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Articles 1 - 30 of 89
Full-Text Articles in Physical Sciences and Mathematics
Prediction And Confirmation Of A Switch-Like Region Within The N-Terminal Domain Of Hsirt1, Angelina T. Huynh, Thi-Tina N. Nguyen, Carina A. Villegas, Saira Montemorso, Benjamin Strauss, Richard A. Pearson, Jason G. Graham, Jonathan Oribello, Rohit Suresh, Brooke Lustig, Ningkun Wang
Prediction And Confirmation Of A Switch-Like Region Within The N-Terminal Domain Of Hsirt1, Angelina T. Huynh, Thi-Tina N. Nguyen, Carina A. Villegas, Saira Montemorso, Benjamin Strauss, Richard A. Pearson, Jason G. Graham, Jonathan Oribello, Rohit Suresh, Brooke Lustig, Ningkun Wang
Faculty Research, Scholarly, and Creative Activity
Many proteins display conformational changes resulting from allosteric regulation. Often only a few residues are crucial in conveying these structural and functional allosteric changes. These regions that undergo a significant change in structure upon receiving an input signal, such as molecular recognition, are defined as switch- like regions. Identifying these key residues within switch-like regions can help elucidate the mechanism of allosteric regulation and provide guidance for synthetic regulation. In this study, we combine a novel computational workflow with biochemical methods to identify a switch-like region in the N-terminal domain of human SIRT1 (hSIRT1), a lysine deacetylase that plays important …
Statistical Potentials For Rna-Protein Interactions Optimized By Cma-Es, Takayuki Kimura, Nobuaki Yasuo, Masakazu Sekijima, Brooke Lustig
Statistical Potentials For Rna-Protein Interactions Optimized By Cma-Es, Takayuki Kimura, Nobuaki Yasuo, Masakazu Sekijima, Brooke Lustig
Faculty Research, Scholarly, and Creative Activity
Characterizing RNA-protein interactions remains an important endeavor, complicated by the difficulty in obtaining the relevant structures. Evaluating model structures via statistical potentials is in principle straight-forward and effective. However, given the relatively small size of the existing learning set of RNA-protein complexes optimization of such potentials continues to be problematic. Notably, interaction-based statistical potentials have problems in addressing large RNA-protein complexes. In this study, we adopted a novel strategy with covariance matrix adaptation (CMA-ES) to calculate statistical potentials, successfully identifying native docking poses.
Ru(Ii)-Diimine Complexes And Cytochrome P450 Working Hand-In-Hand, Celine Eidenschenk, Lionel Cheruzel
Ru(Ii)-Diimine Complexes And Cytochrome P450 Working Hand-In-Hand, Celine Eidenschenk, Lionel Cheruzel
Faculty Publications, Chemistry
With a growing interest in utilizing visible light to drive biocatalytic processes, several light-harvesting units and approaches have been employed to harness the synthetic potential of heme monooxygenases and carry out selective oxyfunctionalization of a wide range of substrates. While the fields of cytochrome P450 and Ru(II) photochemistry have separately been prolific, it is not until the turn of the 21st century that they converged. Non-covalent and subsequently covalently attached Ru(II) complexes were used to promote rapid intramolecular electron transfer in bacterial P450 enzymes. Photocatalytic activity with Ru(II)-modified P450 enzymes was achieved under reductive conditions with a judicious choice of …
The Development Of Silica Hydride Stationary Phases For High-Performance Liquid Chromatography From Conception To Commercialization, Maria Matyska-Pesek, Joseph Pesek
The Development Of Silica Hydride Stationary Phases For High-Performance Liquid Chromatography From Conception To Commercialization, Maria Matyska-Pesek, Joseph Pesek
Faculty Publications, Chemistry
The development of a stationary phase material for high-performance liquid chromatography based on a surface of silica hydride as opposed to silanols on ordinary silica is discussed including synthetic approaches, characterization, and applications. There are several synthetic approaches available to create a silica hydride surface. Modification of the Si–H moiety on the silica surface can be accomplished through the use of a hydrosilation reaction. Both the intermediate silica hydride and the material modified with an organic moiety can be characterized by a number of spectroscopic as well as a variety of other methods. Further insights into the retention mechanism are …
