Membrane bimolecular

Montal, M., and P. Mueller, Formation of bimolecular membranes from lipid monolayers and a study of their electrical properties, Proc. Natl. Acad. Sci. USA, 69, 3561 (1972). 

Table I. Bifacial Tension0 of Some Bimolecular Membranes at 25°C.

Relation to Other Studies. Interaction of Ca++ with phosphatidyl choline (PC) mono- and bimolecular membranes has been investigated carefully by Hauser and Phillips (15) and McLaughlin (17). Using a variety of approaches such as AV, surface radioactivity, zeta potential measurements, and NMR studies, both groups of investigators concluded that Ca++ interacts with the phosphate residues of lecithin the extent of the interaction, however, is very small since it involves less than 5% of the phosphate residues (17). 

Phospholipids are amphipathic molecules, that is, they have parts of different polarity. The fatty acyl chains are nonpolar and hydrophobic whereas the phosphoryl alcohol head group is polar and can be solvated by H20. Phospholipids form bimolecular membranes in which the hydrophobic fatty acyl chains are located in the interior of the membrane (away from H20) and the head groups are on the surface (on either side of the membrane) and exposed to H20. Representing phospholipids as =0 (where = represents the fatty acyl chain and O the head group), we can represent such a phospholipid bilayer thus ... 

Montal M and Mueller P 1972 Formation of bimolecular membranes from lipoid... 

It turned out to be true that proteinoids, without any lipids, also form bimolecular membranes.Despite the fact that black proteinoid membranes are not as long-lived in the ultrathin state as phospholipid membranes, they last long enough to be examined. Those rich in hydrocarbon-rich amino acid side chains mostly display properties characteristic for BLMs. The same polymers are among those that most readily combine with lecithin. 

CRYSTAL-LIQUID CRYSTAL PHASE TRANSFORMATION OF SYNTHETIC BIMOLECULAR MEMBRANES... 

Figure 11 represents the schematic speculation with respect to formation of monolayer liposome for dication artificial amphiphile. In case of bimolecular membrane of dialkyl-monocation or monoalkyl-monocation artificial amphiphiles, the number of artificial amphiphile molecules must be different in the outer and the inner layers because of the different spherical surface area for the inner and the outer shells (one kind of physical nonsymmetry of membrane). On the other hand, liposome of dication artificial amphiphile must be formed by the monomolecular layer due to existence of dication groups at both ends of amphiphile molecule. However, in case of this assembly, a large amount of vacancy or defect is produced especially in the outer half of liposome as shown by the middle... 

The presence of mutually repulsive electrostatic forces between bimo-lecukr suface membranes is established. However, weak van der Waals forces arising between neutral atoms in the bimolecular membrane are attractive. Of interest in this respect, is the distance relationship that exists between van der Waals and electrostatic forces between two adjacent membranes. It is known that the van der Waals forces will fall oflF as the inverse square of the distance, while the electrostatic force will vary exponentially with the distance between the membranes. The electrostatic double layer (a repulsive force) is of definite thickness and is dependent on ionic strength. At low surface potentials, this thickness is represented by the Debye-Hiickel equation ... 

Phospholipids e.g. form spontaneously multilamellar concentric bilayer vesicles73 > if they are suspended e.g. by a mixer in an excess of aqueous solution. In the multilamellar vesicles lipid bilayers are separated by layers of the aqueous medium 74-78) which are involved in stabilizing the liposomes. By sonification they are dispersed to unilamellar liposomes with an outer diameter of 250-300 A and an internal one of 150-200 A. Therefore the aqueous phase within the liposome is separated by a bimolecular lipid layer with a thickness of 50 A. Liposomes are used as models for biological membranes and as drug carriers. 

Chemically, the membrane is known to consist of phospholipids and proteins, many of which have enzymic properties. The phospholipid molecules are arranged in a bimolecular layer with the polar groups directed outwards on both sides. The structures of some phospholipids found in bacteria are shown in Fig. 1.6. Earlier views held that the protein part ofthe membrane was spread as a continuous sheet on either side ofthe... 

The most developed and widely used approach to electroporation and membrane rupture views pore formation as a result of large nonlinear fluctuations, rather than loss of stability for small (linear) fluctuations. This theory of electroporation has been intensively reviewed [68-70], and we will discuss it only briefly. The approach is similar to the theory of crystal defect formation or to the phenomenology of nucleation in first-order phase transitions. The idea of applying this approach to pore formation in bimolecular free films can be traced back to the work of Deryagin and Gutop [71]. 

Bienvenue, E., Boudou, A., Desmazes, J. P., Gavach, C., Georgescauld, D., Sandeaux, J., Sandeaux, R. and Seta, P. (1984). Transport of mercury compounds across bimolecular lipid membranes effect of lipid composition, pH and chloride concentration, Chem.-Biol. Interact., 48, 91-101. 

Figure 2. Model membrane systems, (a) Monolayer at the gas-water interface, (b) Planar bimolecular lipid membrane (BLM). (c) Liposomes.

If the photochemical step is first order (i.e., either uni-molecular or bimolecular where the two reactant molecules are restricted to react only with each other as in a solid state or on a membrane), then we can apply unimolecular rate theory (17) to estimate E... 

It is not yet understood how life began on Earth nearly four billion years ago, but it is certain that at some point very early in evolutionary history life became cellular. All cell membranes today are composed of complex amphiphilic molecules called phospholipids. It was discovered in 1965 that if phospholipids are isolated from cell membranes by extraction with an organic solvent, then exposed to water, they self-assemble into microscopic cell-sized vesicles called liposomes. It is now known that the membranes of the vesicles are composed of bimolecular layers of phospholipid, and the problem is that such complex molecules could not have been available at the time of life s beginning. Phospholipids are the result of a long evolutionary process, and their synthesis requires enzymatically catalyzed reactions that were not available for the first forms of cellular life. 

Along these lines, supramolecular, bimolecular, as well as unimolecular approaches successfully mimicked the function of natural ion channels by using completely artificial and very simple molecules. Ion fluxes satisfied several criteria that these molecules form ion channels embedded in the bilayer lipid membrane. Non-peptidic artificial ion channels as well as helical bundles are now in our hands and it is likely that many more will soon emerge. The biological importance of these molecules may attract interest from many diverse branches of science—neurobiology, clinical medicine, biophysics, membrane technology, materials science, and others. 

I wonder whether there were some attempts to obtain the general expression for the ratio of the rates of two possible ways of bimolecular reaction between reactants A and B for the membrane surrounded by the solvent ... 

M. K. Jain, The Bimolecular Lipid Membrane A System, Van Nostrand Reinhold, New York, 1972. 

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