Membrane structural characterization

Myelin in situ has a water content of about 40%. The dry mass of both CNS and PNS myelin is characterized by a high proportion of lipid (70-85%) and, consequently, a low proportion of protein (15-30%). By comparison, most biological membranes have a higher ratio of proteins to lipids. The currently accepted view of membrane structure is that of a lipid bilayer with integral membrane proteins embedded in the bilayer and other extrinsic proteins attached to one surface or the other by weaker linkages. Proteins and lipids are asymmetrically distributed in this bilayer, with only partial asymmetry of the lipids. The proposed molecular architecture of the layered membranes of compact myelin fits such a concept (Fig. 4-11). Models of compact myelin are based on data from electron microscopy, immunostaining, X-ray diffraction, surface probes studies, structural abnormalities in mutant mice, correlations between structure and composition in various species, and predictions of protein structure from sequencing information [4]. 

Braun, V. and Rehn, K. (1969). Chemical characterization, spatial distribution and function of a lipoprotein (murein-lipoprotein) of the E. coli cell wall. The specific effect of trypsin on the membrane structure, Eur. J. Biochem., 10, 426-438. 

The biogenic amines are the preferred substrates of MAO. The enzyme comes in two flavors, MAO-A and MAO-B, both of which, like FMO, rely on the redox properties of FAD for their oxidative machinery. The two isoforms share a sequence homology of approximately 70% (81) and are found in the outer mitochondrial membrane, but they differ in substrate selectivity and tissue distribution. In mammalian tissues MAO-A is located primarily in the placenta, gut, and liver, while MAO-B is predominant in the brain, liver, and platelets. MAO-A is selective for serotonin and norepinephrine and is selectively inhibited by the mechanism-based inhibitor clorgyline (82). MAO-B is selective for /1-phcncthylaminc and tryptamine, and it is selectively inhibited by the mechanism-based inhibitors, deprenyl and pargyline (82) (Fig. 4.32). Recently, both MAO-A (83) and MAO-B (84) were structurally characterized by x-ray crystallography. 

Rubatat, L., Rollet, A. L., Dial, O. and Gebel, G. 2002. Characterization of ionomer membrane structure (Nation) by small-angle x-ray scattering. Journal of Physics IV 12(PR6) 197-205. 

Elabd, Y. A., Walker, C. W. and Beyer, F. L. 2004. Triblock copolymer ionomer membranes. Part 11. Structure characterization and its effects on transport properties and direct methanol fuel cell performance. Journal of Membrane Science 231 181-188. 

Hollosep High Rejection Type is characterized by Cellulose Tri Acetate (CTA) hollow fiber with dense membrane structure and high salt rejection, and also by the module configuration favorable for uniform flow of feed water through hollow fiber layers (5 ). These features suggest that Hollosep may be operated under the conditions of higher recovery ratio compared to conventional conditions. 

Hantke K, Nicholson G. Rabsch W, Winkelmann G (2003) Salmochelins, Siderophores of Salmonella enterica and Uropathogenic Escherichia coli Strains, are Recognized by the Outer Membrane Receptor Iron. Proc Natl Acad Sci USA 100 3677 Harada K, Tomita K, Fuji K, Masuda K, Mikami Y, Yazawa K, Komaki H (2004) Isolation and Structural Characterization of Siderophores, Madurastatins, Produced by a Pathogenic Actinomadura madurae. J Antibiot 57 125... 

Farrar, G. H. and Harrison, R. 1978. Isolation and structural characterization of alkali-labile oligosaccharides from bovine milk-fat-globule membrane. Biochem. J. 171, 549-557. 

Khoo, K.H., Nieto, A., Morris, H.R. and Dell, A. (1997c) Structural characterization of the N-glycans from Echinococcus granulosus cyst membrane and protoscoleces. Molecular and Biochemical Parasitology 86, 237-248. 

Hou, S.Y., et al. 1991. Membrane structures in normal and essential fatty acid-deficient stratum corneum Characterization by ruthenium tetroxide staining and x-ray diffraction. J Invest Dermatol 96 215. 

Eckerskom, C. and Lottspeich, F. (1993) Structural characterization of blotting membranes and the influence of membrane parameters for electroblotting and subsequent amino acid sequence analysis of proteins. Electrophoresis 14, 831-838. 

The advent of recombinant DNA technology has led to an increased interest in the structural characterization of proteins by spectroscopic methods. Few spectroscopic techniques can provide the amount of information regarding protein secondary and tertiary structure which can be obtained from circular dichroism (CD) spectroscopy. In this chapter we describe the capabilities of CD spectroscopy to provide details on the globular structure of proteins. In addition, we will provide an overview of quantitative secondary structure estimates via CD spectroscopy and of specialized CD methods for studying proteins in contact with membranes and other biomolecules. Certain aspects of protein CD spectroscopy have been previously reviewed [1-19]. 

Mizukami IF, Vinjamuri SD, Trochelman RD, Todd RF, III. A structural characterization of the Mo3 activation antigen expressed on the plasma membrane of human mononuclear phagocytes. J Immunol 1990 144(5) 1841—1848. 

The complex suite of membrane lipids would seem to create a potential for localized variation in lipid composition around specific membrane proteins. The roles played by such lipid domains are an area of active research (Williams, 1998). In view of the dynamic nature of membrane structure, however, it is extremely difficult experimentally to isolate and characterize small regions of the bilayer. Despite these difficulties, investigators of fine-scale membrane... 

Another subtlety in double bond chemistry that is important in determining the effects of double bonds on membrane structure is the position within the acyl chain at which double bonds are found. The introduction of a double bond near the center of the acyl chain, for instance at position 9 in the formation of oleic acid from stearic acid, has the largest effect on acyl chain order. Long-chain polyunsaturates with multiple double bonds have disordering influences that are highest near the membrane interior (Hazel et al., 1992). Cold acclimation is frequently characterized by the incorporation into phospholipids of long-chain polyunsaturates such as docosahexanoic (DHA) acid, a 22-carbon acid with six double bonds. 

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