineered human stem cells that express the mutant form of TFG at endogenous levels and identified specific defects in secretion from the ER and axon fasciculation following neuronal differentiation. Together, our data highlight a key role for TFG-mediated protein transport in the pathogenesis of HSP.
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Date Issued: 2018-08-28
Identifier: FSU_libsubv1_wos_000442923900005, 10.1016/j.celrep.2018.07.081
Format: Citation

Title: (tco4-)-tc-99 Remediation By A Cationic Polymeric Network.
Creator: Li, Jie, Dai, Xing, Zhu, Lin, Xu, Chao, Zhang, Duo, Silver, Mark A., Li, Peng, Chen, Lanhua, Li, Yongzhong, Zuo, Douwen, Zhang, Hui, Xiao, Chengliang, Chen, Jing, Diwu, Juan,...
Show moreLi, Jie, Dai, Xing, Zhu, Lin, Xu, Chao, Zhang, Duo, Silver, Mark A., Li, Peng, Chen, Lanhua, Li, Yongzhong, Zuo, Douwen, Zhang, Hui, Xiao, Chengliang, Chen, Jing, Diwu, Juan, Farha, Omar K., Albrecht-Schmitt, Thomas E., Chai, Zhifang, Wang, Shuao
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Abstract/Description: Direct removal of (TcO4-)-Tc-99 from the highly acidic solution of used nuclear fuel is highly beneficial for the recovery of uranium and plutonium and more importantly aids in the elimination of Tc-99 discharge into the environment. However, this task represents a huge challenge given the combined extreme conditions of super acidity, high ionic strength, and strong radiation field. Here we overcome this challenge using a cationic polymeric network with significant TcO4- uptake capabilities...
Show moreDirect removal of (TcO4-)-Tc-99 from the highly acidic solution of used nuclear fuel is highly beneficial for the recovery of uranium and plutonium and more importantly aids in the elimination of Tc-99 discharge into the environment. However, this task represents a huge challenge given the combined extreme conditions of super acidity, high ionic strength, and strong radiation field. Here we overcome this challenge using a cationic polymeric network with significant TcO4- uptake capabilities in four aspects: the fastest sorption kinetics, the highest sorption capacity, the most promising uptake performance from highly acidic solutions, and excellent radiation-resistance and hydrolytic stability among all anion sorbent materials reported. In addition, this material is fully recyclable for multiple sorption/desorption trials, making it extremely attractive for waste partitioning and emergency remediation. The excellent TcO4- uptake capability is elucidated by X-ray absorption spectroscopy, solid-state NMR measurement, and density functional theory analysis on anion coordination and bonding.
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Date Issued: 2018-08-01
Identifier: FSU_libsubv1_wos_000440413500007, 10.1038/s41467-018-05380-5
Format: Citation

Title: Diffusion of Sites versus Polymers in Polyelectrolyte Complexes and Multilayers.
Creator: Fares, Hadi, Schlenoff, Joseph
Abstract/Description: It has long been assumed that the spontaneous formation of materials such as complexes and multilayers from charged polymers depends on (inter)diffusion of these polyelectrolytes. Here, we separately examine the mass transport of polymer molecules and extrinsic sites—charged polyelectrolyte repeat units balanced by counterions—within thin films of polyelectrolyte complex, PEC, using sensitive isotopic labeling techniques. The apparent diffusion coefficients of these sites within PEC films of...
Show moreIt has long been assumed that the spontaneous formation of materials such as complexes and multilayers from charged polymers depends on (inter)diffusion of these polyelectrolytes. Here, we separately examine the mass transport of polymer molecules and extrinsic sites—charged polyelectrolyte repeat units balanced by counterions—within thin films of polyelectrolyte complex, PEC, using sensitive isotopic labeling techniques. The apparent diffusion coefficients of these sites within PEC films of poly(diallyldimethylammonium), PDADMA, and poly(styrenesulfonate), PSS, are at least 2 orders of magnitude faster than the diffusion of polyelectrolytes themselves. This is because site diffusion requires only local rearrangements of polyelectrolyte repeat units, placing far fewer kinetic limitations on the assembly of polyelectrolyte complexes in all of their forms. Site diffusion strongly depends on the salt concentration (ionic strength) of the environment, and diffusion of PDADMA sites is faster than that of PSS sites, accounting for the asymmetric nature of multilayer growth. Site diffusion is responsible for multilayer growth in the linear and into the exponential regimes, which explains how PDADMA can mysteriously “pass through” layers of PSS. Using quantitative relationships between site diffusion coefficient and salt concentration, conditions were identified that allowed the diffusion length to always exceed the film thickness, leading to full exponential growth over 3 orders of magnitude thickness. Both site and polymer diffusion were independent of molecular weight, suggesting that ion pairing density is a limiting factor. Polyelectrolyte complexes are examples of a broader class of dynamic bulk polymeric materials that (self-) assemble via the transport of cross-links or defects rather than actual molecules.
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Date Issued: 2017-10-05
Identifier: FSU_libsubv1_scholarship_submission_1543269470_f050f9b2, 10.1021/jacs.7b07905
Format: Citation

Title: Driving Forces for Oppositely Charged Polyioon Association in Aqueous Solution: Enthalpic, Entropic but Not Electrostatic.
Creator: Fu, Jingcheng, Schlenoff, Joseph
Abstract/Description: Driving forces for association between oppositely charged biological or synthetic polymers in aqueous solution have long been identified as electrostatic in origin. This attraction is broken down into an entropic component, due to loss of counterions, and an enthalpic component, stemming from Coulombic attraction between opposite charges. While the balance between entropic and enthalpic contributions shifts according to the conditions, the presence of exotherms or endotherms on mixing, though...
Show moreDriving forces for association between oppositely charged biological or synthetic polymers in aqueous solution have long been identified as electrostatic in origin. This attraction is broken down into an entropic component, due to loss of counterions, and an enthalpic component, stemming from Coulombic attraction between opposite charges. While the balance between entropic and enthalpic contributions shifts according to the conditions, the presence of exotherms or endotherms on mixing, though small, are viewed as signatures of Coulombic interactions which support theories of polyelectrolyte association rooted in continuum electrostatics. Here, a head-to-head comparison is made between mechanisms based on electrostatics and those based on specific ion pairing, or ion exchange. Using a Hofmeister series of counterions for a common polycation, poly(diallyldimethylammonium), enthalpy changes on association with poly(styrenesulfonate) are shown to derive from changes in water perturbation, revealed by Raman scattering studies of water O–H vibrations. The free energy for complexation is almost completely entropic over all salt concentrations.
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Date Issued: 2016-01-15
Identifier: FSU_libsubv1_scholarship_submission_1543268476_8c636203, 10.1021/jacs.5b11878
Format: Citation

Title: Saloplastics: Processing Compact Polyelectrolyte Complexes.
Creator: Schlenoff, Joseph, Schaaf, Pierre
Abstract/Description: Polyelectrolyte complexes (PECs) are prepared by mixing solutions of oppositely charged polyelectrolytes. These diffuse, amorphous precipitates may be compacted into dense materials, CoPECs, by ultracentrifugation (ucPECs) or extrusion (exPECs). The presence of salt water is essential in plasticizing PECs to allow them to be reformed and fused. When hydrated, CoPECs are versatile, rugged, biocompatible, elastic materials with applications including bioinspired materials, supports for enzymes...
Show morePolyelectrolyte complexes (PECs) are prepared by mixing solutions of oppositely charged polyelectrolytes. These diffuse, amorphous precipitates may be compacted into dense materials, CoPECs, by ultracentrifugation (ucPECs) or extrusion (exPECs). The presence of salt water is essential in plasticizing PECs to allow them to be reformed and fused. When hydrated, CoPECs are versatile, rugged, biocompatible, elastic materials with applications including bioinspired materials, supports for enzymes and (nano)composites. In this review, various methods for making CoPECs are described, as well as fundamental responses of CoPEC mechanical properties to salt concentration. Possible applications as synthetic cartilage, enzymatically active biocomposites, self‐healing materials, and magnetic nanocomposites are presented.
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Date Issued: 2015-03-13
Identifier: FSU_libsubv1_scholarship_submission_1543268228_25a15aaa, 10.1002/adma.201500176
Format: Citation

Title: Janus Nanofilms.
Creator: Ghoussoub, Yara, Schlenoff, Joseph
Abstract/Description: To make a two-dimensional Janus object, the perfluorinated anionic polyelectrolyte Nafion was adsorbed to the surface of ultrathin films of polyelectrolyte complex. Nafion changed the wetting characteristics of the polyelectrolyte multilayer (PEMU) of poly(diallyldimethylammonium) and poly(styrenesulfonate) from hydrophilic to hydrophobic. PEMUs assembled on aluminum substrates and terminated with Nafion could be released by exposure to alkali solution, producing free-floating films in the...
Show moreTo make a two-dimensional Janus object, the perfluorinated anionic polyelectrolyte Nafion was adsorbed to the surface of ultrathin films of polyelectrolyte complex. Nafion changed the wetting characteristics of the polyelectrolyte multilayer (PEMU) of poly(diallyldimethylammonium) and poly(styrenesulfonate) from hydrophilic to hydrophobic. PEMUs assembled on aluminum substrates and terminated with Nafion could be released by exposure to alkali solution, producing free-floating films in the 100 nm thickness regime. Water contact angle measurements showed a strong difference in hydrophilicity between the two sides of this Janus film, which was further characterized using atomic force microscopy and X-ray photoelectron spectroscopy (XPS). XPS revealed different fluorine contents on both sides of the PEMU, which could be translated to a Nafion gradient through the film. Fourier transform infrared spectroscopy showed the Nafion-containing films were much more resistant to decomposition by high salt concentration.
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Date Issued: 2016-04-07
Identifier: FSU_libsubv1_scholarship_submission_1543269187_3ddc9070, 10.1021/acs.langmuir.6b00672
Format: Citation