The Importance Of Solvent Effects On The Mechanism Of The Pfeiffer Effect, Jamie Lunkley, Ngoc Nguyen, Kristina Tuminaro, Dana Margittai, Gilles Muller
The Importance Of Solvent Effects On The Mechanism Of The Pfeiffer Effect, Jamie Lunkley, Ngoc Nguyen, Kristina Tuminaro, Dana Margittai, Gilles Muller
Faculty Publications, Chemistry
The Pfeiffer effect is observed when an optically active compound such as an amino acid is introduced to a solution containing a labile racemic metal complex, and an equilibrium shift is obtained. The “perturbation” results in an excess of one enantiomer over the other. The shift is a result of a preferential outer sphere interaction between the introduced chiral species and one enantiomeric form (Λ or ∆) of a labile metal complex. Speculations regarding the mechanism of the Pfeiffer effect have attributed observations to a singular factor such as pH, solvent polarity, or numerous other intermolecular interactions. Through the use …
Superconductivity At Т≈200 K In Bismuth Cuprates Synthesized Using Solar Energy, J. Chigvinadze, Juana Acrivos, S. Ashimov, D. Gulamova, G. Donadze
Superconductivity At Т≈200 K In Bismuth Cuprates Synthesized Using Solar Energy, J. Chigvinadze, Juana Acrivos, S. Ashimov, D. Gulamova, G. Donadze
Faculty Publications, Chemistry
When investigating low-frequency (0.1 Hz) oscillations of multiphase high-temperature cuprate superconductors (HTCS) Bi1,7Pb0,3Sr2Ca(n-1)CunOy (n=2-30), a wide attenuation peak (ΔT~100 К) with a maximum at Т≈200 К was detected. This peak was particularly pronounced in field cooling (FC) experiments, i.e. after abrupt cooling of the sample in the external magnetic field at the temperature Т<Тс with subsequent slow warming up to room temperature with invariance of the applied field. The attenuation peak height depended on the preliminaryorientation (before cooling) of the samples θ in the measured permanent magnetic field Н. On the one hand, it is well known that, after the FC procedure and subsequent slow warming up, at the temperatures close to the critical temperature Тс, the attenuation peak associated with “melting” of the Abrikosov frozen vortex structure and its disappearance at Т >Тс is detected in monophase samples. At the same time, in most multiphase bismuth HTCS samples, synthesized using solar energy and superfast quenching of the melt, the attenuation peak with the maximum at Т≈200 К was observed.Depending on the conditions of synthesis, the attenuation peak could …
Spin-Imbalance In A 2d Fermi-Hubbard System, Peter Brown, Debayan Mitra, Elmer Guardado-Sanchez, Peter Schauß, Stanimir Kondov, Ehsan Khatami, Thereza Paiva, Nandini Trivedi, David Huse, Waseem Bakr
Spin-Imbalance In A 2d Fermi-Hubbard System, Peter Brown, Debayan Mitra, Elmer Guardado-Sanchez, Peter Schauß, Stanimir Kondov, Ehsan Khatami, Thereza Paiva, Nandini Trivedi, David Huse, Waseem Bakr
Faculty Publications
The interplay of strong interactions and magnetic fields gives rise to unusual forms of superconductivity and magnetism in quantum many-body systems. Here, we present an experimental study of the two-dimensional Fermi-Hubbard model—a paradigm for strongly correlated fermions on a lattice—in the presence of a Zeeman field and varying doping. Using site-resolved measurements, we revealed anisotropic antiferromagnetic correlations, a precursor to long-range canted order. We observed nonmonotonic behavior of the local polarization with doping for strong interactions, which we attribute to the evolution from an antiferromagnetic insulator to a metallic phase. Our results pave the way to experimentally mapping the low-temperature …
Abca' Tetrablock Terpolymers: Synthesis And Morphology, Madalyn Radlauer, Seijiro Fukuta, Megan Matta, Joshua Van Benschoten, Marc Hillmyer
Abca' Tetrablock Terpolymers: Synthesis And Morphology, Madalyn Radlauer, Seijiro Fukuta, Megan Matta, Joshua Van Benschoten, Marc Hillmyer
Faculty Publications, Chemistry
No abstract provided.
