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Physical Chemistry Chemical Physics: PCCP

A Stachowicz-Kuśnierz, L Cwiklik, J Korchowiec, E Rogalska, B Korchowiec
Apart from being responsible for sufficient pulmonary compliance and preventing alveolar collapse, lung surfactant (LS) also forms the first barrier for uptake of inhaled pathogens. As such it is susceptible to damage caused by various deleterious compounds present in air, e.g. oxidants capable of oxidizing unsaturated LS lipids. This study examines the consequences of oxidizing 20% of unsaturated lipids in an LS model: a mixed 1 : 1 DPPC : POPC monolayer. POxnoPC (1-palmitoyl-2-(9-oxo-nonanoyl)-sn-glycero-3-phosphocholine) is considered as the main oxidation product...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Takao Tsuneda, Tetsuya Taketsugu
Hydrogen peroxide (H2O2) decomposition mechanisms in the absence and presence of iron ions in aqueous solution, which contain no OH radical formation, are theoretically determined. Calculating the oxygen-oxygen bond dissociation energies of H2O2, we confirmed that OH radical formation requires spin-forbidden transitions. Instead, we tested an H2O2 dimer-based decomposition mechanism and found that this mechanism provides reasonable barrier heights of 52-62 kcal mol-1, which are close to the experimental activation energy...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Douglas P Linder, Brett E Baker, Kenton R Rodgers
The Zn(ii)-(Imidazole(ate))n coordination motif occurs in numerous biochemical systems, including carbonic anhydrase and the matrix metalloproteinases (MMPs). Additionally, it has been used in synthetic materials, such as the zinc-based zeolitic imidazolate framework (ZIF) structures. Zinc centers in these systems typically act as Lewis acids that form complexes with small molecules, such as H2O, which is activated catalytically toward a number of important and useful hydrolysis reactions. The results reported herein from density functional theory (M05-2X) and ab initio (MP2 and CCSD(T)) calculations demonstrate that both the coordination number and the molecular geometry have a sizable impact on the binding strength, deprotonation energy, and acidity of the Zn(ii) coordinated water...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Mattia Melosso, Luca Bizzocchi, Filippo Tamassia, Claudio Degli Esposti, Elisabetta Canè, Luca Dore
The rotational spectrum of 15ND in its ground electronic X3Σ- state has been observed for the first time. Forty-three hyperfine-structure components belonging to the ground and ν = 1 vibrational states have been recorded with a frequency-modulation millimeter-/submillimeter-wave spectrometer. These new measurements, together with the ones available for the other isotopologues NH, ND, and 15NH, have been simultaneously analysed using the Dunham model to represent the ro-vibrational, fine, and hyperfine energy contributions...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Yuan-Jun Gao, Wen-Kai Chen, Zi-Rui Wang, Wei-Hai Fang, Ganglong Cui
Herein, we have employed B3LYP and TD-B3LYP methods with the QM/MM approach to study the thermally activated delayed fluorescence (TADF) phenomenon of two Cu(i) complexes bearing 5-(2-pyridyl)-tetrazolate (PyrTet) and phosphine (POP) ligands in the gas phase, solution, and crystal form. On the basis of spectroscopic properties, ground- and excited-state geometric and electronic structures, and related radiative and nonradiative rates, we have found that (1) the S1 and T1 excited states have clear metal-to-ligand charge transfer character from the Cu(i) atom to the PyrTet group; (2) the S1 and T1 states have a very small energy gap ΔES1-T1, less than 0...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Shenglong Gan, Longbin Chen, Yancong Feng, Yong Deng, Rui Zhou, Yingying Dou, Biao Tang, Lingling Shui, Yao Wang, Hao Li, Guofu Zhou
As a common physicochemical phenomenon, protonation can cause molecules, atoms or ions with lone-pair electrons to become charged, and can further cause some changes in their physical and chemical properties. Our study first focused on the molecular protonation process and accompanying transitions of the oil/water interface properties in an electric field. The relationship between the protonation degree increment and applied voltage was proposed as a guide for controlling the protonation via applying an electric field...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Bowen Shi, Yangyang Wang, Jingzhen Li, Xiuying Zhang, Jiahuan Yan, Shiqi Liu, Jie Yang, Yuanyuan Pan, Han Zhang, Jinbo Yang, Feng Pan, Jing Lu
