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Analytical Chemistry Aug 2023Lipid membranes are crucial for cellular integrity and regulation, and tight control of their structural and mechanical properties is vital to ensure that they function...
Lipid membranes are crucial for cellular integrity and regulation, and tight control of their structural and mechanical properties is vital to ensure that they function properly. Fluorescent probes sensitive to the membrane's microenvironment are useful for investigating lipid membrane properties; however, there is currently a lack of quantitative correlation between the exact parameters of lipid organization and a readout from these dyes. Here, we investigate this relationship for "molecular rotors", or microviscosity sensors, by simultaneously measuring their fluorescence lifetime to determine the membrane viscosity, while using X-ray diffraction to determine the membrane's structural properties. Our results reveal a phase-dependent correlation between the membrane's structural parameters and mechanical properties measured by a BODIPY-based molecular rotor, giving excellent predictive power for the structural descriptors of the lipid bilayer. We also demonstrate that differences in membrane thickness between different lipid phases are not a prerequisite for the formation of lipid microdomains and that this requirement can be disrupted by the presence of line-active molecules. Our results underpin the use of membrane-sensitive dyes as reporters of the structure of lipid membranes.
Topics: Lipid Bilayers; Viscosity; Fluorescent Dyes; Membranes; Fluorescence; Cell Membrane
PubMed: 37526607
DOI: 10.1021/acs.analchem.3c01747 -
Analytical Chemistry Aug 2022Measurement of protein-facilitated copper flux across biological membranes is a considerable challenge. Here, we demonstrate a straightforward microfluidic-derived...
Measurement of protein-facilitated copper flux across biological membranes is a considerable challenge. Here, we demonstrate a straightforward microfluidic-derived approach for visualization and measurement of membranous Cu flux. Giant unilamellar vesicles, reconstituted with the membrane protein of interest, are prepared, surface-immobilized, and assessed using a novel quencher-sensor reporter system for detection of copper. With the aid of a syringe pump, the external buffer is exchanged, enabling consistent and precise exchange of solutes, without causing vesicle rupture or uneven local metal concentrations brought about by rapid mixing. This approach bypasses common issues encountered when studying heavy metal-ion flux, thereby providing a new platform for studies of metal homeostasis aspects that are critical for all cells, health, and disease.
Topics: Copper; Lipids; Membranes; Microfluidics; Proteins; Unilamellar Liposomes
PubMed: 35969432
DOI: 10.1021/acs.analchem.2c02081 -
Sensors (Basel, Switzerland) 2010This review examines some recent applications of fluorescence recovery after photobleaching (FRAP) to biopolymers, while mainly focusing on membrane protein studies.... (Review)
Review
This review examines some recent applications of fluorescence recovery after photobleaching (FRAP) to biopolymers, while mainly focusing on membrane protein studies. Initially, we discuss the lateral diffusion of membrane proteins, as measured by FRAP. Then, we talk about the use of FRAP to probe interactions between membrane proteins by obtaining fundamental information such as geometry and stoichiometry of the interacting complex. Afterwards, we discuss some applications of FRAP at the cellular level as well as the level of organisms. We conclude by comparing diffusion coefficients obtained by FRAP and several other alternative methods.
Topics: Animals; Fluorescence Recovery After Photobleaching; Humans; Macromolecular Substances; Membrane Proteins; Membranes; Models, Biological; Models, Theoretical
PubMed: 22219695
DOI: 10.3390/s100605927 -
FEBS Letters Oct 1989It is shown that investigating the lateral motion of lipids in biological membranes can provide useful information on membrane lateral organization. After labeling... (Review)
Review
It is shown that investigating the lateral motion of lipids in biological membranes can provide useful information on membrane lateral organization. After labeling membranes with extrinsic or intrinsic lipophilic fluorescent probes, fluorescence recovery after photobleaching experiments strongly suggests that specialized cells like spermatozoa, eggs and epithelia exhibit surface membrane regionalization or macrocompartmentation and that lateral microheterogeneities or lipid microdomains exist in the plasma membrane of many cellular systems.
Topics: Animals; Diffusion; Membrane Lipids; Membranes
PubMed: 2680602
DOI: 10.1016/0014-5793(89)81774-0 -
Chinese Journal of Traumatology =... Jun 2011To study the anatomical and biomechanical features of the interosseous membrane (IOM) of the cadaveric forearm.
