Cell membranes, biochemical properties

The sodium and calcium pumps can be isolated to near purity and still exhibit most of the biochemical properties of the native pump. Some kinetic properties of these pumps in native membranes are altered or disappear as membrane preparations are purified. For example, when measured in intact membranes, the time-dependencies of phosphorylation and dephosphorylation of the pump catalytic sites exhibit biphasic fast to slow rate transition this characteristic progressively disappears as the membranes are treated with mild detergents. One suggested explanation is that, as the pumps begin to cycle, the catalytic subunits associate into higher oligomers that may permit more efficient transfer of the energy from ATP into the ion transport process [29, 30], Some structural evidence indicates that Na,K pumps exist in cell membranes as multimers of (a 3)2 [31]. 

The mercuric ion, Hg2 +, which is obtained after oxidation in the red blood cells and other tissues, is able to form many stable complexes with biologically important molecules or moieties such as sulphydryl groups. The affinity of mercury for sulphydryl groups is a major factor in the understanding of the biochemical properties of mercuric compounds, resulting in interference with membrane structure and function and with enzyme activity. 

Mitochondria are intracellular centers for aerobic metabolism. They are cell organelles that are identified by well-defined structural and biochemical properties. In morphological terms, mitochondria are relatively large particles that are characterized by the presence of two membranes, a smooth outer membrane that is permeable to most important metabolites and an inner membrane that has unique transport properties. The inner membrane is highly folded, which serves to increase its surface area. Figure E10.1, which shows the structure of a typical mitochondrion, divides the organelle into four major components inner membrane, outer membrane, intermembrane space, and the matrix. These regions are associated with different and... 

The key experiment was one which would not be carried out until Skou learned of a paper published in German four years earlier, which showed that the movement of cations across the red cell membrane was inhibited by cardiac glycosides such as ouabain, plant alkaloids used for some 200 years in the therapy of heart failure. In 1957, Skou was unaware of this important finding, and wrote later that he had not done the crucial experiment to show Na/K ATPase as the transport system. When done, the experiment was decisive ouabain inhibited the ATPase activity exactly as it did the cation fluxes. This led to a flurry of activity in many biochemical laboratories and allowed Skou (nine years after his original publication) to write a review in which he concluded that the enzyme fulfilled the requirements for a system responsible for active transport of Na+ and K+ across the cell membrane. Thus the Na/K ATPase had the following properties ... 

Samson, G., and Visser, S. S. (1989). Surface-active effects of humic acids on potato cell membrane properties. Soil Biol. Biochem. 21,343-347. 

The results of several investigations on the mechanism of action of tumoricidal ether phospholipids support the assumption that biochemical and physicochemical properties of the cell membrane are involved. 

In recent years nonlinear optical materials on the basis of nitroazoles, especially nitrobenzoxazoles and nitrobenzoxadiazoles, have investigated under intense scrutiny, at that and UV and fluorescence spectroscopy is widely used in studying of their structure and dynamics [1202-1225], 4-Aminosubstituted 7-nitrobenzofura-zans have a strong band in the visible region ( =457-483 nm) due to their chromophore properties [777]. 4-Substituted 7-nitrobenzofurazans possess a strong fluorescence that has led to their use as biochemical fluorescent probes in cell membranes [777, 1226-1228],... 

Hu, W., Jones, P. D., De Coen, W., Newsted, J. L., Giesy, J. P. Alterations in cell membrane properties caused by perfluorinated compounds. Comp. Biochem. Physiol C Pharmacol, 135C 77-88 (2003). 

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