Title: Cell Resistant Zwitterionic Polyelectrolyte Coating Promotes Bacterial Attachment: and Adhesion Contradiction.
Creator: Martinez, Jessica, Kelly, Kris, Ghoussoub, Yara, Delgado, David, Keller, Thomas, Schlenoff, Joseph
Abstract/Description: AbstractPolymers of various architectures with zwitterionic functionality have recently been shown to effectively suppress nonspecific fouling of surfaces by proteins and prokaryotic (bacteria) or eukaryotic (mammalian) cells as well as other microorganisms and environmental contaminants. In this work, zwitterionic copolymers were used to make thin coatings on substrates with the layer-by-layer method. Polyelectrolyte multilayers, PEMUs, were built with [poly(allylamine hydrochloride)], PAH,...
Show moreAbstractPolymers of various architectures with zwitterionic functionality have recently been shown to effectively suppress nonspecific fouling of surfaces by proteins and prokaryotic (bacteria) or eukaryotic (mammalian) cells as well as other microorganisms and environmental contaminants. In this work, zwitterionic copolymers were used to make thin coatings on substrates with the layer-by-layer method. Polyelectrolyte multilayers, PEMUs, were built with [poly(allylamine hydrochloride)], PAH, and copolymers of acrylic acid and either the AEDAPS zwitterionic group 3-[2-(acrylamido)-ethyldimethyl ammonio] propane sulfonate (PAA-co-AEDAPS), or benzophenone (PAABp). Benzophenone allowed the PEMU to be toughened by photocrosslinking post-deposition. The attachment of two mammalian cell lines, rat aortic smooth muscle (A7r5) and mouse fibroblasts (3T3), and the biofilm-forming Gram-negative bacteria Escherichia coli was studied on PEMUs terminated with PAA-co-AEDAPS. Consistent with earlier studies, it is shown that PAH/PAA-co-AEDAPS PEMUs resist the adhesion of mammalian cells, but, contrary to our initial hypothesis, are bacterial adhesive and significantly so after maximizing the surface presentation of PAA-co-AEDAPS. This unexpected contrast in the adhesive behavior of prokaryotic and eukaryotic cells is explained by differences in adhesion mechanisms as well as different responses to the topology and morphology of the multilayer surface.
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Date Issued: 2016-02-12
Identifier: FSU_libsubv1_scholarship_submission_1543268983_2542ae09, 10.1039/C5BM00585J
Format: Citation

Title: The Polyelectrolyte Complex/Coacervate Continuum.
Creator: Schlenoff, Joseph, Wang, Qifeng
Abstract/Description: Stoichiometric polyelectrolyte complexes (PECs) of the strong polyelectrolytes poly(styrenesulfonate) (PSS) and poly(diallyldimethylammonium) (PDADMA) were dissociated and dissolved in aqueous KBr. Water was added to dilute the salt, allowing polyelectrolytes to reassociate. After appropriate equilibration, these mixtures yielded compositions spanning complexes (solid) to coacervates (elastic liquid) to dissolved solutions with increasing [KBr]. These compositions were defined by a ternary...
Show moreStoichiometric polyelectrolyte complexes (PECs) of the strong polyelectrolytes poly(styrenesulfonate) (PSS) and poly(diallyldimethylammonium) (PDADMA) were dissociated and dissolved in aqueous KBr. Water was added to dilute the salt, allowing polyelectrolytes to reassociate. After appropriate equilibration, these mixtures yielded compositions spanning complexes (solid) to coacervates (elastic liquid) to dissolved solutions with increasing [KBr]. These compositions were defined by a ternary polymer/water/salt phase diagram. For coacervates, transient microphase separation could be induced by a small departure from equilibration temperature. A boundary between complex and coacervate states was defined by the crossover point between loss and storage modulus. Salt ions within the complex/coacervate were identified as either ion paired with polyelectrolytes (“doping”) or unassociated. The fraction of ion pair cross-links between polyelectrolytes as a function of KBr concentration was used to account for viscosity using a model of “sticky” reptation.
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Date Issued: 2014-04-28
Identifier: FSU_libsubv1_scholarship_submission_1543267595_f3eff53c, 10.1021/ma500500q
Format: Citation

Title: One-dimensional organic lead halide perovskites with efficient bluish white-light emission.
Creator: Yuan, Zhao, Zhou, Chenkun, Tian, Yu, Shu, Yu, Messier, Joshua, Wang, Jamie C, van de Burgt, Lambertus J, Kountouriotis, Konstantinos, Xin, Yan, Holt, Ethan, Schanze, Kirk, Clark...
Show moreYuan, Zhao, Zhou, Chenkun, Tian, Yu, Shu, Yu, Messier, Joshua, Wang, Jamie C, van de Burgt, Lambertus J, Kountouriotis, Konstantinos, Xin, Yan, Holt, Ethan, Schanze, Kirk, Clark, Ronald, Siegrist, Theo, Ma, Biwu
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Abstract/Description: Organic-inorganic hybrid metal halide perovskites, an emerging class of solution processable photoactive materials, welcome a new member with a one-dimensional structure. Herein we report the synthesis, crystal structure and photophysical properties of one-dimensional organic lead bromide perovskites, CNHPbBr, in which the edge sharing octahedral lead bromide chains [PbBr ] are surrounded by the organic cations CNH to form the bulk assembly of core-shell quantum wires. This unique one...
Show moreOrganic-inorganic hybrid metal halide perovskites, an emerging class of solution processable photoactive materials, welcome a new member with a one-dimensional structure. Herein we report the synthesis, crystal structure and photophysical properties of one-dimensional organic lead bromide perovskites, CNHPbBr, in which the edge sharing octahedral lead bromide chains [PbBr ] are surrounded by the organic cations CNH to form the bulk assembly of core-shell quantum wires. This unique one-dimensional structure enables strong quantum confinement with the formation of self-trapped excited states that give efficient bluish white-light emissions with photoluminescence quantum efficiencies of approximately 20% for the bulk single crystals and 12% for the microscale crystals. This work verifies once again that one-dimensional systems are favourable for exciton self-trapping to produce highly efficient below-gap broadband luminescence, and opens up a new route towards superior light emitters based on bulk quantum materials.
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Date Issued: 2017-01-04
Identifier: FSU_pmch_28051092, 10.1038/ncomms14051, PMC5216108, 28051092, 28051092, ncomms14051
Format: Citation

Title: Variational optimization of the two-electron reduced-density matrix under pure-state N-representability conditions.
Creator: DePrince, A. Eugene
Abstract/Description: The direct variational optimization of the ground-state two-electron reduced-density matrix (2-RDM) is typically performed under ensemble N-representability conditions. Accordingly, variationally obtained 2-RDMs for degenerate ground states may not represent a pure state. When considering only ground-state energetics, the ensemble nature of the 2-RDM is of little consequence. However, the use of ensemble densities within an extended random phase approximation (ERPA) yields astonishingly poor...
Show moreThe direct variational optimization of the ground-state two-electron reduced-density matrix (2-RDM) is typically performed under ensemble N-representability conditions. Accordingly, variationally obtained 2-RDMs for degenerate ground states may not represent a pure state. When considering only ground-state energetics, the ensemble nature of the 2-RDM is of little consequence. However, the use of ensemble densities within an extended random phase approximation (ERPA) yields astonishingly poor estimates of excitation energies, even for simple atomic systems [H. van Aggelen et al., Comput. Theor. Chem. 1003, 50-54 (2013)]. Here, we outline an approach for the direct variational optimization of ground-state 2-RDMs that satisfy pure-state N-representability known as generalized Pauli constraints. Within the ERPA, 2-RDMs that satisfy both ensemble conditions and the generalized Pauli constraints yield much more reliable estimates of excitation energies than those that satisfy only ensemble conditions. Published by AIP Publishing.
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Date Issued: 2016-10-28
Identifier: FSU_libsubv1_wos_000387586200014, 10.1063/1.4965888
Format: Citation

