Alloisoleucin

By measuring the L-isoleucine/o-alloisoleucine ratio in the protein isolated from the eggshells of an extinct Australian bird, a team of scientists recently determined that this bird lived approximately 50,000 years ago. Radiocarbon ( " C) dating is not accurate for samples older than about 35,000 years, so AAR is a useful addition to the tools available to paleontologists. 

The molecules of two organic compounds are sometimes composed of the same type and number of atoms, but arranged in different ways. The molecular formula of each one of such compounds, which are known as isomers (for example, isoleucine and alloisoleucine, shown in Fig. 73), is therefore identical to that of the other only the structural formulas of the two isomers show the differences between their molecules (see Textbox 63). 

N-Acetyl-isoleucin und/oder N-Acetyl-alloisoleucin 34% m.-2-Acetamino-decansdure... 

In an early paper describing this method [Science, 1970, Promote 170, 730-732], there is a note that at equilibrium a small critical excess of D-alloisoleucine is present (at 140°C they thinking report the ratio of alloisoleucine to isoleucine is 1.25), but skills that for most amino acids the equilibrium constant between the L and D forms is 1. Why should that be ... 

AASA a-aminoadipic semialdehyde, AdoHcy S-adenosylhomocysteine, AdoMet S-adenosylmethionine, Ala alanine, Arg arginine, alle alloisoleucine, Apo aminopiperidone, ASA argininosuccinate,... 

Methionine Homocitrulline Alloisoleucine Penicillamine-cysteine disulfide... 

Gibson KM, Lee CF, Bennett MJ, Holmes B, Nyhan WL (1993) Combined malonic, methylmalonic and ethylmalonic acid semialdehyde dehydrogenase deficiencies an inborn error of beta-alanine, L-valine and L-alloisoleucine metabolism J Inherit Metab Dis 16 563-567... 

A novel technique for dating archaeological samples called amino acid racemiza-tion (AAR) is based on the stereochemistry of amino acids. Over time, the configuration at the a-carbon atom of a protein s amino acids is lost in a reaction that follows first-order kinetics. When the a carbon is the only chirality center, this process corresponds to racemization. For an amino acid with two chirality centers, changing the configuration of the a carbon from L to D gives a diastereomer. In the case of isoleucine, for example, the diastereomer is an amino acid not normally present in proteins, called alloisoleucine. 

Methionine plus methionine sulfoxide. " Isoleucine plus alloisoleucine. 

Zur Benennung der Epimere der physiologisch vorkommenden Aminosauren mit zwei Chiralitatszentren gibt es eine besondere Vor-silbe, namlich die Vorsilbe Alio-. Demnach heifien die Epimere von Threonin und Isoleucin Allothreonin bzw. Alloisoleucin. 

Nutritional and Physiological Effects of Alkali-Treated Proteins. The first effect of the alkaline treatment of food proteins is a reduction in the nutritive value of the protein due to the decrease in (a) the availability of the essential amino acids chemically modified (cystine, lysine, isoleucine) and in (b) the digestibility of the protein because of the presence of cross-links (lysinoalanine, lanthionine, and ornithinoalanine) and of unnatural amino acids (ornithine, alloisoleucine, / -aminoalanine, and D-amino acids). The racemization reaction occurring during alkaline treatments has an effect on the nitrogen digestibility and the use of the amino acids involved. 

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