Protein amino acid content

Cottonseed, peanut, sesame seed, and soybean flours, when used as supplements, add to the quality of the protein. The improvement of protein quality was due to the flours compensating for limiting amino acids. Supplementation using various flours improved total protein, amino acid content and some physical characteristics in akamu, yeast bread and sugar cookies. 

Direct Determination of the Contents of Amino Acids in Proteins. Amino acid contents of proteins are presently determined, with few exceptions, on an acid hydrolysate of the protein. In some instances, however, a particular amino acid may be at least partially destroyed by the conditions for acid hydrolyses. In other instances, a particular derivative of an amino acid of the protein may be hydrolyzed by the acid condition to regenerate the original amino acid. An analysis of such a chemically modified protein would thus need to be done on the protein before acid hydrolysis. In still other instances, there may be a need to perform a large number of analyses of different proteins for a single amino acid. The availability of a simple, direct chemical method for determination of such a single amino acid would be desirable. 

The sulfur amino acid content of soy protein can be enhanced by preparing plasteins from soy protein hydrolysate and sources of methionine or cystine, such as ovalbumin hydrolysate (plastein AB), wool keratin hydrolysate (plastein AC), or L-methionine ethyl ester [3082-77-7] (alkaU saponified plastein) (153). Typical PER values for a 1 2 mixture of plastein AC and soybean, and a 1 3 mixture of alkah-saponified plastein and soybean protein, were 2.86 and 3.38, respectively, as compared with 1.28 for the soy protein hydrolysate and 2.40 for casein. 

Table 4.6 Essential amino acids content of a variety of protein sources...

Table 14.4. Essential amino acid content of the cell protein in proteins (weight %)14 comparison with other reference ...

This branch of bioinformatics is concerned with computational approaches to predict and analyse the spatial structure of proteins and nucleic acids. Whereas in many cases the primary sequence uniquely specifies the 3D structure, the specific rules are not well understood, and the protein folding problem remains largely unsolved. Some aspects of protein structure can already be predicted from amino acid content. Secondary structure can be deduced from the primary sequence with statistics or neural networks. When using a multiple sequence alignment, secondary structure can be predicted with an accuracy above 70%. 

Figure 9.2. Amino acid content (mol %) in collagen extract (dark columns) and serum proteins (light columns) from a skeleton from coastal Peru. Due to a prevalence of degraded and soluble collagen, the nonmineral-bound protein fraction shows a collagen amino acid profile.

The other example presented of a non-scrambled distribution of isotopes involves the synthesis of collagen. For a mature animal at steady state, we might expect extensive atomic scrambling in the sense that most of the non-essential amino acid content of this protein (78% of its carbon atoms) can be synthesized from the general pool of glycogenic substrates that arise from metabolism of all sugars and fats, although the pathway from fats is restricted... 

Essentially the same amino acids, and nearly equal quantities of D and L enantiomers, were detected in the Murray meteorite, another type II carbonaceous chondrite [6]. Recent expeditions to Antarctica have returned with a large number of meteorites, many of which are carbonaceous chondrites. These may have been protected from terrestrial contamination by the pristine Antarctic ice. Careful analysis of two of these, the Yamato (74662) and the Allan Hills (77306), both type II carbonaceous chondrites, by ion exchange chromatography, gas chromatography, and GC/MS, have detected a wide variety of both protein and non-protein amino acids in approximately equal D and L abundances [9,10]. Fifteen amino acids were detected in the Yamato meteorite and twenty in the Allan Hills, the most abundant being glycine and alanine. The amino acid content of the Yamato meteorite is comparable with that of the Murchison and Murray, but the Allan Hills contains 1/5 to 1/10 that quantity. Unlike earlier meteorites from other locations, the quantities of amino acids in the exterior and interior portions of the Yamato and Allan Hills meteorites are almost identical [9,10]. Thus, these samples may have been preserved without contamination since their fall in the blue ice of Antarctica, which js 250,000 years old in the region of collection. 

Amino Acid Content. Amino acid content of field pea products is related to protein level, method of processing, and fraction (starch or protein). The protein fraction contains fewer acidic (glu, asp) amino acids than the starch fraction and more basic (lys, his, arg) amino acids than the starch fraction. Also, there are more aromatic (tyr, phe) amino acids, leu, iso, ser, val, and pro in the protein fraction than in the starch fraction (5). An amino acid profile of pea protein concentrate shows relatively high lysine content (7.77 g aa/16 g N) but low sulfur amino acids (methionine and cystine) (1.08-2.4 g aa/16 g N). Therefore, it is recommended that air classification or ultrafiltration be used because acid precipitation results in a whey fraction which contains high levels of sulfur amino acids (12,23). Also, drum drying sodium proteinates decreases lysine content due to the Maillard reaction (33). 

Protein contents of selected oilseeds and legume seeds, and food protein ingredients prepared by various procedures, are shown in Table I. Amino acid contents and protein efficiency ratios (PER s)... 

The non-meat protein product must have biological quality of protein (including amino acids added) of not less than P.E.R. 2.0 (80% of casein) or an essential amino acid content (excluding tryptophan) of no less than 28% of total protein. 

PER) was modified in several respects. The diets were calculated on a 10 percent protein level rather than on an isonitrogenous basis. This was done because the nitrogen factors of the various blend components varied appreciably from the 6.25 nitrogen factor assumed in the AOAC procedure. A composite nitrogen factor for each blend was calculated from analytical results by dividing the total amino acid content by the nitrogen content. In this manner,... 

Table IV). Huff et al (11) extended these observations to include enzymatic hydrolysates of the native proteins and amino acid mixtures equivalent to soy or casein. In this experiment amino acid contents were identical among the diets fed as the three forms of each protein but the structure was different (Table V). 

Haulm (stem) The possibility of using winged bean haulm as a potential raw material for single cell protein production in the tropics has been investigated by Zomer et al. (78). Semi-sol id fermentation of haulm, using various fungi, yielded a product containing 20% true protein, a 30% increase over the native material. The fermentation also increased the sulfur amino acid content by 1.5 to 6 fold. 

FAO, "Amino Acid Content of Foods and Biol. Data on Protein, "U.N. Food and Agriculture Organization, Rome, 1970. 

A D Aniello, L Petrucelli, C Gardner, G Fisher. Improved method for hydrolyzing proteins and peptides without inducing racemization and for determining their true D-amino acid content. Anal Biochem 213, 290, 1993. 

It should also be said again that casein, the complete protein (in terms of its amino acid content), was obtained from milk. Whether highly purified by the Merck Co. or not (as in "protene"), we have noted Hopkins i ns i stence that only hot alcohol could extract the growth substances completely. Casein, Hopkins believed, could also adsorb trace amounts of these substances. McCollum, Drummond and Osborne and Mendel would all demonstrate that lactose, also obtained from cow s milk, adsorbed variable quantities of growth promoting materials. (Anyone who has left a... 

Amino Acid Content in Proteins of the Grinization Complex... 

The nutritional value of proteins (see p. 360) is decisively dependent on their essential amino acid content. Vegetable proteins—e.g., those from cereals—are low in lysine and methionine, while animal proteins contain all the amino acids in balanced proportions. As mentioned earlier, however, there are also plants that provide high-value protein. These include the soy bean, one of the plants that is supplied with NH3 by symbiotic N2 fixers (A). 

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