Title: Unfolding the physics of URu2Si2 through silicon to phosphorus substitution.
Creator: Gallagher, A., Chen, K.-W., Moir, C. M., Cary, S. K., Kametani, F., Kikugawa, N., Graf, D., Albrecht-Schmitt, T. E., Riggs, S. C., Shekhter, A., Baumbach, R. E.
Abstract/Description: The heavy fermion intermetallic compound URu2Si2 exhibits a hidden-order phase below the temperature of 17.5 K, which supports both anomalous metallic behavior and unconventional superconductivity. While these individual phenomena have been investigated in detail, it remains unclear how they are related to each other and to what extent uranium f-electron valence fluctuations influence each one. Here we use ligand site substituted URu2Si2-xPx to establish their evolution under electronic...
Show moreThe heavy fermion intermetallic compound URu2Si2 exhibits a hidden-order phase below the temperature of 17.5 K, which supports both anomalous metallic behavior and unconventional superconductivity. While these individual phenomena have been investigated in detail, it remains unclear how they are related to each other and to what extent uranium f-electron valence fluctuations influence each one. Here we use ligand site substituted URu2Si2-xPx to establish their evolution under electronic tuning. We find that while hidden order is monotonically suppressed and destroyed for x <= 0.035, the superconducting strength evolves non-monotonically with a maximum near x approximate to 0.01 and that superconductivity is destroyed near x approximate to 0.028. This behavior reveals that hidden order depends strongly on tuning outside of the U f-electron shells. It also suggests that while hidden order provides an environment for superconductivity and anomalous metallic behavior, it's fluctuations may not be solely responsible for their progression.
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Date Issued: 2016-02
Identifier: FSU_libsubv1_wos_000371035200013, 10.1038/ncomms10712
Format: Citation

Title: Zn(II)-coordination modulated ligand photophysical processes – the development of fluorescent indicators for imaging biological Zn(II) ions.
Creator: Zhu, Lei, Yuan, Zhao, Simmons, J., Sreenath, Kesavapillai
Abstract/Description: Molecular photophysics and metal coordination chemistry are the two fundamental pillars that support the development of fluorescent cation indicators. In this article, we describe how Zn(II)-coordination alters various ligand-centered photophysical processes that are pertinent to developing Zn(II) indicators. The main aim is to show how small organic Zn(II) indicators work under the constraints of specific requirements, including Zn(II) detection range, photophysical requirements such as...
Show moreMolecular photophysics and metal coordination chemistry are the two fundamental pillars that support the development of fluorescent cation indicators. In this article, we describe how Zn(II)-coordination alters various ligand-centered photophysical processes that are pertinent to developing Zn(II) indicators. The main aim is to show how small organic Zn(II) indicators work under the constraints of specific requirements, including Zn(II) detection range, photophysical requirements such as excitation energy and emission color, temporal and spatial resolutions in a heterogeneous intracellular environment, and fluorescence response selectivity between similar cations such as Zn(II) and Cd(II). In the last section, the biological questions that fluorescent Zn(II) indicators help to answer are described, which have been motivating and challenging this field of research.
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Date Issued: 2014
Identifier: FSU_migr_chm_faculty_publications-0016, 10.1039/C4RA00354C
Format: Citation

Title: Identification and Characterization of Human Proteoforms by Top-Down LC-21 Tesla FT-ICR Mass Spectrometry.
Creator: Anderson, Lissa C, DeHart, Caroline J, Kaiser, Nathan K, Fellers, Ryan T, Smith, Donald F, Greer, Joseph B, LeDuc, Richard D, Blakney, Greg T, Thomas, Paul M, Kelleher, Neil L,...
Show moreAnderson, Lissa C, DeHart, Caroline J, Kaiser, Nathan K, Fellers, Ryan T, Smith, Donald F, Greer, Joseph B, LeDuc, Richard D, Blakney, Greg T, Thomas, Paul M, Kelleher, Neil L, Hendrickson, Christopher L
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Abstract/Description: Successful high-throughput characterization of intact proteins from complex biological samples by mass spectrometry requires instrumentation capable of high mass resolving power, mass accuracy, sensitivity, and spectral acquisition rate. These limitations often necessitate the performance of hundreds of LC-MS/MS experiments to obtain reasonable coverage of the targeted proteome, which is still typically limited to molecular weights below 30 kDa. The National High Magnetic Field Laboratory ...
Show moreSuccessful high-throughput characterization of intact proteins from complex biological samples by mass spectrometry requires instrumentation capable of high mass resolving power, mass accuracy, sensitivity, and spectral acquisition rate. These limitations often necessitate the performance of hundreds of LC-MS/MS experiments to obtain reasonable coverage of the targeted proteome, which is still typically limited to molecular weights below 30 kDa. The National High Magnetic Field Laboratory (NHMFL) recently installed a 21 T FT-ICR mass spectrometer, which is part of the NHMFL FT-ICR User Facility and available to all qualified users. Here we demonstrate top-down LC-21 T FT-ICR MS/MS of intact proteins derived from human colorectal cancer cell lysate. We identified a combined total of 684 unique protein entries observed as 3238 unique proteoforms at a 1% false discovery rate, based on rapid, data-dependent acquisition of collision-induced and electron-transfer dissociation tandem mass spectra from just 40 LC-MS/MS experiments. Our identifications included 372 proteoforms with molecular weights over 30 kDa detected at isotopic resolution, which substantially extends the accessible mass range for high-throughput top-down LC-MS/MS.
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Date Issued: 2017-02-03
Identifier: FSU_pmch_27936753, 10.1021/acs.jproteome.6b00696, PMC5353847, 27936753, 27936753
Format: Citation

Title: Probing Hydronium Ion Histidine NH Exchange Rate Constants in the M2 Channel via Indirect Observation of Dipolar-Dephased N Signals in Magic-Angle-Spinning NMR.
Creator: Fu, Riqiang, Miao, Yimin, Qin, Huajun, Cross, Timothy A
Abstract/Description: Water-protein chemical exchange in membrane-bound proteins is an important parameter for understanding how proteins interact with their aqueous environment, but has been difficult to observe in membrane-bound biological systems. Here, we demonstrate the feasibility of probing specific water-protein chemical exchange in membrane-bound proteins in solid-state MAS NMR. By spin-locking the H magnetization along the magic angle, the H spin diffusion is suppressed such that a water-protein chemical...
Show moreWater-protein chemical exchange in membrane-bound proteins is an important parameter for understanding how proteins interact with their aqueous environment, but has been difficult to observe in membrane-bound biological systems. Here, we demonstrate the feasibility of probing specific water-protein chemical exchange in membrane-bound proteins in solid-state MAS NMR. By spin-locking the H magnetization along the magic angle, the H spin diffusion is suppressed such that a water-protein chemical exchange process can be monitored indirectly by dipolar-dephased N signals through polarization transfer from H. In the example of the Influenza A full length M2 protein, the buildup of dipolar-dephased N signals from the tetrad of His37 side chains have been observed as a function of spin-lock time. This confirms that hydronium ions are in exchange with protons in the His37 NH bonds at the heart of the M2 proton conduction mechanism, with an exchange rate constant of ∼1750 s for pH 6.2 at -10 °C.
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Date Issued: 2016-12-14
Identifier: FSU_pmch_27960325, 10.1021/jacs.6b08376, PMC5368641, 27960325, 27960325
Format: Citation

Title: Self-organization In Precipitation Reactions Far From The Equilibrium.
Creator: Nakouzi, Elias, Steinbock, Oliver
Abstract/Description: Far from the thermodynamic equilibrium, many precipitation reactions create complex product structures with fascinating features caused by their unusual origins. Unlike the dissipative patterns in other self-organizing reactions, these features can be permanent, suggesting potential applications in materials science and engineering. We review four distinct classes of precipitation reactions, describe similarities and differences, and discuss related challenges for theoretical studies. These...
Show moreFar from the thermodynamic equilibrium, many precipitation reactions create complex product structures with fascinating features caused by their unusual origins. Unlike the dissipative patterns in other self-organizing reactions, these features can be permanent, suggesting potential applications in materials science and engineering. We review four distinct classes of precipitation reactions, describe similarities and differences, and discuss related challenges for theoretical studies. These classes are hollow micro- and macrotubes in chemical gardens, polycrystalline silica carbonate aggregates (biomorphs), Liesegang bands, and propagating precipitation-dissolution fronts. In many cases, these systems show intricate structural hierarchies that span from the nanometer scale into the macroscopic world. We summarize recent experimental progress that often involves growth under tightly regulated conditions by means of wet stamping, holographic heating, and controlled electric, magnetic, or pH perturbations. In this research field, progress requires mechanistic insights that cannot be derived from experiments alone. We discuss how mesoscopic aspects of the product structures can be modeled by reaction-transport equations and suggest important targets for future studies that should also include materials features at the nanoscale.
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Date Issued: 2016-08
Identifier: FSU_libsubv1_wos_000383734300047, 10.1126/sciadv.1601144
Format: Citation