OBJECTIVE
To study the anatomical and biomechanical features of the interosseous membrane (IOM) of the cadaveric forearm.
METHODS
Ten radius-IOM-ulna structures were harvested from fresh-frozen cadavers to measure the length, width and thickness of the tendinous portion of IOM. Then, the tendinous portion was isolated along with the ulnar and radial ends to which the tendon attached after measurement. The proximal portion of the radius and the distal portion of the ulna were embedded and fixed in the dental base acrylic resin powder. The embedded specimen was clamped and fixed by the MTS 858 test machine using a 10 000 N load cell for the entire tensile test. IOM was stretched at a speed of 50 mm/min until it was ruptured. The load-displacement curve was depicted with a computer and the maximum load and stiffness were recorded at the same time.
RESULTS
The IOM of the forearm was composed of three portions: central tendinous tissue, membranous tissue and dorsal affiliated oblique cord. IOM was stretched at a neutral position, and flexed at pronation and supination positions. The tendinous portion of IOM was lacerated in 6 specimens when the point of the maximum load reached to 1021.50 N+/-250.13 N, the stiffness to 138.24 N/m+/-24.29 N/m, and the length of stretch to 9.77 mm+/-1.77 mm. Fracture occurred at the fixed end of the ulna before laceration of the tendinous portion in 4 specimens when the maximum load was 744.40 N+/-109.85 N, the stiffness was 151.17 N/m+/-30.68 N/m, and the length of the stretch was 6.51 mm+/-0.51 mm.
CONCLUSIONS
The IOM of the forearm is a structure having ligamentous characteristics between the radius and the ulna. It is very important for maintenance of the longitudinal stability of the forearm. The anatomical and biomechanical data can be used as an objective criterion for evaluating the reconstructive method of IOM of the forearm.
Topics: Biomechanical Phenomena; Cadaver; Forearm; Humans; Membranes; Radius; Ulna
PubMed: 21635800
DOI: No ID Found -
Archaea (Vancouver, B.C.) 2012This paper reviews the recent findings related to the physical properties of tetraether lipid membranes, with special attention to the effects of the number, position,... (Review)
Review
This paper reviews the recent findings related to the physical properties of tetraether lipid membranes, with special attention to the effects of the number, position, and configuration of cyclopentane rings on membrane properties. We discuss the findings obtained from liposomes and monolayers, composed of naturally occurring archaeal tetraether lipids and synthetic tetraethers as well as the results from computer simulations. It appears that the number, position, and stereochemistry of cyclopentane rings in the dibiphytanyl chains of tetraether lipids have significant influence on packing tightness, lipid conformation, membrane thickness and organization, and headgroup hydration/orientation.
Topics: Cyclopentanes; Lipids; Liposomes; Membranes; Molecular Structure
PubMed: 23028246
DOI: 10.1155/2012/138439 -
Biochimica Et Biophysica Acta.... Jan 2023The fusion between two lipid membranes is a ubiquitous mechanism in cell traffic and pathogens invasion. Yet it is not well understood how two distinct bilayers overcome...
The fusion between two lipid membranes is a ubiquitous mechanism in cell traffic and pathogens invasion. Yet it is not well understood how two distinct bilayers overcome the energy barriers towards fusion and reorganize themselves to form a unique continuous bilayer. The magnitudes and numbers of these energy barriers are themselves an open question. To tackle these issues, we developed a new tool that allows to control the forces applied between two supported lipid bilayers (SLBs) deposited on superparamagnetic beads. By applying a magnetic field, the beads self-organize along field lines in chains of beads and compress the two membranes on the contact zone. Using the diffusion of fluorescently labelled lipids from one bilayer to the other allows us to identify fusion of the bilayers in contact. We applied increasing forces on SLBs and increased the occurrence of fusion. This experimental system allows the simultaneous study of tens of facing bilayers in a single experiment and mitigates the stochasticity of the fusion process. It is thus a powerful tool to test the various parameters involved in the membrane fusion process.
