Hydrophobic barrier

The slope of the water solubiUty curves for fuels is about the same, and is constant over the 20—40°C temperature range. Each decrease of 1°C decreases water solubiUty about 3 ppm. The sensitivity of dissolved water to fuel temperature change is important. For example, the temperature of fuel generally drops as it is pumped iato an airport underground hydrant system because subsurface temperatures are about 10 °C lower than typical storage temperatures. This difference produces free water droplets, but these are removed by pumping fuel through a filter-coalescer and hydrophobic barrier before deUvery iato aircraft. 

Wisniewska, A. and W.K. Subczynski. 1998. Effects of polar carotenoids on the shape of the hydrophobic barrier of phospholipid bilayers. Biochim. Biophys. Acta 1368 235-246. 

Membranes of extreme halophilic (Kushwaha et al. 1975, Anwar et al. 1977, Anton et al. 2002, Lutnaes et al. 2002, Oren 2002) and thermophilic bacteria (Alfredsson et al. 1988, Yokoyama et al. 1995) contain a large concentration of polar carotenoids. Membranes of these bacteria, which live in extreme conditions, should provide a high barrier to block nonspecific permeation of polar and nonpolar molecules. Incorporation of dipolar carotenoids into these membranes at a high concentration serves this purpose well because dipolar carotenoids increase the hydrophobic barrier for polar molecules (Wisniewska and Subczynski 1998, Wisniewska et al. 2006) and increase the rigidity barrier... 

Griffith, O. H., P. J. Dehlinger, and S. P. Van. 1974. Shape of the hydrophobic barrier of phospholipids bilayers (Evidence for water penetration into biological membranes). J. Membr. Biol. 15 159-192. 

Subczynski, W. K., A. Wisniewska, J.-J. Yin, J. S. Hyde, and A. Kusumi. 1994. Hydrophobic barriers of lipid bilayer membranes formed by reduction of water penetration by alkyl chain unsaturation and cholesterol. Biochemistry 33 7670-7681. 

Exploration of the use of liposomes in wool processing stems from the similarity that exists between the bilayer structure of the cell membrane complex of wool and that of the liposomes. Merino wool contains about 1% by weight of lipids, these forming the hydrophobic barrier of the cell membrane complex. Cholesterol is one of the main lipid... 

Lipoprotein lipases, which act on the lipoproteic bonds of lipoproteins (combinations of proteins with fatty ester molecules), thus breaching the hydrophobic barriers formed by these compounds. 

Circle sections with a hydrophobic barrier pen (e.g., Dako Pen, S2002) and proceed with immunohistochemical staining protocol. Do not allow sections to dry for the remaining procedure. 

The relevance of such a diastereomer discrimination to the transport of chiral molecules, such as pharmaceuticals or biochemicals, through hydrophobic barriers, such as cell membranes, is obvious. Furthermore, since poly(DL-lysine) followed the same general pattern of behavior displayed by the other three samples, the observed surface-pressure changes probably were not due to helicalization of the polypeptide. Whereas poly(L-lysine) and poly(D-lysine) form helices with opposite screw sense, the random copolymer poly(DL-lysine) is to a large extent prevented from forming helices. 

Octanol is the most widely used model of a biological membrane [18] and logDy 4 values above 0 normally correlate with effective transfer across the lipid core of the membrane, whilst values below 0 suggest an inability to traverse the hydrophobic barrier. 

Tissue sections should not be dried during immunological BISH detection. A humidity chamber/box can be assembled by placing wet paper towels in a tray and covering it with a plastic wrap sheet. PAP pen is often used for creating a hydrophobic barrier that is dissolved with xylene for immunohistochemistry. However, because BISH detection... 

A model of the gate in the closed acetylcholine channel. The M2 helices are bent about halfway across the phospholipid bilayer. A leucine side chain (L) from each of the five helices projects into the channel here, forming a hydrophobic barrier to the diffusion of ions. (From N. Unwin, Nicotinic acetylcholine receptor at 9 A resolution, J. Mol. Biol. 229 1101, 1993. Reprinted by permission.)... 

Biological membranes present a barrier to the free transport of cations, as the hydrophilic, hydrated cations cannot cross the central hydrophobic region of the membrane which is formed by the hydrocarbon tails of the lipids in the bilayer. Specific mechanisms thus have to be provided for the transport of cations, which therefore allow for the introduction of controls. Such translocation processes may involve the active transport of cations against the concentration gradient with expenditure of energy via the hydrolysis of ATP. These ion pumps involve enzyme activity. Alternatively, facilitated diffusion may occur in which the cation is assisted to cross the hydrophobic barrier. Such diffusion will follow the concentration gradient until concentrations either side of... 

Lichtenberger, L. M. The hydrophobic barrier properties of gastrointestinal mucus. Annu. Rev. Physiol. 57 565-583, 1995. 

For the transmembrane transfer of ions containing hydrophobic substituents the model was proposed that takes into account the variations of dielectric properties across the membrane. According to this model [194-200] the lipophilic ions are adsorbed at the minima of the potential energy near to the membrane // water interface (see Fig. 6b). The transfer of the ions across the membrane is considered to be monomolecular reaction of the ion s surmounting of the hydrophobic barrier in the center of the membrane with the first order rate constant k,. 

From the schematic model of the plasma membrane we have just depicted, it is clear that the two sides, the inner and the outer surfaces, should have different functions as a result of different structures. Moreover, the lipid bilayer may be considered as a hydrophobic barrier preventing diffusion of water-soluble molecules from both sides, thus maintaining a permanent distinction between the inside and outside of a cell. It also allows the membrane to form closed vessels, which appear to be an absolute requirement for maintaining the fixed asymmetric orientations of the cell membrane constituents. 

Electrochemistry of respiration — The function of the enzymes in the mitochondrial respiratory chain is to transform the energy from the redox reactions into an electrochemical proton gradient across the hydrophobic barrier of a coupling membrane. Cytochrome oxidase (EC 1.9.3.1, PDB 20CC) is the terminal electron acceptor of the mitochondrial respiratory chain. Its main function is to catalyze the reaction of oxygen reduction to water using electrons from ferrocytochrome c 4H+ + 02 + 4e 2H20. This reaction is exother-... 

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