Title: Transport, magnetic, and optical properties of electrochemically doped poly(1, 4-dimethoxy phenylene vinylene).
Creator: Schlenoff, Joseph B., Obrzut, Jan, Karasz, F.
Abstract/Description: A coordinated study on electrochemical, magnetic, optical, and transport properties of poly(1, 4- dimethoxy phenylene vinylene) (PDMPV) using in situ electrochemical doping techniques is presented. Properties are correlated through a common axis of applied voltage. Electrochemical doping shows approx. 100% Coulombic efficiency up to an applied potential of 3.8 V versus lithium in propylene carbonate electrolyte. Conductivity increases in a reversible manner to a maximum of 250 0 ' cm ' and an...
Show moreA coordinated study on electrochemical, magnetic, optical, and transport properties of poly(1, 4- dimethoxy phenylene vinylene) (PDMPV) using in situ electrochemical doping techniques is presented. Properties are correlated through a common axis of applied voltage. Electrochemical doping shows approx. 100% Coulombic efficiency up to an applied potential of 3.8 V versus lithium in propylene carbonate electrolyte. Conductivity increases in a reversible manner to a maximum of 250 0 ' cm ' and an applied potential of 3.9 V. Potentials in excess of 3.9 V cause an irreversible decrease in conductivity. Spin and charge show a 1:1 relation on/y to very low doping levels. Two paramagnetic species are produced on doping. A maximum spin concentration is observed at =3.7 V. The ultraviolet —visible —near-infrared spectra of doped PDMPV show at least five absorption bands, at 4.8, 3.7, 2.5, 1.7, and 0.6 eV. The first three bands decrease with doping and the latter two increase. When analyzed by the polaron or bipolaron model, the optical data imply significant symmetry breaking, Contributions to the optical activity from polarons and bipolarons are determined from the EPR results and are found to be di6'erent for both peaks, implying greater symmetrybreaking eA'ects for polarons. An electrochemical analysis of EPR results suggests that polaron interaction energies are =0.4S eV greater than those for bipolarons.
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Date Issued: 1989
Identifier: FSU_migr_chm_faculty_publications-0006
Format: Citation

Title: Upregulation Of Minichromosome Maintenance Complex Component 3 During Epithelial-to-mesenchymal Transition In Human Prostate Cancer.
Creator: Stewart, Paul A., Khamis, Zahraa I., Zhau, Haiyen E., Duan, Peng, Li, Quanlin, Chung, Leland W. K., Sang, Qing-Xiang Amy
Abstract/Description: Metastasis is often associated with epithelial-to-mesenchymal transition (EMT). To understand the molecular mechanisms of this process, we conducted proteomic analysis of androgen-repressed cancer of the prostate (ARCaP), an experimental model of metastatic human prostate cancer. The protein signatures of epithelial (ARCaP(E)) and mesenchymal (ARCaPM) cells were consistent with their phenotypes. Importantly, the expression of mini-chromosome maintenance 3 (MCM3) protein, a crucial subunit of...
Show moreMetastasis is often associated with epithelial-to-mesenchymal transition (EMT). To understand the molecular mechanisms of this process, we conducted proteomic analysis of androgen-repressed cancer of the prostate (ARCaP), an experimental model of metastatic human prostate cancer. The protein signatures of epithelial (ARCaP(E)) and mesenchymal (ARCaPM) cells were consistent with their phenotypes. Importantly, the expression of mini-chromosome maintenance 3 (MCM3) protein, a crucial subunit of DNA helicase, was significantly higher in ARCaP(M) cells than that of ARCaP(E) cells. This increased MCM3 protein expression level was verified using Western blot analysis of the ARCaP cell lineages. Furthermore, immunohistochemical analysis of MCM3 protein levels in human prostate tissue specimens showed elevated expression in bone metastasis and advanced human prostate cancer tissue samples. Subcutaneous injection experiments using ARCaP(E) and ARCaP(M) cells in a mouse model also revealed increased MCM3 protein levels in mesenchymal-derived tumors. This study identifies MCM3 as an upregulated molecule in mesenchymal phenotype of human prostate cancer cells and advanced human prostate cancer specimens, suggesting MCM3 may be a new potential drug target for prostate cancer treatment.
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Date Issued: 2017-06-13
Identifier: FSU_libsubv1_wos_000403311900096, 10.18632/oncotarget.16835
Format: Citation

Title: Margatoxin-bound quantum dots as a novel inhibitor of the voltage-gated ion channel Kv1.3.
Creator: Schwartz, Austin B, Kapur, Anshika, Wang, Wentao, Huang, Zhenbo, Fardone, Erminia, Palui, Goutam, Mattoussi, Hedi, Fadool, Debra Ann
Abstract/Description: Venom-derived ion channel inhibitors have strong channel selectivity, potency, and stability; however, tracking delivery to their target can be challenging. Herein, we utilized luminescent quantum dots (QDs) conjugated to margatoxin (MgTx) as a traceable vehicle to target a voltage-dependent potassium channel, Kv1.3, which has a select distribution and well-characterized role in immunity, glucose metabolism, and sensory ability. We screened both unconjugated (MgTx) and conjugated MgTx (QD...
Show moreVenom-derived ion channel inhibitors have strong channel selectivity, potency, and stability; however, tracking delivery to their target can be challenging. Herein, we utilized luminescent quantum dots (QDs) conjugated to margatoxin (MgTx) as a traceable vehicle to target a voltage-dependent potassium channel, Kv1.3, which has a select distribution and well-characterized role in immunity, glucose metabolism, and sensory ability. We screened both unconjugated (MgTx) and conjugated MgTx (QD-MgTx) for their ability to inhibit Shaker channels Kv1.1 to Kv1.7 using patch-clamp electrophysiology in HEK293 cells. Our data indicate that MgTx inhibits 79% of the outward current in Kv1.3-transfected cells and that the QD-MgTx conjugate is able to achieve a similar level of block, albeit a slightly reduced efficacy (66%) and at a slower time course (50% block by 10.9 ± 1.1 min, MgTx; vs. 15.3 ± 1.2 min, QD-MgTx). Like the unbound peptide, the QD-MgTx conjugate inhibits both Kv1.3 and Kv1.2 at a 1 nM concentration, whereas it does not inhibit other screened Shaker channels. We tested the ability of QD-MgTx to inhibit native Kv1.3 expressed in the mouse olfactory bulb (OB). In brain slices of the OB, the conjugate acted similarly to MgTx to inhibit Kv1.3, causing an increased action potential firing frequency attributed to decreased intraburst duration rather than interspike interval. Our data demonstrate a retention of known biophysical properties associated with block of the vestibule of Kv1.3 by QD-MgTx conjugate compared to that of MgTx, inferring QDs could provide a useful tool to deliver ion channel inhibitors to targeted tissues in vivo.
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Date Issued: 2017-02-01
Identifier: FSU_pmch_27861889, 10.1111/jnc.13891, PMC5250575, 27861889, 27861889
Format: Citation

Title: Evidence for a Proapoptotic Role of Matrix Metalloproteinase-26 in Human Prostate Cancer Cells and Tissues.
Creator: Khamis, Zahraa I, Iczkowski, Kenneth A, Man, Yan-Gao, Bou-Dargham, Mayassa J, Sang, Qing-Xiang Amy
Abstract/Description: Matrix metalloproteinases (MMPs) play intricate roles in cancer progression; some promote invasion and angiogenesis while others suppress tumor growth. For example, human MMP-26/endometase/matrilysin-2 was reported to be either protective or pro-tumorigenic. Our previous reports suggested pro-invasion and anti-inflammation properties in prostate cancer. Here, we provide evidence for a protective role of MMP-26 in the prostate. MMP-26 expression levels in androgen-repressed human prostate...
Show moreMatrix metalloproteinases (MMPs) play intricate roles in cancer progression; some promote invasion and angiogenesis while others suppress tumor growth. For example, human MMP-26/endometase/matrilysin-2 was reported to be either protective or pro-tumorigenic. Our previous reports suggested pro-invasion and anti-inflammation properties in prostate cancer. Here, we provide evidence for a protective role of MMP-26 in the prostate. MMP-26 expression levels in androgen-repressed human prostate cancer (ARCaP) cells, transfected with sense or anti-sense MMP-26 cDNA, are directly correlated with those of the pro-apoptotic marker Bax. Immunohistochemical staining of prostate cancer tissue samples shows similar protein expression patterns, correlating the expression levels of MMP-26 and Bax in benign, neoplastic, and invasive prostate cancer tissues. The MMP-26 protein levels were upregulated in high grade prostate intraepithelial neoplasia (HGPIN) and decreased during the course of disease progression. Further analysis using an indirect terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay showed that many tumor cells expressing MMP-26 were undergoing apoptosis. This study showed that the high level of MMP-26 expression is positively correlated with the presence of apoptotic cells. This pro-apoptotic role of MMP-26 in human prostate cancer cells and tissues may enhance our understanding of the paradoxical roles of MMP-26 in tumor invasion and progression.
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Date Issued: 2016-01-01
Identifier: FSU_pmch_26722363, 10.7150/jca.13067, PMC4679384, 26722363, 26722363, jcav07p0080
Format: Citation