Proximal Effects In Bimetallic Catalysts For Olefin Polymerization, In Cross Metathesis Of Poly(3-R-Cyclooctenes), And In Multiblock Polymers, Madalyn Radlauer, Theodor Agapie, Marc Hillmyer
Proximal Effects In Bimetallic Catalysts For Olefin Polymerization, In Cross Metathesis Of Poly(3-R-Cyclooctenes), And In Multiblock Polymers, Madalyn Radlauer, Theodor Agapie, Marc Hillmyer
Faculty Publications, Chemistry
Proximity and sterics play a large role in polymerization and polymer chemistry. In the development and testing of bimetallic polymerization catalysts where the two metal centers are held on the same side of the molecule by a rigid ligand framework, the proximity of the second metal changes reactivity at the first. The resulting enhancements of polar group tolerance or isoselecitivity in olefin polymerization are not observed in related bimetallic systems with distal metal centers or in monometallic analogues. In cross metathesis between poly(cyclooctene) chains, high E-stereoregularity and head-to-tail regioregularity are achieved with Grubbs second or third generation catalysts when there …
Conformational Changes And Chiroptical Switching Of Enantiopure Bis-Helicenic Terpyridine Upon Zn2+ Binding, Helena Isla, Monika Srebro-Hooper, Marion Jean, Nicolas Vanthuyne, Thierry Roisnel, Jamie Lunkley, Gilles Muller, J. Gareth-Williams, Jochen Autschbach, Jeanne Crassous
Conformational Changes And Chiroptical Switching Of Enantiopure Bis-Helicenic Terpyridine Upon Zn2+ Binding, Helena Isla, Monika Srebro-Hooper, Marion Jean, Nicolas Vanthuyne, Thierry Roisnel, Jamie Lunkley, Gilles Muller, J. Gareth-Williams, Jochen Autschbach, Jeanne Crassous
Faculty Publications, Chemistry
The molecular conformation of a bis-helicenic terpyridine system is strongly modified upon binding to Zn(II) ion, a process that is accompanied by large changes in the optical and chiroptical properties. This system affords a new type of helicene-based chiroptical switching.
Functionalized Cationic [4]Helicenes With Unique Tuning Of Absorption, Fluorescence And Chiroptical Properties Up To The Far-Red Range, I. Hernández Delgado, S. Pascal, A. Wallabregue, R. Duwald, C. Besnard, L. Guénée, C. Nançoz, E. Vauthey, R. Tovar, J. Lunkley, Gilles Muller, J. Lacour
Functionalized Cationic [4]Helicenes With Unique Tuning Of Absorption, Fluorescence And Chiroptical Properties Up To The Far-Red Range, I. Hernández Delgado, S. Pascal, A. Wallabregue, R. Duwald, C. Besnard, L. Guénée, C. Nançoz, E. Vauthey, R. Tovar, J. Lunkley, Gilles Muller, J. Lacour
Faculty Publications, Chemistry
Unprecedented regioselective post-functionalization of racemic and enantiopure cationic diaza [4]helicenes is afforded. The peripheral auxochrome substituents allow a general tuning of the electrochemical, photophysical and chiroptical properties of the helical dyes (26 examples). For instance, electronic absorption and circular dichroism are modulated from the orange to near-infrared spectral range (575–750 nm), fluorescence quantum efficiency is enhanced up to 0.55 (631 nm) and circularly polarized luminescence is recorded in the red (|glum| ∼ 10−3).
Logistic Regression Models To Predict Solvent Accessible Residues Using Sequence- And Homology-Based Qualitative And Quantitative Descriptors Applied To A Domain-Complete X-Ray Structure Learning Set, Reecha Nepal, Joanna Spencer, Guneet Bhogal, Amulya Nedunuri, Thomas Poelman, Thejas Kamath, Edwin Chung, Katherine Kantardjieff, Andrea Gottlieb, Brooke Lustig
Logistic Regression Models To Predict Solvent Accessible Residues Using Sequence- And Homology-Based Qualitative And Quantitative Descriptors Applied To A Domain-Complete X-Ray Structure Learning Set, Reecha Nepal, Joanna Spencer, Guneet Bhogal, Amulya Nedunuri, Thomas Poelman, Thejas Kamath, Edwin Chung, Katherine Kantardjieff, Andrea Gottlieb, Brooke Lustig
Faculty Publications, Chemistry
A working example of relative solvent accessibility (RSA) prediction for proteins is presented. Novel logistic regression models with various qualitative descriptors that include amino acid type and quantitative descriptors that include 20- and six-term sequence entropy have been built and validated. A domain-complete learning set of over 1300 proteins is used to fit initial models with various sequence homology descriptors as well as query residue qualitative descriptors. Homology descriptors are derived from BLASTp sequence alignments, whereas the RSA values are determined directly from the crystal structure. The logistic regression models are fitted using dichotomous responses indicating buried or accessible solvent, …
Frustrated Abc Triblock Terpolymers Morphologies, Madalyn Radlauer, Yusuke Asai, Christophe Sinturel, Marc Hillmyer
Frustrated Abc Triblock Terpolymers Morphologies, Madalyn Radlauer, Yusuke Asai, Christophe Sinturel, Marc Hillmyer
Faculty Publications, Chemistry
No abstract provided.
