Biomembrane interfaces create regions of slowed water dynamics in their vicinity. When two lipid bilayers come together, this effect is further accentuated, and the associated slowdown can affect the dynamics of larger-scale processes such as membrane fusion. We have used molecular dynamics simulations to examine how lipid and water dynamics are affected as two lipid bilayers approach each other. These two interacting fluid systems, lipid and water, both slow and become coupled when the lipid membranes are separated by a thin water layer. We show in particular that the water dynamics become glassy, and diffusion of lipids in the apposed leaflets becomes coupled across the water layer, while the "outer" leaflets remain unaffected. This dynamic coupling between bilayers appears mediated by lipid-water-lipid hydrogen bonding, as it occurs at bilayer separations where water-lipid hydrogen bonds become more common than water-water hydrogen bonds. We further show that such coupling occurs in simulations of vesicle-vesicle fusion prior to the fusion event itself. Such altered dynamics at membrane-membrane interfaces may both stabilize the interfacial contact and slow fusion stalk formation within the interface region.
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http://dx.doi.org/10.1021/ja508803d | DOI Listing |
Stem Cell Res Ther
January 2025
Department of Orthopedics, Faculty of Medicine, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran.
Exosomes are small extracellular vesicles of endocytic origin released by various cell types. They consist of lipid bilayers containing macromolecules such as lipids, proteins, microRNAs, growth factors, cytokines, and carbohydrates. Exosomes play a critical role in the diagnosis and treatment of various diseases.
View Article and Find Full Text PDFJ Phys Chem B
January 2025
Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk 630090, Russia.
Plasma membranes are known to segregate into liquid disordered and ordered nanoscale phases, the latter being called lipid rafts. The structure, lipid composition, and function of lipid rafts have been the subject of numerous studies using a variety of experimental and computational methods. Double electron-electron resonance (DEER, also known as PELDOR) is a member of the pulsed dipole EPR spectroscopy (PDS) family of techniques, allowing the study of nanoscale distances between spin-labeled molecules.
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December 2024
Faculty of Chemistry, Biological and Chemical Research Centre, University of Warsaw, ul. Zwirki i Wigury 101, 02-089 Warsaw, Poland.
In this study, we explore the interactions between melittin, a cationic antimicrobial peptide, and model lipid membranes composed of the negatively charged phospholipids 1,2-dimyristoyl-sn-glycero-3-phosphoglycerol (DMPG) and 1,2-dimyristoyl-sn-glycero-3-phosphoserine (DMPS). Using the Langmuir monolayer technique and atomic force microscopy (AFM), we reveal novel insights into these interactions. Our key finding is the observation of the ripple phase in the DMPS bilayer on mica, a phenomenon not previously reported for negatively charged single bilayers.
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December 2024
REQUIMTE, LAQV, Instituto de Ciências Biomédicas de Abel Salazar, Universidade do Porto, Rua Jorge Viterbo Ferreira, 228, 4050-313 Porto, Portugal.
In this study, we synthesized a series of 3-hydroxy-4-pyridinone (3,4-HPO) chelators with varying lipophilicity by modifying the length of their alkyl chains. To investigate their interaction with lipid membranes, we employed differential scanning calorimetry (DSC) and electron paramagnetic resonance (EPR) spectroscopy using dimyristoylphosphatidylcholine (DMPC) and palmitoyloleoylphosphatidylcholine (POPC) liposomes as membrane model systems. DSC experiments on DMPC liposomes revealed that hexyl-substituted chelators significantly altered the thermotropic phase behavior of the lipid bilayer, indicating their potential as membrane property modulators.
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December 2024
Coimbra Chemistry Center, Institute of Molecular Sciences (CQC-IMS), University of Coimbra, 3004-535 Coimbra, Portugal.
The membrane dipole potential that arises from the interfacial water and constitutive dipolar groups of lipid molecules modulates the interaction of amphiphiles and proteins with membranes. Consequently, its determination for lipid mixtures resembling the existing diversity in biological membranes is very relevant. In this work, the dipole potentials of monolayers, formed at the air-water interface, from pure or mixed lipids (1-palmitoyl-2-oleoyl--glycero-3-phosphocholine (POPC), 1-palmitoyl-2-oleoyl--glycero-3-phosphoethanolamine (POPE), 1-palmitoyl-2-oleoyl--glycero-3-phosphatidyserine (POPS), sphingomyelin (SpM) and cholesterol) were measured and correlated with the mean area per lipid.
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