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Journal of Physical Chemistry. B

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https://www.readbyqxmd.com/read/28535355/effect-of-composition-asymmetry-on-the-phase-separation-and-crystallization-in-double-crystalline-binary-polymer-blends-a-dynamic-monte-carlo-simulation-study
#1
Ashok Kumar Dasmahapatra
Polymer blends offer an exciting material for various potential applications due to their tunable properties by varying constituting components and their relative composition. Our simulation results unravel an intrinsic relationship between crystallization behavior and composition asymmetry. We report simulation results for non-isothermal and isothermal crystallization with weak and strong segregation strength to elucidate the composition dependent crystallization behavior. With increasing composition of low melting B-polymer, macrophase separation temperature changes non-monotonically, which is attributed to the non-monotonic change in diffusivity of both the polymers...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28535066/marangoni-flow-induced-evaporation-enhancement-on-binary-sessile-drops
#2
Pin Chen, Souad Harmand, Safouene Ouenzerfi, Jesse Schiffler
The evaporation processes of pure water, pure 1-butanol, and 5% 1-butanol aqueous solution drops on heated hydrophobic substrates are investigated to determine the effect of temperature on the drop evaporation behavior. The evolution of the parameters (contact angle, diameter, and volume) during evaporation measured using a drop shape analyzer and the infrared thermal mapping of the drop surface recorded by an infrared camera were used in investigating the evaporation process. The pure 1-butanol drop does not show any thermal instability at different substrate temperatures, while the convection cells created by the thermal Marangoni effect appear on the surface of the pure water drop from 50°C...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28535056/solid-state-nmr-structure-based-inhibitor-design-to-achieve-selective-inhibition-of-the-parallel-in-register-%C3%AE-sheet-versus-antiparallel-iowa-mutant-%C3%AE-amyloid-fibrils
#3
Qinghui Cheng, Wei Qiang
Solid-state nuclear magnetic resonance (ssNMR) spectroscopy has been widely applied to characterize the high-resolution structures of β-amyloid (Aβ) fibrils. While these structures provide crucial molecular insights on the deposition of amyloid plaques in Alzheimer's diseases (AD), ssNMR structures have been rarely used so far as basis for designing inhibitors. It remains a challenge because the ssNMR-based Aβ fibrils structures were usually obtained with sparsely-isotope-labeled peptides with limited experimental constraints, where the structural models, especially the side-chain coordinates showed restricted precision...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28535053/the-origin-of-ion-pairing-and-redissociation-of-ionic-liquid
#4
Bong-Seop Lee, Shiang-Tai Lin
We address the possible occurrence of a minimum extent of dissociation (α) of ionic liquid (IL) in IL-solvent mixtures. This phenomenon, known as the re-dissociation of IL, is responsible for many interesting composition-dependent properties in such mixtures. A predictive thermodynamic model is developed to provide semi-quantitative description on the change of α with solvent concentration. It is found that the occurrence of minimum α coincides with the occurrence maximum mean activity coefficient of dissociated ions, indicating better solvation of free, dissociated ions both with decreasing and increasing solvent concentration...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28535051/structural-properties-of-nonionic-monorhamnolipid-aggregates-in-water-studied-by-classical-molecular-dynamics-simulations
#5
Elango Munusamy, Charles M Luft, Jeanne E Pemberton, Steven D Schwartz
Molecular dynamics simulations were carried out to investigate the structure and stabilizing factors of aggregates of the nonionic form of the most common congener of monorhamnolipids, α-rhamnopyranosyl-β-hydroxydecanoyl-β-hydroxydecanoate (Rha- C10-C10), in water. Aggregates of size ranging from 5 monomers to 810 monomers were observed in the simulation forming spherical and ellipsoidal structures, a torus like structure and a unilamellar vesicle. The effects of hydrophobic chain conformation and alignment in the aggregate, role of H-bonds between monomer...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28534622/solute-partitioning-in-micelles-combining-molecular-dynamics-simulations-cosmomic-and-experiments
#6
Denitsa Yordanova, Eric Ritter, Thomas Gerlach, Jan-Hendrik Jensen, Irina Smirnova, Sven Jakobtorweihen
The partition equilibria of solutes between micelles and an aqueous phase is a key factor in many applications. Depending on the task, many micelle-solute combinations are possible. Therefore, theoretical methods to predict the partition behavior in micellar systems are needed. Here, two predictive methods are evaluated and compared. First, it is shown how molecular dynamics simulations (MD) with the umbrella sampling method can be used to calculate free energy profiles in micellar systems. The second applied method is an extension of the COSMO-RS theory to anisotropic systems termed COSMOmic...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28534618/microsecond-timescale-proton-rotating-frame-relaxation-under-magic-angle-spinning
#7
Petra Rovó, Rasmus Linser
This paper deals with the theoretical foundation of proton magic-angle-spinning rotating-frame relaxation (R1ρ) and establishes the range of validity and accuracy of the presented approach to describe low-amplitude microsecond timescale motion in the solid state. Beside heteronuclear dipolar and chemical shift anisotropy interactions, a major source of relaxation for protons is the homonuclear dipolar interaction. For this latter relaxation process no general analytical equation has been published until now which would describe the R1ρ relaxation at any spinning-speed, spin-lock field, or tilt-angle...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28534408/modulation-of-the-conformational-dynamics-of-apo-adenylate-kinase-through-a-%C3%AF-cation-interaction