Owing to their few lateral dangling bonds and enhanced gate electrostatics, two-dimensional semiconductors have attracted much attention for the fabrication of channels in next-generation field-effect transistors (FETs). Herein, combining first-principle band structure calculations with more precise quantum transport simulations, we systematically explore the interface properties between monolayer (ML) indium selenide (InSe) and a sequence of common electrodes in an FET. The ML InSe band structure is damaged by Sc, Au, Cr, Pt, and Pd electrodes but identifiable in contact with Ag, Cu, In, graphene and ML O-terminated Cr2C electrodes...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Paul Hendrik Schummel, Michel W Jaworek, Christopher Rosin, Jessica Högg, Roland Winter
Actin and tubulin, the main components of the cytoskeleton, are responsible for many different cellular functions and can be found in nearly all eukaryotic cells. The formation of filamentous actin (F-actin) as well as microtubules depends strongly on environmental and solution conditions. The self-assembly of both, actin and tubulin, has been found to be among the most pressure sensitive process in vivo. Here, we explored the effects of various types of natural cosolvents, such as urea and the osmolyte trimethylamine-N-oxide (TMAO), on the temperature- and pressure-dependent stability of their polymeric states, F-actin and microtubules...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
N L Matsko
Numerical calculations of surface and volume plasma excitations in silicon-hydrogen nanoclusters in the range Si10-Si60 and Si3H8-Si64H56 (size range 4-13.5 Å) are performed within the GW approximation. Some nanocluster structures were obtained using the evolutionary algorithm, and others were taken from the database. The applied method shows the results to be consistent with the experiments (except plasmaron artifacts) for fullerene clusters and bulk silicon along with sufficient sensitivity to allow investigatation of the effect of the cluster structure and size on the specific properties of plasma excitations...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Tobias Koch, Christiane Höppener, Nikos L Doltsinis
The potential of supramolecular transition metal coordination complexes to form robust, long-living, radiative charge transfer states makes this class of triplet state emitters ideal candidates for application as photosensitizes or in photonic devices. Antenna-enhanced phosphorescence experiments on single Ru2+-bis-terpyridine complexes incorporated into a thin PMMA film show that phosphorescence emission spectra can exhibit shifts depending on the local environment [J. F. Herrmann, P. S. Popp, A. Winter, U...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Yalan Yan, Hao Liu, Yonghao Han, Fangfei Li, Chunxiao Gao
At ambient conditions, the lattice structure of supported ultrathin transition metal dichalcogenides (TMDs) can be effectively modified by a substrate. When compressed, the effect of substrate is far from settled. In this study, the effects of an Si substrate on the lattice structures of compressed monolayer and multilayer ReS2 were investigated by performing high-pressure Raman measurements and first-principle calculations. Our results revealed substrate-affected strain in compressed monolayer ReS2, which resulted in a distorted unit with S atoms sliding within a single layer...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Olatz Uranga-Barandiaran, Manon Catherin, Elena Zaborova, Anthony D'Aléo, Frédéric Fages, Frédéric Castet, David Casanova
In this work we present the synthesis, characterization and theoretical investigation of three boron-difluoride-curcuminoid derivatives and their covalent homodimers chemically linked through a polymethylenic chain. Low-lying electronic excited states and photophysical properties of the monomeric species have been described as the convolution of different donor-acceptor intramolecular excitations. Covalent dimers in solution can present open or folded structural conformations. Analysis of absorption profiles and computational results allow to identify the factors that control the relative stability of the two forms and rationalize its dependence with the solvent polarity...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Xiaojing Cong, Jérôme Golebiowski
G protein-coupled receptors (GPCRs) control most cellular communications with the environment and are the largest protein family of drug targets. As strictly regulated molecular machines, profound comprehension of their activation mechanism is expected to significantly facilitate structure-based drug design. This study provides atomistic-level description of the activation dynamics of the C-X-C chemokine receptor type 4 (CXCR4), a class A GPCR and important drug target. Using molecular dynamics and enhanced sampling, we demonstrate how mutations and protonation of conserved residues trigger activation through microswitches at the receptor core, while sodium ion - a known allosteric modulator - inhibits it...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Daniel Stone, Kendrew Au, Samantha Sime, Diogo J Medeiros, Mark Blitz, Paul W Seakins, Zachary Decker, Leonid Sheps