Potential Switchable Circularly Polarized Luminescence From Chiral Cyclometalated Platinum(Ii) Complexes, Xiao-Peng Zhang Zhang, Victoria Chang, Jian Liu, Xiao-Liang Yang, Wei Huan, Yizhi Li, Cheng-Hui Li, Gilles Muller, Xiao-Zeng You
Potential Switchable Circularly Polarized Luminescence From Chiral Cyclometalated Platinum(Ii) Complexes, Xiao-Peng Zhang Zhang, Victoria Chang, Jian Liu, Xiao-Liang Yang, Wei Huan, Yizhi Li, Cheng-Hui Li, Gilles Muller, Xiao-Zeng You
Faculty Publications, Chemistry
A series of chiral cyclometalated platinum(II) complexes, [Pt((−)-L1)(Dmpi)]Cl ((−)-1), [Pt((+)-L1)(Dmpi)]Cl ((+)-1), [Pt((−)-L2)(Dmpi)]Cl ((−)-2), [Pt((+)-L2)(Dmpi)]Cl ((+)-2), [Pt3((−)-L2)2(Dmpi)4](ClO4)4 ((−)-3), and [Pt3((+)-L2)2(Dmpi)4](ClO4)4 ((+)-3) [(−)-L1 = (−)-4,5-pinene-6′-phenyl-2,2′-bipyridine, (+)-L1 = (+)-4,5-pinene-6′-phenyl-2,2′-bipyridine), (−)-L2 = (−)-1,3-bis(2-(4,5-pinene)pyridyl)benzene, (+)-L2 = (+)-1,3-bis(2-(4,5-pinene)pyridyl)benzene, Dmpi = 2,6-dimethylphenyl isocyanide], have been designed and synthesized. In aqueous solutions, (−)-1 and (+)-1 aggregate into one-dimensional helical chain structures through Pt···Pt, π–π, and hydrophobic–hydrophobic interactions. (−)-3 and (+)-3 represent a novel helical structure with Pt–Pt bonds. The formation of helical structures results in enhanced and distinct chiroptical properties as evidenced by circular dichroism spectra. Circularly polarized luminescence (CPL) was observed from the aggregates of (−)-1 and …
Enantio-Enriched Cpl-Active Helicene–Bipyridine–Rhenium Complexes, Nidal Saleh, Monika Srebro, Thibault Reynaldo, Nicolas Vanthuyne, Loïc Toupet, Victoria Chang, Gilles Muller, J. Gareth-Williams, Christian Roussel, Jochen Autschbach, Jeanne Crassous
Enantio-Enriched Cpl-Active Helicene–Bipyridine–Rhenium Complexes, Nidal Saleh, Monika Srebro, Thibault Reynaldo, Nicolas Vanthuyne, Loïc Toupet, Victoria Chang, Gilles Muller, J. Gareth-Williams, Christian Roussel, Jochen Autschbach, Jeanne Crassous
Faculty Publications, Chemistry
The incorporation of a rhenium atom within an extended helical π-conjugated bi-pyridine system impacts the chiroptical and photophysical properties of the resulting neutral or cationic complexes, leading to the first examples of rhenium-based phosphors that exhibit circularly polarized luminescence.
