Membrane regulators

Blume A. Interaction of ligands with the opiate receptors of brain membranes regulation by ions and nucleotides. Proc Natl Acad Sci USA 1978 ... 

B. Biologic membranes regulate the composition and the contents within the spaces they enclose. 

Stow JL, de Almeida JB, Narula N, Holtzman EJ, Ercolani L, Ausiello DA (1991) A heterotrimeric G protein, G alpha i-3, on Golgi membranes regulates the secretion of a heparan sulfate proteoglycan in LLC-PKl epithelial cells. J Cell Biol 114 1113-1124... 

Takahashi, T., Imaia, M., Suzukia, I., and Sawai, J. (2008). Growth inhibitory effect on bacteria of chitosan membranes regulated by the deacetylation degree. Biochem. Eng.. 40, 485-491. 

The plant cell is surrounded by a cell wall, which determines many features of the plant. The outer layer of the cell wall are called middle lamella because it contains heavy layer of pectin (a polygalacturonan) that serves as the glue to hold one plant cell firmly to an adjacent cell. The inner layer of the wall is cell membrane. The cell membrane is completely different from the cell wall in form, composition, and function. Whereas the wall is a rigid, relatively thick structure, the cytoplasmic membrane is thin (approximately 75 A) and flexible. The membrane is composed of protein and lipid, whereas the wall is carbohydrate in nature. The wall provides support, whereas the membrane regulates the movement of substances into and out of the cell. 

Draeger, A., Wray, S., and E.B. Babiychuk, 2005, Domain architecture of die smooth-muscle plasma membrane regulation by annexins. Biochem J. 387(Pt 2) 309—14. 

Physically, the membrane may exist in two states the "solid" gel crystalline and the "liquid" fluid crystalline states. For each type of membrane, there is a specific temperature at which one changes into the other. This is the transition temperature (Tc). The Tc is relatively high for membranes containing saturated fatty acids and low for those with unsaturated fatty acids. Thus, bilayers of phosphatidylcholine with two palmitate residues have a Tc = 41°C but that with two oleic acid residues has a Tc = -20°C. The hybrid has a Tc = -5°C. Sphingomyelin bilayer, on the other hand, may have a Tc of close to body temperature. In the gel crystalline state, the hydrophobic tails of phospholipids are ordered, whereas in the fluid crystalline state they are disordered. At body temperature, all eukaryotic membranes appear to be in the liquid crystalline state, and this is caused, in part, by the presence of unsaturated fatty acids and in part by cholesterol. The latter maintains the fatty acid side chains in the disordered state, even below the normal Tc. There is thus no evidence that membranes regulate cellular metabolic activity by changing their physical status from the gel to the fluid state,... 

Chen, H., Born, E., Mathur, S.N., Johlin, F.C., Jr., Field, F.J. 1992. Sphingomyelin content of intestinal cell membranes regulates cholesterol absorption. Evidence for pancreatic and intestinal cell sphingomyelinase activity. Biochem. J. 286, 771-777. 

Cytoplasmic membrane regulates transport of food Into and waste production out of cell. 

Biological membranes are sheetlike structures, typically from 60 to 100 A thick, that are composed of protein and lipid molecules held together by noncovalent interachons. Membranes are highly selechve permeability barriers. They create closed compartments, which may be enhre cells or organelles within a cell. Proteins in membranes regulate the molecular and ionic compositions of these compartments. Membranes also control the flow of informahon between cells. 

The membrane is assumed to be fully hydrated. The model of membrane water management, discussed in Sect. 8.2.2, suggests that for now, in the mostly used Nafion-type membranes, with thickness in the range of 50 pm, the critical current density of membrane dehydration exceeds by far the typical current densities of fuel cell operation (experimental studies, which corroborate that the membrane regulates water fluxes in the fuel cell but its own state of hydration is not critically affected by them [125,126]. 

Theoretically, to achieve long-circulating properties and avoid extensive uptake by the liver and spleen, injected colloids should have a size between 70 nm and 200 nm (16). Atypical diameter of 100-200 nm is obtained for the pH-sensitive PEGylated liposomes presented here. The number of times the formulation is extruded through the membrane regulates size distribution, the latter becoming more uniform as the number increases. In DLS, the polydispersity index (Pdl) is calculated from the square of the normalized standard deviation (Pdl = (o/Z ) ). Acceptable Pdl values will depend on the desired properties of the vesicles, but values under 0.1 can be usually attained. 

Plereditary (trypsinogen and inhibitory protein defects, cystic fibrosis membrane regulator [CFTR] defects)... 

MEMBRANE TRANSPORT Membrane transport mechanisms are vital to living organisms. Ions and molecules constantly move across cell plasma membranes and across the membranes of organelles. This flux must be carefully regulated to meet each cell s metabolic needs. For example, a cell s plasma membrane regulates the entrance of nutrient molecules and the exit of waste products. Additionally, it regulates intracellular ion concentrations. Because lipid bilayers are generally impenetrable to ions and polar substances, specific transport components must be inserted into cellular membranes. Several examples of these structures, referred to as transport proteins or permeases, are discussed. 

The plasma membrane regulates the traffic of molecules into and out of the cell. 

Glucose transporter of animal cell plasma membrane regulated by Insulin... 

K. Kano, Y. Tanaka, T. Ogawa, M. Shimomura, Y. Okahara and T. Kunitake, Photoresponsive membranes. Regulation of membrane properties by photoreversible cis-trans isomerization of azobenzene, Chem. Lett., 1980, 421. 

Kessler, J.A., Conn, G. and Hatchers, V.B. (1986) Isolated plasma membranes regulate neurotransmitter expression and facilitate effects of a soluble brain cholinergic factor. Proc. Natl. Acad. Sci. USA 83 3528-3532. 

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