Title: Bipartite recognition of target RNAs activates DNA cleavage by the Type III-B CRISPR-Cas system.
Creator: Elmore, Joshua R, Sheppard, Nolan F, Ramia, Nancy, Deighan, Trace, Li, Hong, Terns, Rebecca M, Terns, Michael P
Abstract/Description: CRISPR-Cas systems eliminate nucleic acid invaders in bacteria and archaea. The effector complex of the Type III-B Cmr system cleaves invader RNAs recognized by the CRISPR RNA (crRNA ) of the complex. Here we show that invader RNAs also activate the Cmr complex to cleave DNA. As has been observed for other Type III systems, Cmr eliminates plasmid invaders in Pyrococcus furiosus by a mechanism that depends on transcription of the crRNA target sequence within the plasmid. Notably, we found that...
Show moreCRISPR-Cas systems eliminate nucleic acid invaders in bacteria and archaea. The effector complex of the Type III-B Cmr system cleaves invader RNAs recognized by the CRISPR RNA (crRNA ) of the complex. Here we show that invader RNAs also activate the Cmr complex to cleave DNA. As has been observed for other Type III systems, Cmr eliminates plasmid invaders in Pyrococcus furiosus by a mechanism that depends on transcription of the crRNA target sequence within the plasmid. Notably, we found that the target RNA per se induces DNA cleavage by the Cmr complex in vitro. DNA cleavage activity does not depend on cleavage of the target RNA but notably does require the presence of a short sequence adjacent to the target sequence within the activating target RNA (rPAM [RNA protospacer-adjacent motif]). The activated complex does not require a target sequence (or a PAM) in the DNA substrate. Plasmid elimination by the P. furiosus Cmr system also does not require the Csx1 (CRISPR-associated Rossman fold [CARF] superfamily) protein. Plasmid silencing depends on the HD nuclease and Palm domains of the Cmr2 (Cas10 superfamily) protein. The results establish the Cmr complex as a novel DNA nuclease activated by invader RNAs containing a crRNA target sequence and a rPAM.
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Date Issued: 2016-02-15
Identifier: FSU_pmch_26848045, 10.1101/gad.272153.115, PMC4762429, 26848045, 26848045, gad.272153.115
Format: Citation

Title: The sensitivity of fast muscle contractile function to the major components of the sarcomere Ca(2+)-cycling system.
Creator: Golding, C, Kelly, K, Kinsey, S T, Locke, B R
Abstract/Description: A reaction-diffusion model of a muscle sarcomere was developed to evaluate the sensitivity of force characteristics to diffusion and Ca(2+)-cycling components. The model compared well to experimental force measurements. Diffusion led to Ca(2+) gradients that enhanced maximal force and accelerated relaxation compared to when diffusion was infinitely fast. However, a modest increase in sarcomere length or radius led to a decrease in maximal force. Lowering the Ca(2+) release rate caused a lower...
Show moreA reaction-diffusion model of a muscle sarcomere was developed to evaluate the sensitivity of force characteristics to diffusion and Ca(2+)-cycling components. The model compared well to experimental force measurements. Diffusion led to Ca(2+) gradients that enhanced maximal force and accelerated relaxation compared to when diffusion was infinitely fast. However, a modest increase in sarcomere length or radius led to a decrease in maximal force. Lowering the Ca(2+) release rate caused a lower maximal force, but increasing the rate led to only modest gains in maximal force while incurring much greater ATP costs associated with reuptake. Greater parvalbumin binding rates decreased maximal force but enhanced relaxation, and this effect was magnified when Ca(2+) uptake rates were lowered as may occur during fatigue. These results show a physiological set of parameters that lead to a functional sarcomere of known dimensions and contractile function, and the effects of parameter variation on muscle function.
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Date Issued: 2016-04-01
Identifier: FSU_pmch_26774860, 10.1016/j.bpc.2016.01.001, PMC5003095, 26774860, 26774860, S0301-4622(15)30090-9
Format: Citation

Title: Predictive Sampling of Rare Conformational Events in Aqueous Solution: Designing a Generalized Orthogonal Space Tempering Method..
Creator: Lu, Chao, Li, Xubin, Wu, Dongsheng, Zheng, Lianqing, Yang, Wei
Abstract/Description: In aqueous solution, solute conformational transitions are governed by intimate interplays of the fluctuations of solute-solute, solute-water, and water-water interactions. To promote molecular fluctuations to enhance sampling of essential conformational changes, a common strategy is to construct an expanded Hamiltonian through a series of Hamiltonian perturbations and thereby broaden the distribution of certain interactions of focus. Due to a lack of active sampling of configuration response...
Show moreIn aqueous solution, solute conformational transitions are governed by intimate interplays of the fluctuations of solute-solute, solute-water, and water-water interactions. To promote molecular fluctuations to enhance sampling of essential conformational changes, a common strategy is to construct an expanded Hamiltonian through a series of Hamiltonian perturbations and thereby broaden the distribution of certain interactions of focus. Due to a lack of active sampling of configuration response to Hamiltonian transitions, it is challenging for common expanded Hamiltonian methods to robustly explore solvent mediated rare conformational events. The orthogonal space sampling (OSS) scheme, as exemplified by the orthogonal space random walk and orthogonal space tempering methods, provides a general framework for synchronous acceleration of slow configuration responses. To more effectively sample conformational transitions in aqueous solution, in this work, we devised a generalized orthogonal space tempering (gOST) algorithm. Specifically, in the Hamiltonian perturbation part, a solvent-accessible-surface-area-dependent term is introduced to implicitly perturb near-solute water-water fluctuations; more importantly in the orthogonal space response part, the generalized force order parameter is generalized as a two-dimension order parameter set, in which essential solute-solvent and solute-solute components are separately treated. The gOST algorithm is evaluated through a molecular dynamics simulation study on the explicitly solvated deca-alanine (Ala10) peptide. On the basis of a fully automated sampling protocol, the gOST simulation enabled repetitive folding and unfolding of the solvated peptide within a single continuous trajectory and allowed for detailed constructions of Ala10 folding/unfolding free energy surfaces. The gOST result reveals that solvent cooperative fluctuations play a pivotal role in Ala10 folding/unfolding transitions. In addition, our assessment analysis suggests that because essential conformational events are mainly driven by the compensating fluctuations of essential solute-solvent and solute-solute interactions, commonly employed "predictive" sampling methods are unlikely to be effective on this seemingly "simple" system. The gOST development presented in this paper illustrates how to employ the OSS scheme for physics-based sampling method designs.
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Date Issued: 2016-01-12
Identifier: FSU_pmch_26636477, 10.1021/acs.jctc.5b00953, PMC4968881, 26636477, 26636477
Format: Citation

Title: Free energy landscape of a minimalist salt bridge model.
Creator: Li, Xubin, Lv, Chao, Corbett, Karen M, Zheng, Lianqing, Wu, Dongsheng, Yang, Wei
Abstract/Description: Salt bridges are essential to protein stability and dynamics. Despite the importance, there has been scarce of detailed discussion on how salt bridge partners interact with each other in distinct solvent exposed environments. In this study, employing a recent generalized orthogonal space tempering (gOST) method, we enabled efficient molecular dynamics simulation of repetitive breaking and reforming of salt bridge structures within a minimalist salt-bridge model, the Asp-Arg dipeptide and...
Show moreSalt bridges are essential to protein stability and dynamics. Despite the importance, there has been scarce of detailed discussion on how salt bridge partners interact with each other in distinct solvent exposed environments. In this study, employing a recent generalized orthogonal space tempering (gOST) method, we enabled efficient molecular dynamics simulation of repetitive breaking and reforming of salt bridge structures within a minimalist salt-bridge model, the Asp-Arg dipeptide and thereby were able to map its detailed free energy landscape in aqueous solution. Free energy surface analysis shows that although individually-solvated states are more favorable, salt-bridge states still occupy a noticeable portion of the overall population. Notably, the competing forces, e.g. intercharge attractions that drive the formation of salt bridges and solvation forces that pull the charged groups away from each other, are energetically comparable. As the result, the salt bridge stability is highly tunable by local environments; for instance when local water molecules are perturbed to interact more strongly with each other, the population of the salt-bridge states is likely to increase. Our results reveal the critical role of local solvent structures in modulating salt-bridge partner interactions and imply the importance of water fluctuations on conformational dynamics that involves solvent accessible salt bridge formations.
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Date Issued: 2016-01-01
Identifier: FSU_pmch_26300526, 10.1002/pro.2789, PMC4815310, 26300526, 26300526
Format: Citation

Title: Interfacing Microfluidics with Negative Stain Transmission Electron Microscopy.
Creator: Mukhitov, Nikita, Spear, John M, Stagg, Scott M, Roper, Michael G
Abstract/Description: A microfluidic platform is presented for preparing negatively stained grids for use in transmission electron microscopy (EM). The microfluidic device is composed of glass etched with readily fabricated features that facilitate the extraction of the grid poststaining and maintains the integrity of the sample. Utilization of this device simultaneously reduced environmental contamination on the grids and improved the homogeneity of the heavy metal stain needed to enhance visualization of...
Show moreA microfluidic platform is presented for preparing negatively stained grids for use in transmission electron microscopy (EM). The microfluidic device is composed of glass etched with readily fabricated features that facilitate the extraction of the grid poststaining and maintains the integrity of the sample. Utilization of this device simultaneously reduced environmental contamination on the grids and improved the homogeneity of the heavy metal stain needed to enhance visualization of biological specimens as compared to conventionally prepared EM grids. This easy-to-use EM grid preparation device provides the basis for future developments of systems with more integrated features, which will allow for high-throughput and dynamic structural biology studies.
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Date Issued: 2016-01-05
Identifier: FSU_pmch_26642355, 10.1021/acs.analchem.5b03884, PMC4730115, 26642355, 26642355
Format: Citation

