Lipid amino acid composition

The amino acid compositions and sequences of the /3-strands in porin proteins are novel. Polar and nonpolar residues alternate along the /3-strands, with polar residues facing the central pore or cavity of the barrel and nonpolar residues facing out from the barrel where they can interact with the hydrophobic lipid milieu of the membrane. The smallest diameter of the porin channel is about 5 A. Thus, a maltodextrin polymer (composed of two or more glucose units) must pass through the porin in an extended conformation (like a spaghetti strand). 

If the virus is treated with proteolytic enzymes the fuzzy layer formed by the viral spikes is removed (Osterrieth, 1965 Compans, 1971 Gahm-berg et al, 1972 Sefton and Gaffney, 1974 Utermann and Simons, 1974). Remnants of both El and E2 are left in the bilayer. These have a hydrophobic amino acid composition, and are soluble in lipid solvents such as chloroform-methanol. The amphiphilic nature of the spike protein is also evident from its capacity to bind Triton X-100 (0.6 g/g protein) which binds to the hydrophobic part to form a water-soluble protein-detergent complex (Simons et al., 1973a). The ability of amphiphilic proteins to bind Triton can be used to separate them from hydrophilic proteins using an extraction procedure recendy described... 

In addition to carbohydrates, extrafloral nectar may contain variable amounts of proteins, amino acids, and lipids (Baker et al., 1978 Smith et al., 1990). The particular amino acid composition can increase the attractiveness of extrafloral nectar as a food source (Lanza, 1988). Nevertheless, extrafloral nectar by itself falls short from providing a well-balanced diet. Low amino acid levels or the absence of certain essential amino acids forces nectar consumers to seek out supplementary protein sources, thereby stimulating predation. 

The amino acid composition of milk lipid globule membranes, as determined by several groups, has been summarized elsewhere (Patton and Keenan 1975). Some differences are evident in the data from differ-... 

Although proteins and amino acids in the food influence the metabolism of the fish, they do not alter the amino acid composition of proteins in the body. In contrast, the lipids in the body of the fish are greatly influenced by the dietary lipids. In particular, it is the triacyl-glycerols (the main constituents of reserve energy) which are influenced by diet (Lovem, 1937,1942,1964 Kelly et al., 1958 Brockerhoff et al., 1963, 1964 Ackman, 1964, 1967 Ananyev, 1965 Ackman and Eaton, 1966, 1976). Food lipids also influence the structural lipids of the fish. 

Sergeeva, N.T. (1985). Effect of imbalance of fatty acid and amino acid composition of food on lipid metabolism in rainbow trout (In Russian). In Plastic Metabolism in Fish , pp.15-21, Kaliningrad. 

Gur yanova, S. D. (1977). [The amino-acid composition of the total proteins of plerocercoids of the genus Diphyllobothrium and their hosts.] In Russian. In [Comparative biochemistry of fish and their helminths. Lipids, enzymes, proteins. (Collected uwfcy).] ed. V. S. 

The molar ratios of most of the amino acids in the protein of the German cockroach are generally similar to those of vertebrates and other invertebrates with respect to whole animal protein hydrolyzates (1). However, histidine, lysine, tyrosine, leucine, isoleucine, valine, and alanine are somewhat more abundant in cockroach protein and there is less cystine. The data vary significantly from data previously reported on the amino acid composition of the German cockroach (7). The earlier analysis, however, was conducted on insects with the entire head and digestive tract removed and the remaining portions of the body extracted with lipide solvents only. 

Protein is an essential nutrient for human growth, development, and homeostasis. The nutritive value of dietary proteins depends on its amino acid composition and digestibility. Dietary proteins supply essential amino acids, which are not synthesized in the body. Nonessential amino acids can be synthesized from appropriate precursor substances (Chapter 17). In human adults, essential amino acids are valine, leucine, isoleucine, lysine, methionine, phenylalanine, tryptophan, and threonine. Histidine (and possibly arginine) appears to also be required for support of normal growth in children. In the absence from the diet of an essential amino acid, cellular protein synthesis does not occur. The diet must contain these amino acids in the proper proportions. Thus, quality and quantity of dietary protein consumption and adequate intake of energy (carbohydrates and lipids) are essential. Protein constitutes about 10-15% of the average total energy intake. 

Given their amino acid composition (Parsons etal., 1984), eukaryotic plankters should have proteins with C N ratios in the range 3 1 1. Compounds with porphyrin rings, such as chlorophyll or the haem cofactors of cytochromes, have C N between 8 and 14 1. Nucleic acids, the greatest part found in ribsomal RNA and nucleotides, have C N P of about 10 4 1. Lipids and carbohydrates are devoid of N and P, except for C P of at least 40 1 in phospholipid membranes (see Geider and La Roche (2002) for more details). 

The precipitated proteins can be purified by washing with hot trichloroacetic acid to remove nucleic acids and with a variety of organic solvents to remove lipids. The proteins can then be hydrolyzed, usually with 6N HCl under vacuum at 120°C for 24 h or more, and their amino acid composition determined There are losses of some amino acids during hydrolysis—Asn, Gin, and... 

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