Fast Melt Cooled Superconducting Alloys: (Bi1.97pb0.03sr2can‐1cuno2n+4+Δ)2 N/N’ N<24 Intergrowth, J. Kmiec, Juana Acrivos, D. Gulamova, J. Chigvinadze
Fast Melt Cooled Superconducting Alloys: (Bi1.97pb0.03sr2can‐1cuno2n+4+Δ)2 N/N’ N<24 Intergrowth, J. Kmiec, Juana Acrivos, D. Gulamova, J. Chigvinadze
Faculty Publications, Chemistry
High temperature layer superconducting cuprate (HTLSC) alloys: (Bi1.97Pb0.03Sr2Can-1CunO2n+4+δ)2 called (2s:2:n-1:n) have been grown from n-oxide stoichiometric melts in concentrated sun flux, followed by rapid cooling SFQA technology that preserves the melt tiling after annealing at 845±5oC**. Synchrotron XRD at the DOE SLAC-SSRL near the Cu K-edge has identified the mixing of n ≠ n’ alloys as observed by many in thin films last century. An ideal D17 4h Space Group structure obtains {an, bn, cn} = {3.815 Å, an+ubn, 2dP(n+3)+ucn} where dP is a perovskite sandwich, (CuO2)1/2|_Ca|(CuO2)1/2, thickness, and un are the amplitudes of periodic lattice distortions, PLD also observed …
Résonance Dans Alliages Des Couches Supraconductrices Refroidi Rapidement: (Bi1.7pb0.3sr2can‐1cuno2n+4+Δ)2, N=1 To 9détecté Par Local Renforcée Atomique Xrd, Juana Acrivos, J. Chigvinadze, D. Gulamova
Résonance Dans Alliages Des Couches Supraconductrices Refroidi Rapidement: (Bi1.7pb0.3sr2can‐1cuno2n+4+Δ)2, N=1 To 9détecté Par Local Renforcée Atomique Xrd, Juana Acrivos, J. Chigvinadze, D. Gulamova
Faculty Publications, Chemistry
Lien résonance dans alliages supraconductrice à haute température (HTLSC): (Bi1.7Pb0.3Sr2Can-1CunO2n+4+δ)2,n=1-9 appelé (2s:2:n-1:n) préparé en Ouzbékistan à partir de oxide fondu par flux concentré du Soleil, suivi d'un refroidissement rapide, technologie SFQA préserve fondre carrelage. Tc,n est mesurée en Tbilissi, et atomique local renforcée synchrotron diffraction des rayons X, (XRD) à proximité de la Cu-K bord est effectuée à DOE National Laboratoire SLAC-SSRL. La structure indexé dans le groupe D17 4h démontre qui (n-1) unîtes: (CuO2)1/2/Ca/(CuO2)1/2 sont intercalés à chaque extrémité de la phase n=1: [(CuO2)1/2/SrO/Bi1.7Pb0.3O/Bi1.7Pb0.3O/SrO/(CuO2)1/2]2. Les effets de surface conduit à intercalations des different n-phase, et à des distorsions réseau …
Covalent Bonds In Superconducting Rapid Cooled Alloys: (Bi1.7pb0.3sr2can‐1cuno2n+4+Δ)2, N=1 To 9 Detected By Local Atomic Enhanced Xrd, J. Kmiec, K. Tyson, Juana Acrivos, D. Gulamova, J. Chigvinadze
Covalent Bonds In Superconducting Rapid Cooled Alloys: (Bi1.7pb0.3sr2can‐1cuno2n+4+Δ)2, N=1 To 9 Detected By Local Atomic Enhanced Xrd, J. Kmiec, K. Tyson, Juana Acrivos, D. Gulamova, J. Chigvinadze
Faculty Publications, Chemistry
High temperature layer superconducting cuprates (HTLSC) alloys: (Bi1.7Pb0.3Sr2Can-1CunO2n+4+δ)2,n=1-9 called (2s:2:n-1:n) prepared in Uzbekistan from melts in concentrated sun flux, followed by rapid cooling, SFQA technology that preserves melt tiling by confinement of conduction layer: |(CuO2)1/2|Ca|(CuO2)1/2]n-1| in the hard shell ||, of the n=1 phase,[(CuO2)1/2|SrO|Bi1.7Pb0.3O|Bi1.7Pb0.3O|SrO|(CuO2)1/2]2. Disproportion leads to different n-phase mixing, and periodic lattice distortions (PLD) through bond resonance covalent crystalaxes: 2(rCu+2+rO-2)=4.2Å>a=3.82Å>d(CuO)+2-3/2d(O3))=3.2Å≈(cn-c1)/2(n-1). Individual phase local bonds Cu-Ca, Cu-Sr, Cu-O-Cu are ascertained by X-Ray diffraction near Cu K-edgefollowed by Cu-Ca bond scattering. The HTLSC density, ρ decrease as n increases obtains Tc,n ~180 K, identified due to n=8 phase on …
Bond Resonance In Superconducting Rapid Cooled Alloys: (Bi1.7pb0.3sr2can‐1cuno2n+4+Δ)2, N=1 To 9 Detected By Novel Local Atomic Enhanced Xrd, K Tyson, J Kmiec, Juana Acrivos, D. Gulamova, J Chigvinadze
Bond Resonance In Superconducting Rapid Cooled Alloys: (Bi1.7pb0.3sr2can‐1cuno2n+4+Δ)2, N=1 To 9 Detected By Novel Local Atomic Enhanced Xrd, K Tyson, J Kmiec, Juana Acrivos, D. Gulamova, J Chigvinadze
Faculty Publications, Chemistry