Title: DNA Interactions Probed by Hydrogen-Deuterium Exchange (HDX) Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Confirm External Binding Sites on the Minichromosomal Maintenance (MCM) Helicase.
Creator: Graham, Brian W, Tao, Yeqing, Dodge, Katie L, Thaxton, Carly T, Olaso, Danae, Young, Nicolas L, Marshall, Alan G, Trakselis, Michael A
Abstract/Description: The archaeal minichromosomal maintenance (MCM) helicase from Sulfolobus solfataricus (SsoMCM) is a model for understanding structural and mechanistic aspects of DNA unwinding. Although interactions of the encircled DNA strand within the central channel provide an accepted mode for translocation, interactions with the excluded strand on the exterior surface have mostly been ignored with regard to DNA unwinding. We have previously proposed an extension of the traditional steric exclusion model...
Show moreThe archaeal minichromosomal maintenance (MCM) helicase from Sulfolobus solfataricus (SsoMCM) is a model for understanding structural and mechanistic aspects of DNA unwinding. Although interactions of the encircled DNA strand within the central channel provide an accepted mode for translocation, interactions with the excluded strand on the exterior surface have mostly been ignored with regard to DNA unwinding. We have previously proposed an extension of the traditional steric exclusion model of unwinding to also include significant contributions with the excluded strand during unwinding, termed steric exclusion and wrapping (SEW). The SEW model hypothesizes that the displaced single strand tracks along paths on the exterior surface of hexameric helicases to protect single-stranded DNA (ssDNA) and stabilize the complex in a forward unwinding mode. Using hydrogen/deuterium exchange monitored by Fourier transform ion cyclotron resonance MS, we have probed the binding sites for ssDNA, using multiple substrates targeting both the encircled and excluded strand interactions. In each experiment, we have obtained >98.7% sequence coverage of SsoMCM from >650 peptides (5-30 residues in length) and are able to identify interacting residues on both the interior and exterior of SsoMCM. Based on identified contacts, positively charged residues within the external waist region were mutated and shown to generally lower DNA unwinding without negatively affecting the ATP hydrolysis. The combined data globally identify binding sites for ssDNA during SsoMCM unwinding as well as validating the importance of the SEW model for hexameric helicase unwinding.
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Date Issued: 2016-06-10
Identifier: FSU_pmch_27044751, 10.1074/jbc.M116.719591, PMC4933441, 27044751, 27044751, M116.719591
Format: Citation

Title: Structural Influences: Cholesterol, Drug, and Proton Binding to Full-Length Influenza A M2 Protein..
Creator: Ekanayake, E Vindana, Fu, Riqiang, Cross, Timothy A
Abstract/Description: The structure and functions of the M2 protein from Influenza A are sensitive to pH, cholesterol, and the antiinfluenza drug Amantadine. This is a tetrameric membrane protein of 97 amino-acid residues that has multiple functions, among them as a proton-selective channel and facilitator of viral budding, replacing the need for the ESCRT proteins that other viruses utilize. Here, various amino-acid-specific-labeled samples of the full-length protein were prepared and mixed, so that only...
Show moreThe structure and functions of the M2 protein from Influenza A are sensitive to pH, cholesterol, and the antiinfluenza drug Amantadine. This is a tetrameric membrane protein of 97 amino-acid residues that has multiple functions, among them as a proton-selective channel and facilitator of viral budding, replacing the need for the ESCRT proteins that other viruses utilize. Here, various amino-acid-specific-labeled samples of the full-length protein were prepared and mixed, so that only interresidue (13)C-(13)C cross peaks between two differently labeled proteins representing interhelical interactions are observed. This channel is activated at slightly acidic pH values in the endosome when the His(37) residues in the middle of the transmembrane domain take on a +2 or +3 charged state. Changes observed here in interhelical distances in the N-terminus can be accounted for by modest structural changes, and no significant changes in structure were detected in the C-terminal portion of the channel upon activation of the channel. Amantadine, which blocks proton conductance by binding in the aqueous pore near the N-terminus, however, significantly modifies the tetrameric structure on the opposite side of the membrane. The interactions between the juxtamembrane amphipathic helix of one monomer and its neighboring monomer observed in the absence of drug are disrupted in its presence. However, the addition of cholesterol prevents this structural disruption. In fact, strong interactions are observed between cholesterol and residues in the amphipathic helix, accounting for cholesterol binding adjacent to a native palmitoylation site and near to an interhelix crevice that is typical of cholesterol binding sites. The resultant stabilization of the amphipathic helix deep in the bilayer interface facilitates the bilayer curvature that is essential for viral budding.
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Date Issued: 2016-03-29
Identifier: FSU_pmch_27028648, 10.1016/j.bpj.2015.11.3529, PMC4816700, 27028648, 27028648, S0006-3495(16)00152-1
Format: Citation

Title: A Non-Stem-Loop CRISPR RNA Is Processed by Dual Binding Cas6.
Creator: Shao, Yaming, Richter, Hagen, Sun, Shengfang, Sharma, Kundan, Urlaub, Henning, Randau, Lennart, Li, Hong
Abstract/Description: A subclass of recently discovered CRISPR repeat RNA in bacteria contains minimally recognizable structural features that facilitate an unknown mechanism of recognition and processing by the Cas6 family of endoribonucleases. Cocrystal structures of Cas6 from Methanococcus maripaludis (MmCas6b) bound with its repeat RNA revealed a dual site binding structure and a cleavage site conformation poised for phosphodiester bond breakage. Two non-interacting MmCas6b bind to two separate AAYAA motifs...
Show moreA subclass of recently discovered CRISPR repeat RNA in bacteria contains minimally recognizable structural features that facilitate an unknown mechanism of recognition and processing by the Cas6 family of endoribonucleases. Cocrystal structures of Cas6 from Methanococcus maripaludis (MmCas6b) bound with its repeat RNA revealed a dual site binding structure and a cleavage site conformation poised for phosphodiester bond breakage. Two non-interacting MmCas6b bind to two separate AAYAA motifs within the same repeat, one distal and one adjacent to the cleavage site. This bound structure potentially competes with a stable but non-productive RNA structure. At the cleavage site, MmCas6b supplies a base pair mimic to stabilize a short 2 base pair stem immediately upstream of the scissile phosphate. Complementary biochemical analyses support the dual-AAYAA binding model and a critical role of the protein-RNA base pair mimic. Our results reveal a previously unknown method of processing non-stem-loop CRISPR RNA by Cas6.
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Date Issued: 2016-04-05
Identifier: FSU_pmch_26996962, 10.1016/j.str.2016.02.009, PMC4823167, 26996962, 26996962, S0969-2126(16)00068-X
Format: Citation

Title: Quantitative Mass Spectrometry Reveals Changes in Histone H2B Variants as Cells Undergo Inorganic Arsenic-Mediated Cellular Transformation.
Creator: Rea, Matthew, Jiang, Tingting, Eleazer, Rebekah, Eckstein, Meredith, Marshall, Alan G, Fondufe-Mittendorf, Yvonne N
Abstract/Description: Exposure to inorganic arsenic, a ubiquitous environmental toxic metalloid, leads to carcinogenesis. However, the mechanism is unknown. Several studies have shown that inorganic arsenic exposure alters specific gene expression patterns, possibly through alterations in chromatin structure. While most studies on understanding the mechanism of chromatin-mediated gene regulation have focused on histone post-translational modifications, the role of histone variants remains largely unknown....
Show moreExposure to inorganic arsenic, a ubiquitous environmental toxic metalloid, leads to carcinogenesis. However, the mechanism is unknown. Several studies have shown that inorganic arsenic exposure alters specific gene expression patterns, possibly through alterations in chromatin structure. While most studies on understanding the mechanism of chromatin-mediated gene regulation have focused on histone post-translational modifications, the role of histone variants remains largely unknown. Incorporation of histone variants alters the functional properties of chromatin. To understand the global dynamics of chromatin structure and function in arsenic-mediated carcinogenesis, analysis of the histone variants incorporated into the nucleosome and their covalent modifications is required. Here we report the first global mass spectrometric analysis of histone H2B variants as cells undergo arsenic-mediated epithelial to mesenchymal transition. We used electron capture dissociation-based top-down tandem mass spectrometry analysis validated with quantitative reverse transcription real-time polymerase chain reaction to identify changes in the expression levels of H2B variants in inorganic arsenic-mediated epithelial-mesenchymal transition. We identified changes in the expression levels of specific histone H2B variants in two cell types, which are dependent on dose and length of exposure of inorganic arsenic. In particular, we found increases in H2B variants H2B1H/1K/1C/1J/1O and H2B2E/2F, and significant decreases in H2B1N/1D/1B as cells undergo inorganic arsenic-mediated epithelial-mesenchymal transition. The analysis of these histone variants provides a first step toward an understanding of the functional significance of the diversity of histone structures, especially in inorganic arsenic-mediated gene expression and carcinogenesis.
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Date Issued: 2016-07-01
Identifier: FSU_pmch_27169413, 10.1074/mcp.M116.058412, PMC4937513, 27169413, 27169413, M116.058412
Format: Citation

