Molecular Dynamics Study of the Electric and Dielectric Properties of Model DPPC and Dicaprin Insoluble Monolayers: Size Effect

Tzvetanov, Stanislav; Shushkov, Philip; Velinova, Maria; Ivanova, Anela; Tadjer, Alia

doi:10.1021/la9047352

Cited by 5 publications

(10 citation statements)

References 60 publications

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“…a; denoted below as DPPC ). Their initial coordinates in a monolayer are taken from a previous work . The second leaflet is obtained by reflection and translation of this monolayer along z (which is the direction normal to the interface in the entire work) so that the lipid tails are in close proximity.…”

Section: Models and Methodsmentioning

confidence: 99%

Testing the limits of model membrane simulations—bilayer composition and pressure scaling

Ivanova

2017

J Comput Chem

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Studying transfer of bioactive compounds across cell membranes by simulations attracts growing attention. To perform such calculations accurately, it is necessary to verify the validity of computational protocols established for description of unperturbed lipid bilayers also with translocating substances present. The current work reports the results from 1 μs long atomistic molecular dynamics simulations of two types of model plasma membranes-one built of a single phospholipid (DPPC) and one constructed of four types of phospholipids-in the presence of a drug-peptide complex experimentally known to cross cell membranes. The influence of membrane composition and of applied pressure scaling algorithm on the simulations outcome is analyzed with particular focus on membrane structure and on complex-lipid interactions during the initial penetration stage. It is found that the mixed composition of the membrane is important for correct assessment of the interactions with the complex both from purely structural perspective and because of the uneven charge distribution. The structure of the mixed lipid bilayer is affected more markedly by the pressure scaling algorithm. When the pressure is isotropically scaled, lipids are distributed almost homogeneously along the membrane in liquid ordered state. On semi-isotropic scaling, the lipid tails undergo significant rearrangement and a long-range ordered state is established. This results in "freezing" of the membrane and expulsion of the complex. The statistical analysis of the MD data points to the conclusion that a mixed-lipid membrane model with isotropic pressure scaling would be more suitable for describing the process of complex translocation across neoplastic membranes. © 2017 Wiley Periodicals, Inc.

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Section: Models and Methodsmentioning

confidence: 99%

Testing the limits of model membrane simulations—bilayer composition and pressure scaling

Ivanova

2017

J Comput Chem

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“… Upon monolayer compression, hexagonally ordered subphases are expected for any lipids that have a phase coexistence region in their pressure–area isotherms (e.g., DMPS and DPPC). This effect was described for the DPPC monolayer in both coarse grain simulations and all-atom simulations. , The reduction in the tail layer thickness upon monolayer dilution may not depend on the nature of the lipid. Indeed, this was demonstrated in spectroscopic studies of the DPPC monolayer and in MD simulations of the same monolayer …”

Section: Results and Discussionmentioning

confidence: 90%

“…Note that a similar approach to study the nature of the dipole potential was performed by MD simulations of DPPC monolayers. 22 The authors decomposed the potential into two subsystems and compared the inputs at different monolayer densities. They identified a similar behavior between water and lipid inputs under monolayer compression in the noticeably smaller A range from 40 to 70 Å 2 .…”

Section: Upon Monolayer Compression Hexagonally Orderedmentioning

confidence: 99%

“…21 It is important to note that MD methods have allowed one to study the changes in the electric potential distribution accompanied by DPPC monolayer compaction. 22 We found only one example of an application of the MD method to monolayers of anionic lipids, 23 although there were no details regarding electrostatic phenomena. Therefore, we focus on the electrostatic potentials in monolayers of a negatively charged DMPS lipid.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The LE–LC phase transitions and hexagonal ordering occurring, for example, in a DPPC monolayer, were successfully simulated in two independent all-atom MD studies. , Coarse-grained approaches are also often used for similar systems . It is important to note that MD methods have allowed one to study the changes in the electric potential distribution accompanied by DPPC monolayer compaction . We found only one example of an application of the MD method to monolayers of anionic lipids, although there were no details regarding electrostatic phenomena.…”