#8
Ritaban Halder, Rabindra Nath Manna, Sandipan Chakraborty, Biman Jana
Large scale conformational transition from open to closed state of adenylate kinase (ADK) is essential for its catalytic cycle. Apo-ADK undergoes conformational transition in such a way that closely resembles open to closed conformational transition. Here, equilibrium simulations, free energy simulations, QM/MM calculations in combination with several bioinformatics approaches have been used to explore the molecular origin of this conformational transition in apo-ADK. Apart from its conventional open state, E...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28492328/inhibition-of-radiolytic-molecular-hydrogen-formation-by-quenching-of-excited-state-water
#9
Gregory P Horne, Simon M Pimblott, Jay A LaVerne
Comparison of experimental measurements of the yield of molecular hydrogen produced in the gamma radiolysis of water and aqueous nitrate solutions with predictions of a Monte Carlo track chemistry model shows that the nitrate anion scavenging of the hydrated electron, its precursor, and hydrogen atom cannot account for the observed decrease in the yield at high nitrate anion concentrations. Inclusion of the quenching of excited states of water (formed by either direct excitation or reaction of the water radical cation with the precursor to the hydrated electron) by the nitrate anion into the reaction scheme provides excellent agreement between the stochastic calculations and experiment demonstrating the existence of this short-lived species and its importance in water radiolysis...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28489951/direct-observation-of-changes-in-focal-conic-domains-of-cholesteric-films-induced-by-ultraviolet-irradiation
#10
Olga V Sinitsyna, Alexey Yu Bobrovsky, Georgy B Meshkov, Igor V Yaminsky, Valery P Shibaev
The helical supramolecular structure of cholesteric liquid crystalline (LC) films predetermines their outstanding optical properties and the unique nanostructure of their surface. The introduction of photochromic dopants in these films opens up an interesting possibility for creation of smart cholesteric materials with photocontrollable optical and photovariable surface properties. Using atomic force microscopy (AFM), we performed in situ measurements of the surface topography of cyclosiloxane LC cholesteric oligomer films during the cholesteric helix twisting caused by their preliminary ultraviolet (UV) irradiation...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28485937/characterization-of-kcne1-inside-lipodisq-nanoparticles-for-epr-spectroscopic-studies-of-membrane-proteins
#11
Indra D Sahu, Rongfu Zhang, Megan M Dunagan, Andrew F Craig, Gary A Lorigan
EPR spectroscopic studies of membrane proteins in a physiologically relevant native membrane-bound state are extremely challenging due to the complexity observed in inhomogeneity sample preparation and dynamic motion of the spin-label. Traditionally, detergent micelles are the most widely used membrane mimetics for membrane proteins due to their smaller size and homogeneity, providing high-resolution structure analysis by solution NMR spectroscopy. However, it is often difficult to examine whether the protein structure in a micelle environment is the same as that of the respective membrane-bound state...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28482661/insights-into-formation-and-structure-of-a%C3%AE-oligomers-cross-linked-via-tyrosines
#12
Shuting Zhang, Dillion M Fox, Brigita Urbanc
Alzheimer's disease (AD) pathology is hypothesized to be triggered by amyloid β-protein (Aβ) assembly into oligomers. Oligomer size distributions of both predominant Aβ alloforms, Aβ40 and Aβ42, can be determined in vitro using cross-linking followed by gel electrophoresis. Cross-linking, which can occur in vivo in the presence of copper and hydrogen peroxide, was recently shown to stabilize Aβ oligomers by inhibiting their conversion into fibrils. Whereas several studies showed that cross-linking is facilitated by dityrosine bond formation, the molecular-level mechanism of cross-linking remains unclear...
May 23, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28531354/monomeric-polyglutamine-structures-that-evolve-into-fibrils
#13
David Punihaole, Ryan S Jakubek, Riley James Workman, Lauren E Marbella, Patricia Campbell, Jeffry D Madura, Sanford A Asher
We investigate the solution and fibril conformations and structural transitions of the polyglutamine (polyQ) peptide, D2Q10K2 (Q10), by synergistically using UV Resonance Raman (UVRR) spectroscopy and Molecular Dynamics (MD) simulations. We show that Q10 adopts two distinct, monomeric solution conformational states, a collapsed β-strand and a PPII-like structure that do not readily interconvert. This clearly indicates a high activation barrier in solution that prevents equilibration between these structures...
May 22, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28531353/comprehensive-thermodynamic-profiling-for-the-binding-of-a-g-quadruplex-selective-indoloquinoline
#14
Andrea Funke, Klaus Weisz
Binding of a positively charged indoloquinoline derivative to a G-quadruplex formed by the G-rich promoter element of the c-MYC oncogene was subjected to a rigorous isothermal calorimetric analysis. Binding of the indoloquinoline is primarily enthalpy-driven but is also promoted by a favorable entropy term. Both binding enthalpy ΔH° and binding entropy ΔS° exhibit a noticeable temperature dependence with almost complete enthalpy-entropy compensation as a result of a negative change in heat capacity ΔCp°...