We discuss bond resonance in high temperature layer superconducting cuprates, HTLSC alloys: (Bi1.7Pb0.3Sr2Can‐1CunO2n+4+δ)2,n=1‐9 called (2s:2:n‐1:n) prepared in Uzbekistan from melts in concentrated sun flux, followed by rapid cooling, SFQA technology that preserves melt tiling, Tc,n measured in Tiblisi, and local atomic enhanced synchrotron X‐ray diffraction, XRD near the Cu K‐edge at DOE National Laboratory SLAC‐SSRL. The SFQA alloys structure indexed in the ideal D17 4h Space Group indicates (n‐1) units: (CuO2)1/2/Ca/(CuO2)1/2 are intercalated at each end of the n=1 phase [(CuO2)1/2/SrO/Bi1.7Pb0.3O/Bi1.7Pb0.3O/SrO/(CuO2)1/2]2. Surface effects lead to different n‐phase mixing, and periodic lattice distortions, PLD, through bond resonance in crystal axes: 2(rCu+2+rO‐2)=4.2Å …
Silica As A Matrix For Encapsulating Proteins:Surface Effects On Protein Structure Assessed By Circular Dichroism Spectroscopy, Daryl K. Eggers, P. J. Calabretta, M. C. Chancellor, C. Torres, G. R. Abel Jr., C. Neihaus, N. J. Birtwhistle, N. M. Khouderchah, G. H. Zemede
Silica As A Matrix For Encapsulating Proteins:Surface Effects On Protein Structure Assessed By Circular Dichroism Spectroscopy, Daryl K. Eggers, P. J. Calabretta, M. C. Chancellor, C. Torres, G. R. Abel Jr., C. Neihaus, N. J. Birtwhistle, N. M. Khouderchah, G. H. Zemede
Faculty Publications, Chemistry
The encapsulation of biomolecules in solid materials that retain the native properties of the molecule is a desired feature for the development of biosensors and biocatalysts. In the current study, protein entrapment in silica-based materials is explored using the sol-gel technique. This work surveys the effects of silica confinement on the structure of several model polypeptides, including apomyoglobin, copper-zinc superoxide dismutase, polyglutamine, polylysine, and type I antifreeze protein. Changes in the secondary structure of each protein following encapsulation are monitored by circular dichroism spectroscopy. In many cases, silica confinement reduces the fraction of properly-folded protein relative to solution, but addition …
Chemical Activity In Yba2cu3o7 − Δ Across The Normal To Superconducting Phase Transition, Juana Vivó Acrivos
Chemical Activity In Yba2cu3o7 − Δ Across The Normal To Superconducting Phase Transition, Juana Vivó Acrivos
Faculty Publications, Chemistry
The Gibbs free enthalpy, chemical activity across the transition temperature to superconductivity, Tc in YBa2Cu3O7 − δ is obtained from reciprocally enhanced X-Ray absorbance, XAS and diffraction, XRD data near the Ba L3,2 edges' energy Ea, and orientations in the X-ray beam for preferred Miller indexed [HKL] planes' scattering, that are enhanced near Tc. The standard enthalpy and entropy for the formation of mixed normal metal/superconducting domains above Tc, determined individually across the two Ba L3,2 edges, to better than a percent accuracy: ΔH≠≥ = − 220 meV, and ΔS≠≥ = − 2 meV/K when 121 ≥ T ≥ 92 …
A Bulk Water-Dependent Desolvation Energy Model For Analyzing The Effects Of Secondary Solutes On Biological Equilibria, Daryl K. Eggers
A Bulk Water-Dependent Desolvation Energy Model For Analyzing The Effects Of Secondary Solutes On Biological Equilibria, Daryl K. Eggers
Faculty Publications, Chemistry
A new phenomenological model for interpreting the effects of solutes on biological equilibria is presented. The model attributes changes in equilibria to differences in the desolvation energy of the reacting species that, in turn, reflect changes in the free energy of the bulk water upon addition of secondary solutes. The desolvation approach differs notably from that of other solute models by treating the free energy of bulk water as a variable and by not ascribing the observed shifts in reaction equilibria to accumulation or depletion of solutes next to the surfaces of the reacting species. On the contrary, the partitioning …
Speciation, Luminescence, And Alkaline Fluorescence Quenching Of 4-(2-Methylbutyl)Aminodipicolinic Acid (H2mebadpa), Gilles Muller, A. J. Ingram, A. G. Dunpal, R. Dipietro
Speciation, Luminescence, And Alkaline Fluorescence Quenching Of 4-(2-Methylbutyl)Aminodipicolinic Acid (H2mebadpa), Gilles Muller, A. J. Ingram, A. G. Dunpal, R. Dipietro
Faculty Publications, Chemistry
