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. In the paper, the bending rigidity coefficient was measured using the fluorescence-enhanced flicker-noise spectroscopy. In the paper, the bending rigidity coefficient was determined for large populations of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphocholine vesicles. The quantity of obtained experimental data allows to perform statistical analysis aiming at the identification of the distribution, which is the most appropriate for the calculation of the value of the membrane bending rigidity coefficient. It has been demonstrated that the bending rigidity coefficient is characterized by an asymmetrical distribution, which is well approximated with the gamma distribution. Since there are no biophysical reasons for that we propose to use the difference between normal and gamma fits as a measure of the homogeneity of vesicle population. In addition, the effect of a fluorescent label and types of instrumental setups on determined values has been tested. Obtained results show that the value of the bending rigidity coefficient does not depend on the type of a fluorescent label nor on the type of microscope used.
Studies on the deformation behaviours of cellular entities, such as coated microbubbles and liposomes subject to a cavitation flow, become increasingly important for the advancement of ultrasonic ...imaging and drug delivery. Numerical simulations for bubble dynamics of ultrasound contrast agents based on the boundary integral method are presented in this work. The effects of the encapsulating shell are estimated by adapting Hoff's model used for thin-shell contrast agents. The viscosity effects are estimated by including the normal viscous stress in the boundary condition. In parallel, mechanical models of cell membranes and liposomes as well as state-of-the-art techniques for quantitative measurement of viscoelasticity for a single cell or coated microbubbles are reviewed. The future developments regarding modelling and measurement of the material properties of the cellular entities for cutting-edge biomedical applications are also discussed.
A two-dimensional model for red blood cell motion is adapted to consider the dynamics of breast cancer cells in a microfluidic channel. Adjusting parameters to make the membrane stiffer, as is the ...case with breast cancer cells compared with red blood cells, allows the model to produce reasonable estimates of breast cancer cell trajectories through the channel. In addition, the model produces estimates of quantities not as easily obtained from experiment such as velocity and stress field information throughout the fluid and on the cell membrane. This includes locations of maximum stress along the membrane wall. A sensitivity analysis shows that the model is capable of producing useful insights into various systems involving breast cancer cells. Current results suggest that dynamics taking place when cells are near other objects are most sensitive to membrane and cytoplasm elasticity, dynamics taking place when cells are not near other objects are most sensitive to cytoplasm viscosity, and dynamics are significantly affected by low membrane bending elasticity. These results suggest that continued calibration and application of this model can yield useful predictions in other similar systems.
Locusts display a striking form of phenotypic plasticity, developing into either a lone-living solitarious phase or a swarming gregarious phase depending on population density. The two phases differ ...extensively in appearance, behaviour and physiology. We found that solitarious and gregarious locusts have clear differences in their hearing, both in their tympanal and neuronal responses. We identified significant differences in the shape of the tympana that may be responsible for the variations in hearing between locust phases. We measured the nanometre mechanical responses of the ear's tympanal membrane to sound, finding that solitarious animals exhibit greater displacement. Finally, neural experiments signified that solitarious locusts have a relatively stronger response to high frequencies. The enhanced response to high-frequency sounds in the nocturnally flying solitarious locusts suggests greater investment in detecting the ultrasonic echolocation calls of bats, to which they are more vulnerable than diurnally active gregarious locusts. This study highlights the importance of epigenetic effects set forth during development and begins to identify how animals are equipped to match their immediate environmental needs.
Membrane proteins are essential for the diverse biological functions of the cells and intercellular communication in living organisms. With the recent developments in the methodologies, the research ...on membrane proteins has been undergoing a major transformation. In this informative book, the biological and dynamic behaviour of membrane proteins are introduced, discussed, and reviewed by some of the leading researchers in the field. The main objective of this compendium is to present the recent research in the fundamental and advanced concepts and methodologies used for studying membrane proteins. Membrane protein purification and reconstitution, protein–lipid interaction, ion/substrate transport, conformational and functional dynamics, the interaction of infectious agents, cell death, and organelle morphology are among the topics that are covered. This reprint is intended for a broad range of novice and experienced scientists with different levels of experience, from biophysicists and biochemists to microbiologists, cell biologists, and physiologists.
We demonstrate here that triolein alters the mechanical properties of phospholipid membranes and induces extraordinary conformational dynamics. Triolein containing membranes exhibit fluctuations up ...to size range of 100
μm and with the help of these are e.g. able to squeeze through narrow passages between neighbouring structures. Triolein–phosphatidylcholine membranes were found to have bending rigidity significantly lower than that of corresponding pure phosphatidylcholine membrane. Moreover, the triolein containing membranes were found to be reluctant to fuse, which is in good accordance with larger lamellar distances observed in the TOPOPC membranes. These findings suggest repulsion between adjacent membranes. We provide a comprehensive discussion on the possible explanations for the observed mechanics and dynamics in the TOPOPC system and on their potential cellular implications.
► Triolein induces unique mechanics and dynamics in PC membranes. ► Shape dynamics and structure formation of membranes with triolein are altered. ► Bending elasticity of the membrane is significantly lowered by triolein. ► The observed membrane alterations may have significance for cell plasma membranes.
Tagging living cells with magnetic nanoparticles raised increasing interest in the fields of magnetic resonance imaging, magnetic hyperthermia, cell sorting or tissue engineering. Here, we ...demonstrate that the confinement of magnetic nanoparticles at the intracellular level, inside endosomes vesicles, allows developing original magnetic manipulations in response to different magnetic field solicitations. These manipulations are used to deform cellular internal membrane, to probe the cell architecture or to heat the cell from its inside.
Magainin 2 belongs to the family of peptides, which interacts with the lipid membranes. The present work deals with the effect of this peptide on the mechanical properties of 1-palmitoyl-2-oleoyl-
...sn-glycerol-3-phosphocholine Giant Unilamellar Vesicle, characterized by the bending stiffness modulus. The bending elastic modulus is measured by Vesicle Fluctuation Analysis at biologically relevant pH and physiological buffer conditions and shows a dramatic decrease with increasing peptide concentration. The observed bilayer softening is interpreted in terms of a continuum model describing perturbations on the membrane organization. Our analysis suggests that the adsorbed peptides give rise to considerable local curvature disruptions of the membrane.
Abstract Flow-induced membrane tension contributes to the release of molecules by red blood cells (RBCs), and extremely high tension may cause haemolysis. Here, we investigated the membrane tension ...of RBCs during pairwise interactions in simple shear flow, given that pairwise interactions form the basis of many-body interactions. RBCs were modelled as capsules with a two-dimensional hyperelastic membrane, and large deformations were solved by the finite element method. Due to the small size of the RBCs, surrounding fluid motion was estimated as a Stokes flow and solved by the boundary element method. The results showed that the maximum isotropic tension appeared around the dimple of the biconcave surface and not around the rim. A comparison of the results with solitary cases indicated that the maximum principal tension and isotropic tension were significantly increased by cell–cell interaction effects. As the volume fraction of RBCs is large under physiological conditions, as well as in blood flow in vitro, cell–cell interactions must be analysed carefully when considering mechanotransduction and haemolysis in blood flow.
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