Amino acid fractions

Ion-exchange chromatography makes use of the fact that proteins differ enormously in their affinity for positively or negatively charged columns. However, the cross-linked resins used in amino acid fractionation (see chap-... 

Rohan had suggested that the operative reaction in the development of chocolate aroma might be a Strecker degradation of the amino acid fraction. Bailey et al. (8) demonstrated quantitatively that three aldehydes, which could be related to leucine, valine, and alanine, were prominent in the volatiles from a typical sample of roasted, ground cacao beans. 

The reverse route, however, i.e., formation of the cyclol group followed by the introduction of the a-amino acid fraction, produced the desired compound (92). It was observed that cyclol formation occurred spontaneously if certain structural conditions were fulfilled and that the system underwent considerable stabilization upon cyclolization. 

D/L enantiomeric ratios for alanine, valine, glutamic acid, leucine, proline, and phenylalanine in the remaining half of the desalted amino acid fraction were obtained by gas chromatography (15). Hie N-trifluoroacetyl-L-prolyl-DL-amino acid esters were synthesized, then separated on a Hewlett-Packard Model 5711A Gas Chromatograph with flame ionization detector and a 12 foot colunn of Chromasorb W-AW-DMCS solid support coated with 8% SP 2250. 

Table II. Radiocarbon Determinations on the Carbonate, Collagen, and Amino Acid Fractions of Two Human Bone Samples...

Fraction studies have been applied to the study of the reliability of bone values by measuring the comparative ages of the carbonate, collagen, and amino acid fractions in single bone samples. Table II lists results obtained on two duplicate sample suites from a single burial. These data continue to support the early view that the carbonate fraction... 

The attempts to use some of the more established reagents for specific analysis of protein e.g. Folin-phenol reagent or the variation of the method by Lowry et al. (1951), whereby total protein content is calculated from the content of aromatic amino acids (tryptophan, tyrosine and phenylalanine), lacks the sensitivity for determinations on seawater samples (Wangersky and Zika, 1978). Furthermore, detailed analysis of the combined amino acid fraction of seawater does not show any aromatic amino acid to be present in significant quantity (Garrasi et al., 1979). 

Visser, F. M. W. (1977c). Contribution of enzymes from rennet, starter baaeria and milk to proteolysis and flavour development in Gouda cheese. 3. Protein breakdown analysis of the soluble nitrogen and amino acid fractions, Neth. Milk Dairy J. 31,210-239. 

The structure of voaluteine (rupicoline, voacangine pseudoindoxyl) was deduced from physical measurements. Of diagnostic value was the shielded methyl of the methoxyl 3.30 ppm (see voacangine 3.73 ppm). Attempts to prove the structure by chemical degradation were not successful (14). Preliminary attempts to hydrolyze voaluteine with acid or base were not encouraging. Hydrolysis was slow and was accompanied by general decomposition. The crude amino acid fractions upon re-methylation with diazomethane yielded only traces of voaluteine (14). 

Studies of individual or several amino acids Analysis of types of amino acids Fractionation and peptide analysis... 

Purification of amino acids is required under circumstances in which maximum sensitivity is required or when interfering compounds are present The total amino acid fraction may be isolated by lon-exchange chromatography with Dowex 50W-X8 (Moroni et al., 1980 Moroni et al., 1981). In other derivatization procedures, asparagine is hydrolyzed to aspartate and, similiarly, glutamine to glutamate In these cases, selective isolation of glutamate and aspartate with Dowex AG 1-X8 (Corradetti et al., 1983) is preferred. 

FIGURE 2. Distribution of C into the amino acids fractions of pea leaflets, stipules and tendrils. 

Our knowledge of secondary compounds is limited mostly to those that are accumulated, but, in some instances, compounds normally not thought to be present have been found at very low levels. For example, azetidine-2-carbox-ylic acid, normally found in the Liliaceae and in some legumes, has been isolated from amino acid fractions of sugar beets Beta vulgaris, Chenopodiaceae) isolated as a by-product of sugar manufacture. A number of other unusual amino acids also were isolated from the mixture. About 500 kg of these fractions is obtained from 10 tons of sugar beets (Fowden, 1972). The formation of quinolizidine alkaloids... 

Kasai, T., M. Sano, and S. Sakamura Amino acid composition of broad bean (Vida faba). I. Pattern of acidic amino acid fractions. Nippon Nogei Kagaku Kaishi... 

Kasai, T., M. Ueda, S. Sakamura, and K. Sakata Amino acid composition of ladino clover (Trifolium repens L. var. giganteum). (Studies on the components in acid amino acid fraction Part I.) Nippon Nogei Kagaku Kaishi 47, 583 (1973). (In Japanese with English summary.)... 

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