Title: Noncompetitive affinity assays of glucagon and amylin using mirror-image aptamers as affinity probes.
Creator: Yi, Lian, Wang, Xue, Bethge, Lucas, Klussmann, Sven, Roper, Michael G
Abstract/Description: The ability to detect picomolar concentrations of glucagon and amylin using fluorescently labeled mirror-image aptamers, so-called Spiegelmers, is demonstrated. Spiegelmers rival the specificity of antibodies and overcome the problem of biostability of natural aptamers in a biological matrix. Using Spiegelmers as affinity probes, noncompetitive capillary electrophoresis affinity assays of glucagon and murine amylin were developed and optimized. The detection limit for glucagon was 6 pM and...
Show moreThe ability to detect picomolar concentrations of glucagon and amylin using fluorescently labeled mirror-image aptamers, so-called Spiegelmers, is demonstrated. Spiegelmers rival the specificity of antibodies and overcome the problem of biostability of natural aptamers in a biological matrix. Using Spiegelmers as affinity probes, noncompetitive capillary electrophoresis affinity assays of glucagon and murine amylin were developed and optimized. The detection limit for glucagon was 6 pM and for amylin was 40 pM. Glucagon-like peptide-1 and -2 did not interfere with the glucagon assay, while the amylin assay showed cross-reactivity to calcitonin gene related peptide. The developed assays were combined with a competitive immunoassay for insulin to measure glucagon, amylin, and insulin secretion from batches of islets after incubation with different glucose concentrations. The development of these assays is an important step towards incorporation into an online measurement system for monitoring dynamic secretion from single islets.
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Date Issued: 2016-03-21
Identifier: FSU_pmch_26881276, 10.1039/c5an02468d, PMC4783278, 26881276, 26881276
Format: Citation

Title: Genetic and cellular studies highlight that A Disintegrin and Metalloproteinase 19 is a protective biomarker in human prostate cancer.
Creator: Hoyne, Gerard, Rudnicka, Caroline, Sang, Qing-Xiang, Roycik, Mark, Howarth, Sarah, Leedman, Peter, Schlaich, Markus, Candy, Patrick, Matthews, Vance
Abstract/Description: Prostate cancer is the second most frequently diagnosed cancer in men worldwide. Current treatments include surgery, androgen ablation and radiation. Introduction of more targeted therapies in prostate cancer, based on a detailed knowledge of the signalling pathways, aims to reduce side effects, leading to better clinical outcomes for the patient. ADAM19 (A Disintegrin And Metalloproteinase 19) is a transmembrane and soluble protein which can regulate cell phenotype through cell adhesion and...
Show moreProstate cancer is the second most frequently diagnosed cancer in men worldwide. Current treatments include surgery, androgen ablation and radiation. Introduction of more targeted therapies in prostate cancer, based on a detailed knowledge of the signalling pathways, aims to reduce side effects, leading to better clinical outcomes for the patient. ADAM19 (A Disintegrin And Metalloproteinase 19) is a transmembrane and soluble protein which can regulate cell phenotype through cell adhesion and proteolysis. ADAM19 has been positively associated with numerous diseases, but has not been shown to be a tumor suppressor in the pathogenesis of any human cancers. Our group sought to investigate the role of ADAM19 in human prostate cancer. ADAM19 mRNA and protein levels were assessed in well characterised human prostate cancer cohorts. ADAM19 expression was assessed in normal prostate epithelial cells (RWPE-1) and prostate cancer cells (LNCaP, PC3) using western blotting and immunocytochemistry. Proliferation assays were conducted in LNCaP cells in which ADAM19 was over-expressed. In vitro scratch assays were performed in PC3 cells over-expressing ADAM19. Immunohistochemical studies highlighted that ADAM19 protein levels were elevated in normal prostate tissue compared to prostate cancer biopsies. Results from the clinical cohorts demonstrated that high levels of ADAM19 in microarrays are positively associated with lower stage (p = 0.02591) and reduced relapse (p = 0.00277) of human prostate cancer. In vitro, ADAM19 expression was higher in RWPE-1 cells compared to LNCaP cells. In addition, human ADAM19 over-expression reduced LNCaP cell proliferation and PC3 cell migration. Taken together, our immunohistochemical and microarray results and cellular studies have shown for the first time that ADAM19 is a protective factor for human prostate cancer. Further, this study suggests that upregulation of ADAM19 expression could be of therapeutic potential in human prostate cancer.
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Date Issued: 2016-02-24
Identifier: FSU_pmch_26912236, 10.1186/s12885-016-2178-4, PMC4766641, 26912236, 26912236, 10.1186/s12885-016-2178-4
Format: Citation

Title: Wnt-YAP interactions in the neural fate of human pluripotent stem cells and the implications for neural organoid formation.
Creator: Bejoy, Julie, Song, Liqing, Li, Yan
Abstract/Description: Human pluripotent stem cells (hPSCs) have shown the ability to self-organize into different types of neural organoids (e.g., whole brain organoids, cortical spheroids, midbrain organoids etc.) recently. The extrinsic and intrinsic signaling elicited by Wnt pathway, Hippo/Yes-associated protein (YAP) pathway, and extracellular microenvironment plays a critical role in brain tissue morphogenesis. This article highlights recent advances in neural tissue patterning from hPSCs, in particular the...
Show moreHuman pluripotent stem cells (hPSCs) have shown the ability to self-organize into different types of neural organoids (e.g., whole brain organoids, cortical spheroids, midbrain organoids etc.) recently. The extrinsic and intrinsic signaling elicited by Wnt pathway, Hippo/Yes-associated protein (YAP) pathway, and extracellular microenvironment plays a critical role in brain tissue morphogenesis. This article highlights recent advances in neural tissue patterning from hPSCs, in particular the role of Wnt pathway and YAP activity in this process. Understanding the Wnt-YAP interactions should provide us the guidance to predict and modulate brain-like tissue structure through the regulation of extracellular microenvironment of hPSCs.
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Date Issued: 2016-01-02
Identifier: FSU_pmch_26901039, 10.1080/15476278.2016.1140290, PMC4882124, 26901039, 26901039
Format: Citation

Title: Distinguishing Förster resonance energy transfer and solvent-mediated charge-transfer relaxation dynamics in a zinc(II) indicator: a femtosecond time-resolved transient absorption spectroscopic study.
Creator: Zhu, Lei, Sreenath, Kesavapillai, Yi, Chongyue, Knappenberger, Kenneth
Abstract/Description: A bifluorophoric molecule (1) capable of intramolecular Förster Resonance Energy Transfer (FRET) is reported. The emission intensity of the FRET acceptor in 1 depends on the molar absorptivity of the donor, which is a function of zinc(II) complexation. The FRET dynamics of [Zn(1)](ClO4)2 is characterized by femtosecond time-resolved transient absorption spectroscopy. The solvent-mediated relaxation of the charge-transfer (CT) state of the isolated donor and the FRET process of the donor...
Show moreA bifluorophoric molecule (1) capable of intramolecular Förster Resonance Energy Transfer (FRET) is reported. The emission intensity of the FRET acceptor in 1 depends on the molar absorptivity of the donor, which is a function of zinc(II) complexation. The FRET dynamics of [Zn(1)](ClO4)2 is characterized by femtosecond time-resolved transient absorption spectroscopy. The solvent-mediated relaxation of the charge-transfer (CT) state of the isolated donor and the FRET process of the donor–acceptor conjugate are on similar time scales (40–50 ps in CH3CN), but distinguishable by the opposite solvent polarity dependency. As the solvent polarity increases, the efficiency of Columbic-based FRET is reduced, whereas CT relaxation is accelerated. In addition to revealing a method to distinguish CT and FRET dynamics, this work provides a photophysical foundation for developing indicators based on the FRET strategy.
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Date Issued: 2014
Identifier: FSU_migr_chm_faculty_publications-0015, 10.1039/C3CP55382E
Format: Citation

Title: Competing Covalent And Ionic Bonding In Ge-sb-te Phase Change Materials.
Creator: Mukhopadhyay, Saikat, Sun, Jifeng, Subedi, Alaska, Siegrist, Theo, Singh, David J.
Abstract/Description: Ge2Sb2Te5 and related phase change materials are highly unusual in that they can be readily transformed between amorphous and crystalline states using very fast melt, quench, anneal cycles, although the resulting states are extremely long lived at ambient temperature. These states have remarkably different physical properties including very different optical constants in the visible in strong contrast to common glass formers such as silicates or phosphates. This behavior has been described in...
Show moreGe2Sb2Te5 and related phase change materials are highly unusual in that they can be readily transformed between amorphous and crystalline states using very fast melt, quench, anneal cycles, although the resulting states are extremely long lived at ambient temperature. These states have remarkably different physical properties including very different optical constants in the visible in strong contrast to common glass formers such as silicates or phosphates. This behavior has been described in terms of resonant bonding, but puzzles remain, particularly regarding different physical properties of crystalline and amorphous phases. Here we show that there is a strong competition between ionic and covalent bonding in cubic phase providing a link between the chemical basis of phase change memory property and origins of giant responses of piezoelectric materials (PbTi3, BiFeO3). This has important consequences for dynamical behavior in particular leading to a simultaneous hardening of acoustic modes and softening of high frequency optic modes in crystalline phase relative to amorphous. This different bonding in amorphous and crystalline phases provides a direct explanation for different physical properties and understanding of the combination of long time stability and rapid switching and may be useful in finding new phase change compositions with superior properties.
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Date Issued: 2016-05-19
Identifier: FSU_libsubv1_wos_000376374200001, 10.1038/srep25981
Format: Citation

