We study the influence of truncating the electrostatic interactions in a fully hydrated pure dipalmitoylphosphatidylcholine (DPPC) bilayer through 20 ns molecular dynamics simulations. The computations in which the electrostatic interactions were truncated are compared to similar simulations using the particle-mesh Ewald (PME) technique. All examined truncation distances (1.8-2.5 nm) lead to major effects on the bilayer properties, such as enhanced order of acyl chains together with decreased areas per lipid. The results obtained using PME, on the other hand, are consistent with experiments. These artifacts are interpreted in terms of radial distribution functions g(r) of molecules and molecular groups in the bilayer plane. Pronounced maxima or minima in g(r) appear exactly at the cutoff distance indicating that the truncation gives rise to artificial ordering between the polar phosphatidyl and choline groups of the DPPC molecules. In systems described using PME, such artificial ordering is not present.
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http://dx.doi.org/10.1016/S0006-3495(03)75094-2 | DOI Listing |
ACS Nano
January 2025
Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093, United States.
The structure and dynamics of water at charged graphene interfaces fundamentally influence molecular responses to electric fields with implications for applications in energy storage, catalysis, and surface chemistry. Leveraging the realism of the MB-pol data-driven many-body potential and advanced path-integral quantum dynamics, we analyze the vibrational sum frequency generation (vSFG) spectrum of graphene/water interfaces under varying surface charges. Our quantum simulations reveal a distinctive dangling OH peak in the vSFG spectrum at neutral graphene, consistent with recent experimental findings yet markedly different from those of earlier studies.
View Article and Find Full Text PDFJ Chem Theory Comput
January 2025
Department of Chemistry, University of California, Berkeley, California 94720, United States.
Energy decomposition analysis (EDA) based on density functional theory (DFT) and self-consistent field (SCF) calculations has become widely used for understanding intermolecular interactions. This work reports a new approach to EDA for post-SCF wave functions based on closed-shell restricted second-order Mo̷ller-Plesset (MP2) together with an efficient implementation that generalizes the successful SCF-level second-generation absolutely localized molecular orbital EDA approach, ALMO-EDA-II, and improves upon MP2 ALMO-EDA-I. The new MP2 ALMO-EDA-II provides distinct energy contributions for a frozen interaction energy containing permanent electrostatics and Pauli repulsions, polarized energy-yielding induced electrostatics, dispersion-corrected energy, and the fully relaxed energy, which describes charge transfer.
View Article and Find Full Text PDFRSC Adv
January 2025
Department of Physics and Chemistry, Faculty of Education, Alexandria University Egypt.
A novel series of azo dyes was successfully synthesized by combining amino benzoic acid and amino phenol on the same molecular framework azo linkage. The structural elucidation of these dyes was carried out using various spectroscopic techniques, including UV-vis, FT-IR, NMR spectroscopy, and HRMS. Surprisingly, the aromatic proton in some dyes exhibited exchangeability in DO, prompting a 2D NMR analysis to confirm this phenomenon.
View Article and Find Full Text PDFSci Rep
January 2025
College of Civil Engineering, Liaoning Technical University, Fuxin, 123000, China.
The adsorption of phosphate in the collected water is crucial to alleviate the crisis of phosphorus resources, which is in line with the concept of green and sustainable development of resources. In this study, based on the calcium modification technology of pyrolysis combined with chemical modification, a new type of calcium modified coal gangue (CaMCG) was prepared by using coal gangue as raw material and calcium chloride as modifier for the removal of phosphate.The optimum preparation conditions of CaMCG were obtained by response surface test: m:m=1, calcination temperature 735℃, calcination time 135 min.
View Article and Find Full Text PDFAnal Chim Acta
February 2025
Key Laboratory of Luminescence Analysis and Molecular Sensing (Ministry of Education), College of Pharmaceutical Sciences, Southwest University, Chongqing, 400715, China. Electronic address:
Background: Drug enantiomers often display distinguishable or even opposite pharmacological and toxicologic activities. Therefore it is of great necessity to discriminate enantiomers for guaranteeing safetyness and effectiveness of chiral drugs. Facile chiral discrimination has long been a noticeable challenge because of the minimal differences in physicochemical properties of enantiomers.
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