Spectra plasma membrane

Early endosomes are the main sorting station in the endocytic pathway. In their acidic interior (pH 5.9-6.0), the receptor and its ligand can be released. The receptor may be recycled to the surface by vesicles that fuse with the plasma membrane. Material that cannot escape from the early endosomes is further transported via multivesicular bodies to late endosomes and digesting lysosomes that contain a broad spectrum of peptidases and hydrolases in an acidic surrounding [for reviews on endocytosis see Refs. (10-12), for review on clathrin uptake see Refs. (9,13)]. 

Calcium is the principal extracellular electrolyte regulated by PTH, calcitonin, and D3. Extracellular calcium is a critical component of signal transduction across the plasma membrane, which regulates a wide spectrum of physiological events including muscle contraction, secretion of neurotransmitters and hormones, and the ac-... 

Activation of phospholipase Cp (Figure 8.2c). This enzyme is associated with the iimer surface of the plasma membrane and splits the phospholipid phosphatidylinositol4,5-bisphosphate into diacylglyc-erol (DAG) and inositol-1,4,5-triphosphate (IP3). Dia-cylglycerol is hydrophobic and remains associated with the membrane, where it will activate protein kinase C, which in turn will activate a broad and cell-dependent spectrum of target proteins. IP3 is water-soluble and... 

Insulin action is initiated by binding of the hormone to its specific receptor at the plasma membrane. This induces a broad spectrum of distinct effects at a number of different target cells, predominantly in muscle, liver and fat. These cellular insulin effects can be divided into four categories ... 

Figure 11. NMR spectra (46.1 MHz) of the plasma membranes of Achole-plasma laidlawii enriched in myristic acid labeled at the terminal methyl group (C-14 0-w s 90%), at the indicated temperatures. The numbers to the right of each spectrum are the fractions of liquid-crystalline lipid calculated by the moment analysis of Ref. 27. (Unpublished data of H. C. Jarrell, R. Deslauriers, and...

An approach somewhat analogous to that of Barnes and Hu was adopted by Pickard and Rosenbaum.They examined the effects of an impressed radiofrequency field on the resting potential across the plasma membrane and the effects of such fields with regard to ion transit time within an ion channel spanning the membrane. Of interest is their conclusion that the frequency range at which transit time effects are no longer important lies well below the microwave portion of the spectrum. This estimate was based upon data for the sodium ion current in the squid axon membrane. 

Figure 9.12 Direct electrospray ionization-mass spectrometry analysis of human erythrocyte plasma membrane phospholipids (A) A positive-ion electrospray ionization (ESI) mass spectrum of erythrocyte plasma membrane phospholipid extract showing 14 molecular species of glycerophospholipids and 4 molecular species of sphingomyelin (B) A negative-ion ESI mass spectrum of the same extract of plasma membrane phospholipids showing more than 25 molecular species of ethanolamine glycerophospholipids and 8 molecular species of serine and inositol glycerophospholipids. Reprinted with permission from Han, X. and Gross, R. W., Electrospray ionization mass spectroscopic analysis of human erythrocyte plasma membrane phospholipids, Proc. Natl Acad. Scl USA, 91(22), 10635-9. Copyright (1994) National Academy of Sciences, USA.

Rieske protain/centar an iron-sulphur protein first isolat from Complex III of the mitochondrial electron transport chain, in which it occurs with cytochromes b and C) [J.S, Rieske el al. Biochem. Biophys Res Commun. IS (1%4) 338-344], but which has now been found in the equivalent cytochrome be complexes in the bacterial plasma membrane and the chloroplast thylakoid membrane. The latter, known as the cytochrome bff complex, partidpates in cyclic and noncyclic electron flow in the light phase of photosynthesis (see Photosynthesis). All Rieske proteins are one-electron redox systems with a standanl redox potential in the + 0.2 to + 0.3V range and have a (2Fe-2S] center, a single membrane-spanning a-helix, and a characteristic electron spin resonance (ESR) spectrum. The chloroplastidic R.p/c, with a M, of - 20,000, is smaller than that of the mitochondnon. It is encoded in the nucleus, synthesized in the cytoplasm and translocated to the chloroplast, where it is inserted into the thylakoid membrane. Within the thylakoid membrane its [2Fe-2S] redox centre (near to its C-terminus) can readily pass electrons to cytochrome /, a c-type cytochrome that projects from the luminal surface cytochrome / then passes electrons to plastocyanin (see) dissolved in the aqueous milieu of the thylakoid lumen. 

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