Title: Correlation of Seebeck Coefficient and Electric Conductivity in Polyaniline and Polypyrrole.
Creator: Mateeva, N., Niculescu, H., Schlenoff, Joseph B., Testardi, L.
Abstract/Description: We have measured the Seebeck coefficient and electric conductivity in the air-stable conducting polymers polyaniline and polypyrrole at different doping levels. We find, at 300 K, the general correlation that the logarithm of the electrical conductivity varies linearly with the Seebeck coefficient on doping, but with a proportionality substantially in excess of a prediction from simple theory for a single type of mobile carrier. The correlation is unexpected in its universality and...
Show moreWe have measured the Seebeck coefficient and electric conductivity in the air-stable conducting polymers polyaniline and polypyrrole at different doping levels. We find, at 300 K, the general correlation that the logarithm of the electrical conductivity varies linearly with the Seebeck coefficient on doping, but with a proportionality substantially in excess of a prediction from simple theory for a single type of mobile carrier. The correlation is unexpected in its universality and unfavorable in its consequences for thermoelectric applications. A standard model suggests that conduction by carriers of both signs may occur in these doped polymers, which thus leads to reduced thermoelectric efficiency. We also show that polyacetylene ~which is not air stable!, does exhibit the correlation with the expected proportionality, and, thus, its properties could be more favorable for thermoelectricity. © 1998 American Institute of Physics. [S0021-8979(98)05906-4]
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Date Issued: 1998
Identifier: FSU_migr_chm_faculty_publications-0001, 10.1063/1.367119
Format: Citation

Title: Corrosion Control Using Polyelectrolyte Multilayers.
Creator: Farhat, Tarek, Schlenoff, Joseph B.
Abstract/Description: The corrosion of stainless steel under anodic conditions in salt solutions was strongly suppressed by an ultrathin layer of polyelectrolyte complex, applied using the layer-by-layer deposition method. Voltammetric scans over a wide potential region, as well as constant potential measurements in the metastable pitting regime, reveal the surprising effectiveness of polyelectrolyte multilayers, both hydrophilic and hydrophobic, at corrosion control, despite the significant water content and ion...
Show moreThe corrosion of stainless steel under anodic conditions in salt solutions was strongly suppressed by an ultrathin layer of polyelectrolyte complex, applied using the layer-by-layer deposition method. Voltammetric scans over a wide potential region, as well as constant potential measurements in the metastable pitting regime, reveal the surprising effectiveness of polyelectrolyte multilayers, both hydrophilic and hydrophobic, at corrosion control, despite the significant water content and ion permeability of the thin film.
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Date Issued: 2002
Identifier: FSU_migr_chm_faculty_publications-0010, 10.1149/1.1452484
Format: Citation

Title: Design Principles for High H2 Storage Using Chelation of Abundant Transition Metals in Covalent Organic Frameworks for 0-700 bar at 298K.
Creator: Mendoza-Cortes, Jose, Pramudya, Yohanes
Abstract/Description: Physisorption is an effective route to meet hydrogen gas (H2) storage and delivery requirements for transportation because it is fast and fully reversible under mild conditions. However, most current candidates have too small binding enthalpies to H2 which leads to volumetric capacity less than 10 g/L compared to that of the system target of 40 g/L at 298 K. Accurate quantum mechanical (QM) methods were used to determine the H2 binding enthalpy of 5 linkers which were chelated with 11...
Show morePhysisorption is an effective route to meet hydrogen gas (H2) storage and delivery requirements for transportation because it is fast and fully reversible under mild conditions. However, most current candidates have too small binding enthalpies to H2 which leads to volumetric capacity less than 10 g/L compared to that of the system target of 40 g/L at 298 K. Accurate quantum mechanical (QM) methods were used to determine the H2 binding enthalpy of 5 linkers which were chelated with 11 different transition metals (Tm), including abundant first-row Tm (Sc through Cu), totaling 60 molecular compounds with more than 4 configurations related to the different number of H2 that interact with the molecular compound. It was found that first-row Tm gave similar and sometimes superior van der Waals interactions with H2 than precious Tm. Based on these linkers, 30 new covalent organic frameworks (COFs) were constructed. The H2 uptakes of these new COFs were determined using quantum mechanics (QM)-based force fields and grand canonical Monte Carlo (GCMC) simulations. For the first time, the range for the adsorption pressure was explored for 0–700 bar and 298 K. It was determined that Co-, Ni-, and Fe-based COFs can give high H2 uptake and delivery when compared to bulk H2 on this unexplored range of pressure.
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Date Issued: 2016-10-28
Identifier: FSU_libsubv1_scholarship_submission_1481210857, 10.1021/jacs.6b08803
Format: Citation

Title: DNA Interactions Probed by Hydrogen-Deuterium Exchang (HDX) Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Confirm External Binding Sites on the Minichromosomal Maintenance (MCM) Helicase.
Creator: Graham, Brian W., Tao, Yeqing, Dodge, Katie L., Thaxton, Carly T., Olaso, Danae, Young, Nicolas L., Marshall, Alan G., Trakselis, Michael A.
Abstract/Description: The archaeal minichromosomal maintenance (MCM) helicase from Sulfolobus solfataricus (SsoMCM) is a model for understanding structural and mechanistic aspects of DNA unwinding. Although interactions of the encircled DNA strand within the central channel provide an accepted mode for translocation, interactions with the excluded strand on the exterior surface have mostly been ignored with regard to DNA unwinding. We have previously proposed an extension of the traditional steric exclusion model...
Show moreThe archaeal minichromosomal maintenance (MCM) helicase from Sulfolobus solfataricus (SsoMCM) is a model for understanding structural and mechanistic aspects of DNA unwinding. Although interactions of the encircled DNA strand within the central channel provide an accepted mode for translocation, interactions with the excluded strand on the exterior surface have mostly been ignored with regard to DNA unwinding. We have previously proposed an extension of the traditional steric exclusion model of unwinding to also include significant contributions with the excluded strand during unwinding, termed steric exclusion and wrapping (SEW). The SEW model hypothesizes that the displaced single strand tracks along paths on the exterior surface of hexameric helicases to protect single-stranded DNA (ssDNA) and stabilize the complex in a forward unwinding mode. Using hydrogen/deuterium exchange monitored by Fourier transform ion cyclotron resonance MS, we have probed the binding sites for ssDNA, using multiple substrates targeting both the encircled and excluded strand interactions. In each experiment, we have obtained >98.7% sequence coverage of SsoMCM from >650 peptides (5-30 residues in length) and are able to identify interacting residues on both the interior and exterior of SsoMCM. Based on identified contacts, positively charged residues within the external waist region were mutated and shown to generally lower DNA unwinding without negatively affecting the ATP hydrolysis. The combined data globally identify binding sites for ssDNA during SsoMCM unwinding as well as validating the importance of the SEW model for hexameric helicase unwinding.
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Date Issued: 2016-06-10
Identifier: FSU_libsubv1_wos_000378119900003, 10.1074/jbc.M116.719591
Format: Citation

Title: The Cyclic Voltammetry of Pristine, Isomerized, Deuterated, and Partially Hydrogenated "P-Type" Polyacetylene.
Creator: Schlenoff, Joseph B., Chien, James C. W.
Abstract/Description: The cyclic voltammetry of ultrathin fihns of polyacetylene comprised of 2-3 nm micro fibrils and their aggregate 20 nm fibrils in methylene chloride, acetonitrile, propylene carbonate, and sulfo]ane shows many similarities, including a background oxidation of electrolyte that leads to serious coulombic inefficiency in rechargeable polyacetylene battery applications. Reversible charging in neutral aqueous solution is limited by the poor separation between the reversible and irreversible...
Show moreThe cyclic voltammetry of ultrathin fihns of polyacetylene comprised of 2-3 nm micro fibrils and their aggregate 20 nm fibrils in methylene chloride, acetonitrile, propylene carbonate, and sulfo]ane shows many similarities, including a background oxidation of electrolyte that leads to serious coulombic inefficiency in rechargeable polyacetylene battery applications. Reversible charging in neutral aqueous solution is limited by the poor separation between the reversible and irreversible oxidations. Comparison of ultrathin and free-standing 100 ~m thick films showed they have the same maximum reversible doping level and thus energy density of 280 Wh/kg. Pristine, isomerized, deuterated, and hydrogenated [CH].,. show similar electrochemistry. Both n and p-type chemical doping caused isomerization of cis-[CHL to trans-[CH]~.
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Date Issued: 1987
Identifier: FSU_migr_chm_faculty_publications-0007, 10.1149/1.2100848
Format: Citation

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