4-(2-Methylbutyl)aminodipicolinic acid (H2MEBADPA) has been synthesized and fully characterized in terms of aqueous phase protonation constants (pKa's) and photophysical measurements. The pKa's were determined by spectrophotometric titrations, utilizing a fully sealed titration system. Photophysical measurements consisted of room temperature fluorescence and frozen solution phosphorescence as well as quantum yield determinations at various pH, which showed that only fully deprotonated MEBADPA2– is appreciably emissive. The fluorescence of MEBADPA2– has been determined to be quenched by hydroxide and methoxide anions, most likely through base-catalyzed excited-state tautomerism or proton transfer. This quenching phenomenon has been quantitatively explored through steady-state and time-resolved fluorescence measurements. …
Changes In Apparent Molar Water Volume And Dkp Solubility Yield Insights On The Hofmeister Effect, Daryl K. Eggers, A. Y. Payumo, R. M. Huijon, D. D. Mansfield, L. M. Belk, A. K. Bui, A. E. Knight
Changes In Apparent Molar Water Volume And Dkp Solubility Yield Insights On The Hofmeister Effect, Daryl K. Eggers, A. Y. Payumo, R. M. Huijon, D. D. Mansfield, L. M. Belk, A. K. Bui, A. E. Knight
Faculty Publications, Chemistry
This study examines the properties of a 4 × 2 matrix of aqueous cations and anions at concentrations up to 8.0 M. The apparent molar water volume, as calculated by subtracting the mass and volume of the ions from the corresponding solution density, was found to exceed the molar volume of ice in many concentrated electrolyte solutions, underscoring the nonideal behavior of these systems. The solvent properties of water were also analyzed by measuring the solubility of diketopiperazine (DKP) in 2.000 M salt solutions prepared from the same ion combinations. Solution rankings for DKP solubility were found to parallel the …
The Investigation Of Epr Paramagnetic Probe Line Width And Shape Temperature Dependence In High-Temperature Superconductors Of Bi–Pb–Sr–Ca–Cu–O System, J. G. Chigvinadze, Juana Vivó Acrivos, I. G. Akhvlediani, M. I. Chubabria, T. L. Kalabegishvili, T. I. Sanadze
The Investigation Of Epr Paramagnetic Probe Line Width And Shape Temperature Dependence In High-Temperature Superconductors Of Bi–Pb–Sr–Ca–Cu–O System, J. G. Chigvinadze, Juana Vivó Acrivos, I. G. Akhvlediani, M. I. Chubabria, T. L. Kalabegishvili, T. I. Sanadze
Faculty Publications, Chemistry
The work is related with the finding out of magnetic phases in strongly anisotropic high-temperature superconductor Bi1,7Pb0,3Sr2Ca2Cu3O10-δ in the temperature region where the superconductor is in the normal state. It was studied the temperature dependence of the paramagnetic probe EPR line width. In the normal state at T>Tc near 175 K it was revealed a pick in the temperature dependence of line width. In this region it was observed the time increase of the line width with the characteristic time ~ 17 min. This shows the possibility of magnetic phase formation in this material.
Temperature Dependence Investigation Of Dissipation Processes In Strongly Anisotropic High-Temperature Superconductors Of Bi-Pb-Sr-Ca-Cu-O System Synthesized Using Solar Energy, J Chigvinadze, Juana Acrivos, S. Ashimov, D. Gulamova, T. Machaidze, D Uskenbaev
Temperature Dependence Investigation Of Dissipation Processes In Strongly Anisotropic High-Temperature Superconductors Of Bi-Pb-Sr-Ca-Cu-O System Synthesized Using Solar Energy, J Chigvinadze, Juana Acrivos, S. Ashimov, D. Gulamova, T. Machaidze, D Uskenbaev
Faculty Publications, Chemistry
The investigation of temperature dependence of damping and period of vibrations of HTSC superconductive cylinder of Bi-Pb-Sr-Ca-Cu-O system suspended by a thin elastic thread and performing axial-torsional vibrations in a magnetic field at temperatures above the critical one for the main phase Tc=107 K were carried out. It was observed some "chaos" temperature region in the temperature interval 107-138 K, where it is seen separate ripples of dissipation and oscillation frequency. It is assumed that the "chaos" region could point to a possibility of existence of other magnetic and more high-temperature phases as single islands in a normal materials matrix.
