Hydration strongly affects the molecular and electronic structure of membrane phospholipids

Mashaghi, Alireza; Partovi–Azar, Pouya; Jadidi, Tayebeh; Nafari, N.; Maass, Philipp; Tabar, M. Reza Rahimi; Bonn, Mischa; Bakker, Huib J.

doi:10.1063/1.3694280

Cited by 54 publications

(45 citation statements)

References 44 publications

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“…The dipole moment is ∼10 D, several fold larger than the dipole moment of a water molecule. 15,28 Electric field-induced enhancement of water dissociation has been experimentally observed previously using field emitter tips where the surface electric fields are estimated to be on the order of 1 V/Å. 27 Fields of this magnitude distort molecules, induce ionization and break bonds, and thus lead to an increased dissociation constant of interfacial water.…”

Section: −25mentioning

confidence: 99%

“…The electronic properties and vibrational eigenmodes of the above structures, i.e., pure and hydrated DPPC samples, are reported in our two most recent works 15,16 Generally speaking, obtaining a negative (imaginary, because what is obtained is actually ω 2 rather the ω) frequencies is a signature of having an unstable structure that is energetically very sensitive to small changes in atomic positions. It has been shown that apart from three, and only three, frequencies with |ω| < 0.1 cm −1 (corresponding to three acoustic modes), all the other eigenfrequencies (total 390 eigenfrequencies for pure, 570 for DPPC/(H 2 O) 20 , and 840 for DPPC/(H 2 O) 50 ) are positive.…”

Section: ■ Computational Detailsmentioning

confidence: 99%

“…The structures and electronic properties turn out to be quite independent of the inclusion of the vdW functional. 15 For example, the difference between the length of the lipid in vdW calculation (28.30 Å) and the reported LDA calculation (28.24 Å) is less than 0.3% (please see ref 15).…”

Section: ■ Computational Detailsmentioning

confidence: 99%

“…26,27 The interfacial water is subject to a strong electric field of the lipid, 15 which originates primarily from the large dipole moment associated with the negatively charged phosphate and the positively charged choline groups of the DPPC molecule. The dipole moment is ∼10 D, several fold larger than the dipole moment of a water molecule.…”

Section: −25mentioning

confidence: 99%

“…The relaxed configuration obtained from this arrangement resembles the structural unit of a membrane monolayer. 15 In this case, we use periodic boundary conditions, with a 3 × 3 × 1 Brillouin-zone sampling. We also let the unit cell be optimized at the same time with the atoms with the maximum stress tolerance set to 0.25 GPa.…”

Section: ■ Computational Detailsmentioning

confidence: 99%

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Enhanced Autoionization of Water at Phospholipid Interfaces

et al. 2012

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ABSTRACT:The structure and autoionization of water at the water−phospholipid interface are investigated by ab initio molecular dynamics and ab initio Monte Carlo simulations using local density approximation (LDA) and generalized gradient approximation (GGA) for the exchange−correlation energy functional. Depending on the lipid headgroup, strongly enhanced ionization is observed, leading to the dissociation of several water molecules into H + and OH − per lipid. The results can shed light on the phenomena of the high proton conductivity along membranes that has been reported experimentally. ■ INTRODUCTIONPhospholipids are amphiphilic molecules that, in an aqueous environment, self-assemble into bilayers and form the major structural constituents of biomembranes. Although the affinity of the lipid's headgroup to interfacial water has been widely addressed in the literature, 1,2 the exact chemical nature of this coupling is not fully understood and its strength remains to be quantified. In particular, it is not clear how this coupling affects the structure and dynamics of the interfacial water layer and the proton transport. Enhanced proton conduction along phospholipid−water interfaces was first observed in the mid 1980s.3,4 Recent studies by means of scanning tunneling microscopy (STM) confirm a significant lateral conductivity. This conductivity is believed to be of functional importance because lateral proton diffusion along membrane surfaces represents the most efficient pathway for H + transport between protein pumps. 6 The molecular mechanism underlying the high lateral proton conductivity has not yet been resolved. 7−11In this paper we report ab initio molecular dynamics (AIMD) and ab initio Monte Carlo (AIMC) simulations of interfacial water covering the headgroup of zwitterionic dipalmitoyl−phosphatidylcholine (DPPC) molecule. We perform calculations within the local density approximation and generalized gradient approximation for the exchange−correlation energy functional, with Ceperley−Alder 12 and Perdew− Burke−Ernzerhof 13 parametrizations, respectively. We show that the interfacial water exhibits a strongly enhanced autoionization that is caused by the presence of strong local electric field as well as strong hydrogen bonding. ■ COMPUTATIONAL DETAILSGround State Calculations. To calculate the ground state structure of the DPPC molecule, we first build the molecule by putting atoms together with coordinations according to the bonding rules from chemistry. To relax this structure, density functional theory (DFT) is applied as implemented in the SIESTA code.14 To this end, the DPPC molecule is placed in a unit cell with dimensions much larger than the size of the molecule. The spatial extension of the pure DPPC structure is ≈4 × 29 × 8 Å. We choose a box of 20 × 40 × 20 Å dimensions. As a consequence, because we are dealing with a molecule (a cluster), no periodic boundary conditions are adopted and only the Γ point in the reciprocal space is needed for the energy integration. The mesh cutoff is set to...

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Section: −25mentioning

confidence: 99%

Section: ■ Computational Detailsmentioning

confidence: 99%

Section: ■ Computational Detailsmentioning

confidence: 99%

Section: −25mentioning

confidence: 99%

Section: ■ Computational Detailsmentioning

confidence: 99%

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Enhanced Autoionization of Water at Phospholipid Interfaces

et al. 2012

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Microscopic evaluation of vesicles shed by erythrocytes at elevated temperatures

Moore

Sorokulova

Pustovyy

et al. 2013

Microscopy Res & Technique

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The images of human erythrocytes and vesicles were analyzed by a light microscopy system with spatial resolution of better than 90 nm. The samples were observed in an aqueous environment and required no freezing, dehydration, staining, shadowing, marking, or any other manipulation. Temperature elevation resulted in significant concentration increase of structurally transformed erythrocytes (echinocytes) and vesicles in the blood. The process of vesicle separation from spiculated erythrocytes was video recorded in real time. At a temperature of 37°C, mean vesicle concentrations and diameters were found to be 1.50 ± 0.35 × 10(6) vesicles per microliter and 0.365 ± 0.065 μm, respectively. The vesicle concentration increased approximately threefold as the temperature increased from 37 to 40°C. It was estimated that 80% of all vesicles found in the blood are smaller than 0.4 μm. Accurate account of vesicle numbers and dimensions suggest that 86% of the lost erythrocyte material is lost not by vesiculation but by another, as yet, unknown mechanism.

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Biomembranes

Likhtenshtein

2021

Biological Water

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Hydration strongly affects the molecular and electronic structure of membrane phospholipids

Cited by 54 publications

References 44 publications

Enhanced Autoionization of Water at Phospholipid Interfaces

Enhanced Autoionization of Water at Phospholipid Interfaces

Microscopic evaluation of vesicles shed by erythrocytes at elevated temperatures

Biomembranes

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