Topics: Lipid Bilayers; Membrane Fusion; Diffusion; Membranes; Magnetic Iron Oxide Nanoparticles
PubMed: 36220376
DOI: 10.1016/j.bbamem.2022.184070 -
The Journal of Cell Biology May 1963Peak-to-peak distances between two dense lines of the unit membranes of cell organelles were measured on electron micrographs. These distances were compared with...
Peak-to-peak distances between two dense lines of the unit membranes of cell organelles were measured on electron micrographs. These distances were compared with corresponding measurements on the plasma membrane and assigned a percentage value. The comparison between organelle and plasma membrane was always carried out with the same negative, in order to exclude as far as possible errors due to differences in focus or other causes. It was revealed by this study that the membranous structures of the cell can be classified into two groups, one thicker and one thinner. Unit membranes of the thicker group (synaptic vesicles, vesicles and capsules of multivesicular bodies, Golgi vesicles) were not significantly different in thickness from the plasma membrane. Unit membranes of the thinner group (mitochondria, nuclear membranes, Golgi lamellae, endoplasmic reticulum), however, were between 85 and 90 per cent of the thickness of the plasma membrane.
Topics: Animals; Cell Biology; Cell Membrane; Electrons; Endoplasmic Reticulum; Golgi Apparatus; Membranes; Microscopy; Microscopy, Electron; Mitochondria; Nuclear Envelope; Organelles
PubMed: 14002339
DOI: 10.1083/jcb.17.2.413 -
Scientific Reports Aug 2017Allogeneic islet transplantation into the liver in combination with immune suppressive drug therapy is widely regarded as a potential cure for type 1 diabetes. However,...
Allogeneic islet transplantation into the liver in combination with immune suppressive drug therapy is widely regarded as a potential cure for type 1 diabetes. However, the intrahepatic system is suboptimal as the concentration of drugs and nutrients there is higher compared to pancreas, which negatively affects islet function. Islet encapsulation within semipermeable membranes is a promising strategy that allows for the islet transplantation outside the suboptimal liver portal system and provides environment, where islets can perform their endocrine function. In this study, we develop a macroencapsulation device based on thin microwell membranes. The islets are seeded in separate microwells to avoid aggregation, whereas the membrane porosity is tailored to achieve sufficient transport of nutrients, glucose and insulin. The non-degradable, microwell membranes are composed of poly (ether sulfone)/polyvinylpyrrolidone and manufactured via phase separation micro molding. Our results show that the device prevents aggregation and preserves the islet's native morphology. Moreover, the encapsulated islets maintain their glucose responsiveness and function after 7 days of culture (stimulation index above 2 for high glucose stimulation), demonstrating the potential of this novel device for islet transplantation.
Topics: Animals; Biocompatible Materials; Biological Transport; Cell Line; Cell Survival; Diabetes Mellitus, Type 1; Glucose; Humans; Insulin; Islets of Langerhans; Islets of Langerhans Transplantation; Membranes; Mice; Permeability; Porosity; Tissue Culture Techniques; Tissue Scaffolds
PubMed: 28835662
DOI: 10.1038/s41598-017-09647-7 -
Biophysical Journal Dec 2021Despite their wide applications in soluble macromolecules, optical tweezers have rarely been used to characterize the dynamics of membrane proteins, mainly due to the...
Despite their wide applications in soluble macromolecules, optical tweezers have rarely been used to characterize the dynamics of membrane proteins, mainly due to the lack of model membranes compatible with optical trapping. Here, we examined optical trapping and mechanical properties of two potential model membranes, giant and small unilamellar vesicles (GUVs and SUVs, respectively) for studies of membrane protein dynamics. We found that optical tweezers can stably trap GUVs containing iodixanol with controlled membrane tension. The trapped GUVs with high membrane tension can serve as a force sensor to accurately detect reversible folding of a DNA hairpin or membrane binding of synaptotagmin-1 C2AB domain attached to the GUV. We also observed that SUVs are rigid enough to resist large pulling forces and are suitable for detecting protein conformational changes induced by force. Our methodologies may facilitate single-molecule manipulation studies of membrane proteins using optical tweezers.
Topics: Macromolecular Substances; Membrane Proteins; Membranes; Optical Tweezers; Unilamellar Liposomes
PubMed: 34813728
DOI: 10.1016/j.bpj.2021.11.2884