Favourable Influence Of Hydrophobic Surfaces On Protein Structure In Porous Organically-Modified Silica Glasses, Daryl K. Eggers, B. Menaa, M. Herrero, V. Rives, M. Lavrenko
Favourable Influence Of Hydrophobic Surfaces On Protein Structure In Porous Organically-Modified Silica Glasses, Daryl K. Eggers, B. Menaa, M. Herrero, V. Rives, M. Lavrenko
Faculty Publications, Chemistry
Organically-modified siloxanes were used as host materials to examine the influence of surface chemistry on protein conformation in a crowded environment. The sol–gel materials were prepared from tetramethoxysilane and a series of monosubstituted alkoxysilanes, RSi(OR′)3, featuring alkyl groups of increasing chain length in the R-position. Using circular dichroism spectroscopy in the far-UV region, apomyoglobin was found to transit from an unfolded state to a native-like helical state as the content of the hydrophobic precursor increased from 0 to 15%. At a fixed molar content of 5% RSi(OR′)3, the helical structure of apomyoglobin increased with the chain length of the R-group, …
Protein Adsorption Onto Organically-Modified Silica Glass Leads To A Different Structure Than Sol-Gel Encapsulation, Daryl K. Eggers, B, Menaa, C. Torres, M. Herrero, V. Rives, A. R.W Gilbert
Protein Adsorption Onto Organically-Modified Silica Glass Leads To A Different Structure Than Sol-Gel Encapsulation, Daryl K. Eggers, B, Menaa, C. Torres, M. Herrero, V. Rives, A. R.W Gilbert
Faculty Publications, Chemistry
The secondary structures of two proteins were examined by circular dichroism spectroscopy after adsorption onto a series of organically modified silica glasses. The glasses were prepared by the sol-gel technique and were varied in hydrophobicity by incorporation of 5% methyl, propyl, trifluoropropyl, or n-hexyl silane. Both cytochrome c and apomyoglobin were found to lose secondary structure after adsorption onto the modified glasses. In the case of apomyoglobin, the α-helical content of the adsorbed protein ranged from 21% to 28%, well below the 62% helix found in solution. In contrast, these same glasses led to a striking increase in apomyoglobin structure …
A Promising Change In The Selection Of The Circular Polarization Excitation Used In The Measurement Of Eu(Iii) Circularly Polarized Luminescence, K. Do, F. C. Muller, Gilles Muller
A Promising Change In The Selection Of The Circular Polarization Excitation Used In The Measurement Of Eu(Iii) Circularly Polarized Luminescence, K. Do, F. C. Muller, Gilles Muller
Faculty Publications, Chemistry
A judicious change in the selected transition used for circular polarization excitation will overcome the low oscillator strength limitation of the currently allowed magnetic-dipole 5D1 ← 7F2 (Eu(III)) transition chosen for circularly polarized luminescence (CPL) measurement. The proposed allowed magnetic-dipole 5D1 ← 7F0 (Eu(III)) transition will facilitate the detection of CPL from the Eu(III) systems of interest. CPL on the acetonitrile solution of the chiral tris complex of Eu(III) with (R,R)-N,N′-bis(1-phenylethyl)-2,6-pyridinedicarboxamide ([Eu((R,R)-1)3]3+), recently suggested as an effective and reliable CPL calibrating agent, confirms the feasibility of the proposed experimental procedure. A comparable CPL activity exhibited by the acetonitrile solution of …
Hydrophobic, Organically-Modified Silica Gels Enhance The Structure Of Encapsulated Apomyoglobin, Daryl K. Eggers, V. A. Rocha
Hydrophobic, Organically-Modified Silica Gels Enhance The Structure Of Encapsulated Apomyoglobin, Daryl K. Eggers, V. A. Rocha
Faculty Publications, Chemistry
Insertion of hydrophobic groups in a silica matrix, by addition of propyl- or trifluoropropyltrimethoxysilane, leads to a surprising increase in the helical content of apomyoglobin following encapsulation by the sol–gel technique