Proton diffusion on the surface of mixed lipid membranes highlights the role of membrane composition.

Proton circuits within biological membranes, the foundation of natural bioenergetic systems, are significantly influenced by the lipid compositions of different biological membranes. In this study, we investigate the influence of mixed lipid membrane composition on the proton transfer (PT) properties on the surface of the membrane. We track the excited-state PT (ESPT) process from a tethered probe to the membrane with timescales and length scales of PT relevant to bioenergetic systems.

Effect of leaflet asymmetry on the stretching elasticity of lipid bilayers with phosphatidic acid.

The asymmetry of membranes has a significant impact on their biophysical characteristics and behavior. This study investigates the composition and mechanical properties of symmetric and asymmetric membranes in giant unilamellar vesicles (GUVs) made of palmitoyloleoyl phosphatidylcholine (POPC) and palmitoyloleoyl phosphatidic acid (POPA). A combination of fluorescence quantification, zeta potential measurements, micropipette aspiration, and bilayer molecular dynamics simulations are used to characterize these membranes.

Multifaceted Activity of Fabimycin: Insights from Molecular Dynamics Studies on Bacterial Membrane Models.

Membranes─cells' essential scaffolds─are valid molecular targets for substances with an antimicrobial effect. While certain substances, such as octenidine, have been developed to target membranes for antimicrobial purposes, the recently reported molecule, fabimycin (F2B)─a novel agent targeting drug-resistant Gram-negative bacteria─has not received adequate attention regarding its activity on membranes in the literature. The following study aims to investigate the effects of F2B on different bacterial membrane models, including simple planar bilayers and more complex bilayer systems that mimic the shell equipped with double inner and outer bilayers.

Investigation of nano- and microdomains formed by ceramide 1 phosphate in lipid bilayers.

Biological membranes are renowned for their intricate complexity, with the formation of membrane domains being pivotal to the successful execution of numerous cellular processes. However, due to their nanoscale characteristics, these domains are often understudied, as the experimental techniques required for quantitative investigation present significant challenges. In this study we employ spot-variation z-scan fluorescence correlation spectroscopy (svzFCS) tailored for artificial lipid vesicles of varying composition and combine this approach with high-resolution imaging.

Bioavailability by design - Vitamin D liposomal delivery vehicles.

Vitamin D3 deficiency has serious health consequences, as demonstrated by its effect on severity and recovery after COVID-19 infection. Because of high hydrophobicity, its absorption and subsequent redistribution throughout the body are inherently dependent on the accompanying lipids and/or proteins. The effective oral vitamin D formulation should ensure penetration of the mucus layer followed by internalization by competent cells.

Simple Does Not Mean Trivial: Behavior of Phosphatidic Acid in Lipid Mono- and Bilayers.

Phosphatidic acid (PA) is one of the simplest membrane phospholipids, yet it plays a crucial role in various biologically relevant processes that take place in cells. Since PA generation may be triggered by a variety of factors, very often of antagonistic character, the specific nature of physiological responses driven by PA is not clear. In order to shed more light on these issues, we carried out a systematic characterization of membranes containing one of the three biologically significant PA molecular species.

The Effect of the Osmotically Active Compound Concentration Difference on the Passive Water and Proton Fluxes across a Lipid Bilayer.

The molecular details of the passive water flux across the hydrophobic membrane interior are still a matter of debate. One of the postulated mechanisms is the spontaneous, water-filled pore opening, which facilitates the hydrophilic connection between aqueous phases separated by the membrane. In the paper, we provide experimental evidence showing that the spontaneous lipid pore formation correlates with the membrane mechanics; hence, it depends on the composition of the lipid bilayer and the concentration of the osmotically active compound.

A Systematic Approach: Molecular Dynamics Study and Parametrisation of Gemini Type Cationic Surfactants.

The spreading of antibiotic-resistant bacteria strains is one of the most serious problem in medicine to struggle nowadays. This triggered the development of alternative antimicrobial agents in recent years. One of such group is Gemini surfactants which are massively synthesised in various structural configurations to obtain the most effective antibacterial properties.

Molecular characterization of direct interactions between MPP1 and flotillins.

Flotillins are the major structural proteins in erythroid raft domains. We have shown previously that the dynamic nanoscale organization of raft domains in erythroid cells may depend on flotillin-MPP1 interactions. Here, by using molecular dynamic simulations and a surface plasmon resonance-based approach we determined that high-affinity complexes of MPP1 and flotillins are formed via a so far unidentified region within the D5 domain of MPP1.

Unraveling the mechanism of octenidine and chlorhexidine on membranes: Does electrostatics matter?

The increasing problem of antibiotic resistance in bacteria requires the development of new antimicrobial candidates. There are several well-known substances with commercial use, but their molecular mode of action is not fully understood. In this work, we focus on two commonly used antimicrobial agents from the detergent family-octenidine dichloride (OCT) and chlorhexidine digluconate (CHX).

Effect of Amyloid-β Monomers on Lipid Membrane Mechanical Parameters-Potential Implications for Mechanically Driven Neurodegeneration in Alzheimer's Disease.

