Fractional composition, lysine

Case study 4.4 The fractional composition of a solution of lysine 166... 

Fig. 4.16 The fractional composition of the protonated and deprotonated forms of lysine (Lys) in aqueous solution as a function of pH. Note that conjugate pairs are present at equal concentrations when the pH is equal to the pfQ of the acid member of the pair.

Figure 4 Adsorption of lysine-13 polypeptide onto ternary phosphatidylcholine (PC)/ phosphatidylserine (PS)/PIP2 lipid membrane with 74 25 1 composition (panels A and B), and onto binary PC/PS lipid membrane with 71 29 composition (panel C). (a) Normalized local fraction of PIP2 lipids in the ternary system, (b) Local PS lipid fractions in the ternary system, (c) Local PS lipid fraction in the binary mixture. All plots shown for f=0.5 ts after beginning of propagation. For these calculations lysine-13 was placed near the membrane, such that the minimum distance between van der Waals radii of lysine-13 and membrane atoms was 3 A, and the peptide was oriented with its major (long) axis parallel to the bilayer plane.

Nonionic block copolypeptides made of PEGylated L-lysine and L-leucine residues, PELLys- -PLLeu (Fig. lOh) have also been described [52], The copolymers adopted a rod-like conformation, due to the strong tendency of both segments to form a-helices (CD spectroscopy), and produced a variety of self-assembled structures in aqueous solution. Micrometer vesicles and sheet-like membranes could be obtained for copolymers with fractions of the hydrophobic leucine ranging from 10 to 30mol%. Conventional uncharged block copolymers of this composition would be expected to form spherical or cylindrical micelles. The assembly into bilayers was related to a secondary structure effect, as illustrated in Fig. 12. Accordingly, samples with the same composition but nonhelical chain conformation (CD),... 

This was possible to detect because the monoculture of Thalassiosira rotula employed showed partly synchronized cell divisions during exponential growth. Brockmann et al. [137] carried out combined measurements of dissolved amino acids and carbohydrates. Glucose and lysine occurred in highest concentrations. Mague et al., [22] found that extracellular production of free amino acids counted for 7.1% of the of the total extracellular C released in an exponentially growing culture of S. costatum Myklestad et al., [26] measured 10.7% for C. affinis or 3.6% when calculated as percent of total incorporated cell N. In contrast to this Admiraal et al., [139] found that none of three benthic diatoms released more than 0.1 % of the cellular N as free amino acids and concluded that benthic diatoms may act as net consumers of amino acids. Several authors did measure both intracellular and extracellular concentrations of many amino acids [22 140 -142]. The clear difference in relative composition of intracellular and extracellular fractions as pointed out by the first mentioned of these authors, show that the released pool is not just a portion of the intact cells content. 

The amino add compositions of SCMKB fractions from a variety of mammalian fibers generally show similarities in being rich in half-cystine, proline, serine, and threonine. These four residues generally account for at least half the total residues. Residues such as lysine, histidine, tyrosine, and phenylalanine are generally low in SCMKB fractions, and methionine is usually absent [226,227]... 

Many laboratories have succeeded in fractionating histones by selective extraction and differential precipitation. The selective extraction procedure is based on the difference in the amino acid composition of the various types of histones. For example, a histone-rich lysine can be obtained by extraction from whole thymus with 5% perchloric acid followed by precipitation with 10% trichloroacetic acid. If the histones found in the perchloric acid extract are passed through a carboxymethyl-cellulose column and eluted from the column with borate buffer at pH 9, then different components called 1, 2, and 3 can be recovered. 

Edible protein. The protein fraction of tomato seed is about 35% of the dry weight. This is higher than that of cottonseed which is about 20% protein (Morad et al., 1980). Three cultivars of tomato examined for amino acid composition had higher levels of lysine compared to commercial soybean meal (Rymal et al., 1974). Soymeal was higher in threonine, serine and histidine than tomato meal while both meals were low in methionine. Blended with low lysine protein sources, the tomato meal may be useful for balancing essential amino acids. The protein comprised about 33% of the seed (Bertoni et al., 1963). The limiting amino acids in tomato seed are methionine and cystine. 

In contrast, the peptide fraction from calf prochymosin has a composition (Table VI) resembling that of residues 1-27 in the prochymosin sequence (Fig.l). After removal of the excess of pepstatin on Bio-Gel P2, the prochymosin peptide had the composition shown in the last column of Table VI. For the sake of brevity the details of the protein fraction from prochymosin are not given but this showed a composition intermediate to prochymosin and chymosin, particularly in the values for lysine and leucine which reflect the largest changes. 

A hyaluronate lyase from group A Streptococci has been purified (1000-fold) by ion-exchange chromatography and gel filtration two fractions with identical amino-acid compositions were obtained. The enzyme was inhibited by A-(toIuene-/7-sulphonyl)phenylalanine chloromethyl ketone and iV-(toluene-p-sulphonyl)lysine, and did not depolymerize hyaluronic acid methyl ester. Photo-oxidation in the presence of Methylene Blue inactivated the enzyme, whose action probably involves the transfer of a proton between a histidyl residue of the enzyme and a carboxy-group of the substrate. 

For assembly of novel three-dimensional (3D) structures, block copolypeptides are required that have structural domains (i.e., amino acid sequences) whose size and composition can be precisely adjusted. Such materials have proven elusive using conventional techniques. Strong base-initiated NCA polymerizations are very fast. These polymerizations are poorly understood and well-defined block copolymers cannot be prepared. Primary amine-initiated NCA polymerizations are also not free of side reactions. Even after fractionation of the crude preparations, the resulting polypeptides are relatively ill-defined, which may complicate unequivocal evaluation of their properties and potential applications. Nevertheless, there are many reports on the preparation of block copolypeptides using conventional primary amine initiators. Examples include many hydrophilic-hydrophobic and hydrophilic-hydrophobic-hydrophilic di- and triblock copolypeptides (where hydrophilic residues were glutamate and lysine, and hydrophobic residues were leucine, valine, isoleucine, phenylalanine, and alanine" ) prepared to study... 

Fractions 14 through 19 aire complex peptides containing more than one basic residue. They presumably represent products resulting from incomplete digestion of the mercuripapain. The purity of these peptides has not been established, so that it has been impossible to deduce unequivocal sequences from the amino acid composition. Furthermore, the presence of these complex fragments has a marked influence on the yield of fractions containing one residue of arginine or lysine. The yield of these fractions has varied from 25 to 100%. 

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