May 22, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28530813/enhanced-sampling-of-phase-transitions-in-coarse-grained-lipid-bilayers
#15
David N Stelter, Tom Keyes
Freezing and melting of dipalmitoylphosphatidylcholine (DPPC) bilayers are simulated in both the explicit (Wet) and implicit solvent (Dry) coarse-grained MARTINI force fields with enhanced sampling, via the isobaric, molecular dynamics version of the generalized replica exchange method (gREM). Phase transitions are described with the entropic viewpoint, based upon the statistical temperature as a function of enthalpy, TS(H) = 1/(dS(H)/dH), where S is the configurational entropy. Bilayer thickness, area per lipid, and the second-rank order parameter (P2) are calculated vs temperature in the transition range...
May 22, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28530400/probing-the-conformation-dependent-preferential-binding-of-ethanol-to-cationic-glycylalanylglycine-in-water-ethanol-by-vibrational-and-nmr-spectroscopy
#16
David DiGuiseppi, Bridget J Milorey, Gabrielle Lewis, Nina Kubatova, Stefanie Farrell, Harald Schwalbe, Reinhard Schweitzer-Stenner
The conformational propensity of amino acid residues is determined by an intricate balance of peptide-solvent and solvent-solvent interactions. In order to explore how the systematic replacement of water by a cosolvent affects the solvation of both amino acid backbone and side chains we, performed a combined vibrational spectroscopy and NMR study of cationic glycylalanylglycine (GAG) in different ethanol/water mixtures between 0 and 42 mole percent of ethanol. The classical model peptide N'-methylacetamide was used as a reference system to probe solvent-induced spectroscopic changes...
May 22, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28463496/interfacial-phenomena-and-mechanical-behavior-of-polyetheretherketone-polybenzimidazole-blend-under-hygrothermal-environment
#17
Peng Liu, Michael Mullins, Tim Bremner, Natalie Benner, Hung-Jue Sue
Demands for engineering applications of high performance polymers, such as the polyaryletherketone families, have grown significantly in recent years. Fundamental knowledge on the mechanical behavior of such polymers, especially under harsh environments, is still lacking. In this study, the mechanical behavior and interfacial phenomena of a blend of polybenzimidazole (PBI) particles having sizes of about 50 μm and polyetheretherketone (PEEK) matrix at 50:50 weight ratio was characterized. PBI and PEEK are known to be incompatible with each other in the dry state...
May 22, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28525718/on-the-stability-of-the-parent-anion-of-the-potential-radiosensitizer-8-bromoadenine-formed-by-low-energy-3-ev-electron-attachment
#18
Robin Schürmann, Katrin Tanzer, Iwona Dabkowska, Stephan Paul Denifl, Ilko Bald
8-Bromoadenine (8BrA) is a potential DNA radiosensitizer for cancer radiation therapy due to its efficient interaction with low energy electrons (LEEs). LEEs are a short-living species generated during the radiation damage of DNA by high energy radiation as it is applied in cancer radiation therapy. Electron attachment to 8BrA in the gas phase results in a stable parent anion below 3 eV electron energy in addition to fragmentation products formed by resonant exocyclic bond cleavages. Density functional theory (DFT) calculations of the 8BrA- anion reveal an exotic bond between the bromine and the C8 atom with a bond length of 2...
May 19, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28525712/engineering-hydrogen-bonding-interaction-and-charge-separation-in-bio-polymers-for-green-lubrication
#19
Liwen Mu, Yijun Shi, Jing Hua, Wei Zhuang, Jiahua Zhu
Synthetic additives are widely used in lubricants nowadays to upgrade lubrication properties. The potential of integrating sustainable components in modern lubricants has rarely been studied yet. In this work, two sustainable resources lignin and gelatin have been synergistically incorporated into ethylene glycol (EG) and their tribological properties were systematically investigated. The abundant hydrogen bonding sites in lignin and gelatin as well as their inter-chain interaction via hydrogen bonding play the dominating roles in tuning the physicochemical properties of the mixture and improving lubricating properties...
May 19, 2017: Journal of Physical Chemistry. B
https://www.readbyqxmd.com/read/28525711/protein-partial-molar-volumes-in-multi-component-solutions-from-the-perspective-of-inverse-kirkwood-buff-theory
#20
Cesar Calero-Rubio, Curtis M Strab, Gregory V Barnett, Christopher J Roberts
Inverse Kirkwood-Buff (KB) solution theory can be used to relate macroscopic quantities with molecular scale interactions and correlation functions, in the form of KB integrals. Protein partial specific volumes (<HAT>V</HAT>2) from high-precision density measurements can be used to quantify solvent-solute and solute-solute KB integrals. Currently, general expressions for <HAT>V</HAT>2 as a function of co-solute concentration (c3) have been provided for only binary and ternary solutions...
May 19, 2017: Journal of Physical Chemistry. B
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