Abstract
IN developing the isotope dilution method of amino-acid analysis, we have been concerned with the difficulty of proving the purity of the isolated sample of ammo-acid, upon which the accuracy of the determination depends. Elementary analysis and the estimation of reactive groups are not always entirely satisfactory, because the contaminants most likely to be present in such purified material are those which have a very similar composition. Shemin1 has reported the contamination of glutamic acid hydrochloride by cystine dihydrochloride even after repeated crystallization, and Keston, Udenfriend and Cannan2 have emphasized the danger of co-precipitation of nearly related amino-acids and their derivatives.
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References
Shemin, D., J. Biol. Chem., 159, 439 (1945).
Keston, A. S., Udenfriend, S., and Cannan, R. K., J. Amer. Chem. Soc., 71, 249 (1949).
Kunitz, M., and Northrop, J. H., J. Gen. Physiol., 13, 781 (1930); Butler, J. A. V., ibid., 24, 189 (1940).
Dunn, M. S., Frieden, E. H., Stoddard, M. P., and Brown, H. V., J. Biol. Chem., 144, 487 (1942).
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HUGHES, I., YOUNG, G. Determination of Chemical Purity. Nature 164, 503 (1949). https://doi.org/10.1038/164503a0
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DOI: https://doi.org/10.1038/164503a0