Section: Introductionmentioning

confidence: 99%

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Comprehensive Study of the Liquid Expanded–Liquid Condensed Phase Transition in 1,2-Dimyristoyl-sn-glycero-3-phospho-l-serine Monolayers: Surface Pressure, Volta Potential, X-ray Reflectivity, and Molecular Dynamics Modeling

et al. 2019

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An integrated approach is applied to reveal fine changes in the surface-normal structure of 1,2-dimyristoyl-sn-glycero-3-phospho-Lserine (DMPS) monolayers at the air−lipid−water interface occurring in a liquid expanded (LE)−liquid condensed (LC) transition. The combination of the Langmuir monolayer technique, X-ray reflectometry, and molecular dynamics (MD) modeling provides new insight into the molecular nature of electrostatic phenomena in different stages of lipid compression. A homemade setup with a laboratory X-ray source (λ = 1.54 Å) offers a nondestructive way to reveal the structural difference between the LE and LC phases of the lipid. The electron density profile in the direction normal to the interface is recovered from the X-ray reflectivity data with the use of both model-independent and model-based approaches. MD simulations of the DMPS monolayer are performed for several areas per lipid using the all-atom force field. Using the conventional theory of capillary waves, a comparison is made between the electron density profiles reconstructed from the X-ray data and those calculated directly from MD modeling, which demonstrates remarkable agreement between the experiment and simulations for all selected lipid densities. This confirms the validity of the simulations and allows an analysis of the contributions of the hydrophobic tails and hydrated polar groups to the electron density profile and to the dipole component of the electric field at the interface. According to the MD data, the dependence of the Volta potential on the area per lipid in the monolayer has a different molecular nature below and above the phase transition. In the LE state of the monolayer, the potential is determined mostly by the oriented water molecules in the polar region of the lipid. In the LE−LC transition, these molecules are displaced to the bulk, and their effect on the Volta potential becomes insignificant compared with the contribution of the hydrophobic tails. The hydrophobic tails are highly ordered in the state of the liquid crystal so that their dipole moments entirely determine the growth of the potential upon compression up to the monolayer collapse.

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Computer simulations of lung surfactant

Baoukina

Tieleman

2016

Biochimica et Biophysica Acta (BBA) - Biomembranes

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Lung surfactant lines the gas-exchange interface in the lungs and reduces the surface tension, which is necessary for breathing. Lung surfactant consists mainly of lipids with a small amount of proteins and forms a monolayer at the air-water interface connected to bilayer reservoirs. Lung surfactant function involves transfer of material between the monolayer and bilayers during the breathing cycle. Lipids and proteins are organized laterally in the monolayer; selected species are possibly preferentially transferred to bilayers. The complex 3D structure of lung surfactant and the exact roles of lipid organization and proteins remain important goals for research. We review recent simulation studies on the properties of lipid monolayers, monolayers with phase coexistence, monolayer-bilayer transformations, lipid-protein interactions, and effects of nanoparticles on lung surfactant. This article is part of a Special Issue entitled: Biosimulations edited by Ilpo Vattulainen and Tomasz Róg.

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Molecular Dynamics Study of the Electric and Dielectric Properties of Model DPPC and Dicaprin Insoluble Monolayers: Size Effect

Cited by 5 publications

References 60 publications

Testing the limits of model membrane simulations—bilayer composition and pressure scaling

Testing the limits of model membrane simulations—bilayer composition and pressure scaling

Comprehensive Study of the Liquid Expanded–Liquid Condensed Phase Transition in 1,2-Dimyristoyl-sn-glycero-3-phospho-l-serine Monolayers: Surface Pressure, Volta Potential, X-ray Reflectivity, and Molecular Dynamics Modeling

Computer simulations of lung surfactant

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