Bilayer lipid membranes , membrane transport

II. VOLTAMMETRIC ELUCIDATION OF THE CHARGE TRANSPORT PROCESS THROUGH A LIQUID MEMBRANE OR A BILAYER LIPID MEMBRANE IN THE PRESENCE OF SUFFICIENT ELECTROLYTES [10,17,18]... 

Antonenko, Y. N. Denisov, G. A. Pohl, P., Weak acid transport across bilayer lipid membrane in the presence of buffers, Biophys. J. 64, 1701-1710 (1993). 

A solution of brain lipids was brushed across a small hole in a 5-ml. polyethylene pH cup immersed in an electrolyte solution. As observed under low power magnification, the thick lipid film initially formed exhibited intense interference colors. Finally, after thinning, black spots of poor reflectivity suddenly appeared in the film. The black spots grew rapidly and evenutally extended to the limit of the opening (5, 10). The black membranes have a thickness ranging from 60-90 A. under the electron microscope. Optical and electrical capacitance measurements have also demonstrated that the membrane, when in the final black state, corresponds closely to a bimolecular leaflet structure. Hence, these membranous structures are known as bimolecular, black, or bilayer lipid membranes (abbreviated as BLM). The transverse electrical and transport properties of BLM have been studied usually by forming such a structure interposed between two aqueous phases (10, 17). 

Mironov SL, Sokolov Y, Chanturiya AN et al (1986) Channels produced by spider venoms in bilayer lipid membrane mechanisms of ion transport and toxic action. Biochim Biophys Acta 862 185-98... 

The transport of molecules across biological cell membranes and biomimetic membranes, including planar bilayer lipid membranes (BLMs) and giant liposomes, has been studied by SECM. The approaches used in those studies are conceptually similar to generation-collection and feedback SECM experiments. In the former mode, an amperometric tip is used to measure concentration profiles and monitor fluxes of molecules crossing the membrane. In a feedback-type experiment, the tip process depletes the concentration of the transferred species on one side of the membrane and in this way induces its transfer across the membrane. 

As described above, the ion transfer through a membrane is controlled practically by the complementary ion transfer reactions at two W/M interfaces when the M contained sufficient electrolytes. This idea was successfully applied to explanations of the following subjects concerning with membrane phenomena [20,21,26]. (1) Influence of ion transfer reaction at one W/M interface on that at another W/M interface under an applied membrane potential (2) Ion transfers through an M in the presence of the objective ion in Wl, M and/or W2 (3) Ion separation by electrolysis under an applied membrane potential (4) Ion transfer through a thin supported liquid membrane. The idea was also demonstrated to be very useful for the elucidation of ion or electron transport process through a bilayer lipid membrane (BLM), which is much thinner than a liquid membrane [21,26]. 

Ion transfer across phospholipid monolayers at liquid-liquid interfaces has been studied with the aim of elucidating the mechanism and kinetics of ion transport across a bilayer lipid membrane (BLM). The main advantage of using these systems is in the possibility of controlling the interfacial potential difference, which in the case of the BLM has to be inferred indirectly [141]. 

Biological cell membranes are multi-component systems consisting of a fluid bilayer lipid membrane (BLM) and integrated membrane proteins. The main structural features of the BLMs are determined by a wide variety of amphiphilic lipids whose polar head groups are exposed to water while hydrocarbon tails form the nonpolar interior. The BLMs act as the medium for biochemical vectorial membrane processes such as photosynthesis, respiration and active ion transport. However, they do not participate in the corresponding chemical reactions which occur in membrane-dissolved proteins and often need redox-active cofactors. BLMs were therefore mostly investigated by physical chemists who studied their thermodynamics and kinetic behaviour . ... 

Figure 7. Sugar permeability plot for bilayer lipid membrane (egg lecithin-cholesterol in n-decane) at 25 °C. The slope of the plot before and after addition of extract is equal to the permeability coefficient. Passive diffusion of D-[ C]glucose (O) and facilitated diffusion ( ) on addition of band 4.5 (sugar transporter) at a concentration of 0.99 (Jig cm to the trans side of the bilayer. (Reproduced with permission from Ref. 44. Copyright 1982 Elsevier Science.)...

Ion-Transport Processes Through Membranes of Various Types Liquid Membrane, Thin Supported Liquid Membrane, and Bilayer Lipid Membrane Osamu Shirai and Sorin Kihara... 

The ion-transport process through a bilayer lipid membrane (BLM), which is much thinner than an LM, was also explained on the basis of ion-transfer reactions at the aqueous/BLM interface [17,18]. 

The electron in the electron transport chain is not free like in a metal wire. Therefore the electron motion in each act involves surmounting an energy barrier. As was shown in Refs. 16 and 108-110, a substantial role in this process is played by the conformations of the macromolecular components of the electron transport chain. Nevertheless, the simplest model systems of electron transport realized on bilayer lipid membranes were virtually based on the concept of a membrane as a thin liquid hydrocarbon in which a substance capable of redox transformations is dissolved, the products of this reaction being able to diffuse inside the bilayer. The electron transport from the aqueous phase containing a reducer amounts to injection of charges into the nonaqueous phase if it contains an electron acceptor ... 

The considerable advance achieved in recent years in the discrete treatment of transport processes is primarily due to the development of the bilayer lipid membranes (BLM) modifiable with various ionophores. The most important results directly concerned with the functioning of excitable membranes are highlighted in Sections 4.2 and 4.3. 

Silane modification of ITO and Sn02 electrodes has also heen used to create nearly perfect blocking electrodes, such as thin films where rates of electron transfer are intentionally kept low, so as to provide for measurement in changes in interfacial potential of an additional overlayer, such as a bilayer lipid membrane, during ion transport, pH changes, and so forth. Hdlebrandt and Tanaka have evaluated the effects of octyltrimethoxysilane (OTMS), octadecyltrimethoxysilane (ODTMS), and octadecyltrichlorosilane (OTS) on ITO for applications to lipid-membrane-based... 

Lipid bilayers having a thickness of around 5 ran were probably the earliest nanoscale systems studied by potentiometry. Although initially the research was motivated by the understanding of ion transport through biological membranes, some potentiometric studies are also available. Mueller and coworkers pioneered the preparation of planar bilayer lipid membranes (BLMs) having a diameter of about 1 mm. Such membranes, which are spontaneously formed from a solution of lipids,... 

Grime, J. M. A., Edwards, M. A., Rudd, N. C., Unwin, P. R. Quantitative visualization of passive transport across bilayer lipid membranes. Proc. Natl. Acad. Set USA 2008, 105, 14277. 

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