Alzheimer's disease (AD) is a neurodegenerative disease that results in memory loss and the impairment of cognitive skills. Several mechanisms of AD's pathogenesis were proposed, such as the progressive accumulation of amyloid-β (Aβ) and τ pathology. Nevertheless, the exact neurodegenerative mechanism of the Aβ remains complex and not fully understood.

Determination of the Mechanical Properties of Model Lipid Bilayers Using Atomic Force Microscopy Indentation.

By conducting a systematic study of model lipid membranes using the atomic force microscopy (AFM) indentation, we demonstrate the importance of an experimental protocol on the determination of their mechanical parameters. We refine the experimental approach by analyzing the influence of the contact mechanics models used to process the data, substrate preparation, and indenter geometry. We show that both bending rigidity and area compressibility can be determined from a single AFM indentation measurement.

Mechanical Properties Determination of DMPC, DPPC, DSPC, and HSPC Solid-Ordered Bilayers.

Lipid bilayers are active participants in many crucial biological processes. They can be observed in different phases, liquid and solid, respectively. The liquid phase is predominant in biological systems.

Statistical Analysis of Bending Rigidity Coefficient Determined Using Fluorescence-Based Flicker-Noise Spectroscopy.

Bending rigidity coefficient describes propensity of a lipid bilayer to deform. In order to measure the parameter experimentally using flickering noise spectroscopy, the microscopic imaging is required, which necessitates the application of giant unilamellar vesicles (GUV) lipid bilayer model. The major difficulty associated with the application of the model is the statistical character of GUV population with respect to their size and the homogeneity of lipid bilayer composition, if a mixture of lipids is used.

Effects of electroformation protocol parameters on quality of homogeneous GUV populations.

Giant unilamellar vesicles (GUVs) have become one of extensively studied biological bilayer models especially when investigating topological and mechanical properties of cell membranes. They are also used to visualize membrane-related phenomena. However, the method of preparation and the effects of parameters of preparation on the vesicular structure are extensively varied.

Alterations of biomechanics in cancer and normal cells induced by doxorubicin.

Mechanical properties of biological structures play an important role in regulating cellular activities and are critical for understanding metabolic processes in cancerous cells and the effects of drugs. For some cancers, such as acute myeloid leukaemia, chemotherapy is one of preferential methods. However, due to the lack of selectivity to cancer cells, cytostatic agents cause toxicity to normal tissues.

Changes in lipid membrane mechanics induced by di- and tri-phenyltins.

Organotin compounds, being biologically active, affect a variety of cellular functions due to their ability to accumulate in and penetrate biological membranes. These compounds influence the distribution of electrostatic charges, alter organization, disrupt molecular dynamics and change mechanical properties of biological membranes. It was found that the membrane/water partition coefficient equals 4, a value significantly higher than octanol/water partition coefficient.

The Effect of a Fluorophore Photo-Physics on the Lipid Vesicle Diffusion Coefficient Studied by Fluorescence Correlation Spectroscopy.

Fluorescence Correlation Spectroscopy (FCS) is a technique, which allows determination of the diffusion coefficient and concentration of fluorescent objects suspended in the solution. The measured parameter is the fluctuation of the fluorescence signal emitted by diffusing molecules. When 100 nm DOPC vesicles labeled with various fluorescent dyes (Fluorescein-PE, NBD-PE, Atto488 DOPE or βBodipy FL) were measured, different values of diffusion coefficients have been obtained.

The modified fluorescence based vesicle fluctuation spectroscopy technique for determination of lipid bilayer bending properties.

Lipid bilayer is the main constitutive element of biological membrane, which confines intracellular space. The mechanical properties of biological membranes may be characterized by various parameters including membrane stiffness or membrane bending rigidity, which can be measured using flicker noise spectroscopy. The flicker noise spectroscopy exploits the spontaneous thermal undulations of the membrane.

A molecular dynamics study of catestatin docked on nicotinic acetylcholine receptors to identify amino acids potentially involved in the binding of chromogranin A fragments.

Catestatin, a cationic and hydrophobic 21-amino acid fragment of chromogranin A, is known to be a non-competitive nicotinic antagonist acting through nicotinic acetylcholine receptors (nAChRs) to inhibit catecholamine release. Since this receptor is the target of several neuronal and non-neuronal disorder prophylaxes and treatments, this study aims at the elucidation of the binding of human catestatin to the entire nAChR reconstructed in lipid bilayers by means of docking followed by full atomistic molecular dynamics simulations. The obtained results show that the minimum free energy for the binding of the peptide and the receptor attains minimal values for locations at the pore site and in the outer beta subunit.

Effect of monovalent anions on water transmembrane transport.

Biological structures consist of lipid bilayers immersed in the aqueous phase. They can be considered as a two-phase system where the two phases are separated (connected) by the transition regions (interphases), which properties are affected by both lipid and aqueous phases. Interphase structure and dynamics might influence properties and/or functioning of the lipid bilayer core, including osmotically induced water flow.