Decomposition kinetics of stabilised CH2OO and CD2OO Criegee intermediates have been investigated as a function of temperature (450-650 K) and pressure (2-350 Torr) using flash photolysis coupled with time-resolved cavity-enhanced broadband UV absorption spectroscopy. Decomposition of CD2OO was observed to be faster than CH2OO under equivalent conditions. Production of OH radicals following CH2OO decomposition was also monitored using flash photolysis with laser-induced fluorescence (LIF), with results indicating direct production of OH in the v = 0 and v = 1 states in low yields...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Anuj Bhargava, Cindy Y Chen, Kenneth D Finkelstein, Matthew J Ward, Richard D Robinson
Cation site occupation is an important determinant of materials properties, especially in a complex system with multiple cations such as in ternary spinels. Many methods for extracting the cation site information have been explored in the past, including analysis of spectra obtained through K-edge X-ray absorption spectroscopy (XAS). In this work, we measure the effectiveness of X-ray emission spectroscopy (XES) for determining the cation site occupation. As a test system we use spinel phase CoxMn3-xO4 nanoparticles contaminated with CoO phases because Co and Mn can occupy all cation sites and the impurity simulates typical products of oxide syntheses...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Todor Dudev, Sonia Ilieva, Lyudmila Doudeva
Selecting the "right" metal cation from the surrounding intracellular/extracellular fluids is of crucial importance for proper functioning of metalloproteins. Over the course of a few billion years of cell evolution various strategies have been developed by the host protein or cell machinery to secure the most favorable conditions for cognate cation binding. The effect of internal/external electric fields, potentially capable of influencing the process of metal selectivity in proteins, however, remains an enigmatic and unexplored area of research...
September 21, 2018: Physical Chemistry Chemical Physics: PCCP
Elia Grueso, Emilio Roldan, Pilar Perez-Tejeda, Edyta Kuliszewska, Blanca Molero, Lothar Brecker, R M Giráldez-Pérez
The interaction between calf thymus DNA and the gemini surfactants N,N'-[α,ω-phenylenebis(methylene)bis [N,N'-dimethyl-N-(1-hexadecyl)]-ammonium dibromide], p-16-Ph-16 (α = 1, ω = 3) and m-16-Ph-16 (α = 1, ω = 2), has been investigated via circular dichroism, fluorescence and UV-vis spectroscopy, zeta potential, dynamic light scattering, and AFM microscopy. Measurements were carried out in aqueous media at different molar ratios, R = (C16-Ph-16)/CDNA and C16-Ph-16 always below the critical micellar concentration (CMC) of the surfactant...
September 20, 2018: Physical Chemistry Chemical Physics: PCCP
Tapta Kanchan Roy, Vladimir Kopysov, Aleksandr Pereverzev, Jiří Šebek, R Benny Gerber, Oleg V Boyarkin
The intrinsic structure of an opioid peptide [Ala2, Leu5]-leucine enkephalin (ALE) has been investigated using first-principles based vibrational self-consistent field (VSCF) theory and cold ion spectroscopy. IR-UV double resonance spectroscopy revealed the presence of only one highly abundant conformer of the singly protonated ALE, isolated and cryogenically cooled in the gas phase. High-level quantum mechanical calculations of electronic structures in conjunction with a systematic conformational search allowed for finding a few low-energy candidate structures...
September 20, 2018: Physical Chemistry Chemical Physics: PCCP
Taylor A Barnes, Liwen F Wan, Paul R C Kent, David Prendergast
Rechargeable batteries that utilize divalent Mg ions as the charge carrier species can in principle achieve substantially greater volumetric energy densities than conventional Li-ion batteries. One significant impediment to the development of commercially viable Mg-ion batteries is the slow rate of Mg ion diffusion through otherwise promising cathode materials. Accurate prediction of the activation energies associated with this diffusion process using density functional theory (DFT) is especially challenging due to self-interaction errors intrinsic to DFT that lead to over-delocalization of the d-electrons...
September 20, 2018: Physical Chemistry Chemical Physics: PCCP
Jingxiang Guo, Jeremy C Palmer
We perform large-scale molecular dynamics (MD) simulations of systems with up to 216 000 atoms to study the low-temperature behavior of the mWAC model of silica. Recent studies show that mWAC exhibits a liquid-liquid phase transition (LLPT), similar to the one hypothesized to occur in deeply supercooled water. Characterization of mWAC's small-angle scattering behavior reveals an anomalous increase in fluctuations in density and local tetrahedral order in the liquid upon cooling. Moreover, the static correlation length computed from the anomalous scattering component exhibits power-law growth as temperature decreases and appears to diverge near 3300 K...
September 20, 2018: Physical Chemistry Chemical Physics: PCCP
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