Abstract
IF the enantiomorph (unlabelled) of a labelled isomer is available, the maximum contamination of the particular labelled compound by its enantiomorph may be assessed by a crystallization method. Repeated crystallization of a mixture of enantiomorphs in which one (unlabelled) is present in large excess of the other (labelled) would be expected to lead to a purification of the more abundant isomer; hence, the presence of isotope in the purified abundant isomer should represent contamination of the labelled antipode. Thus, when enzymatically prepared1,2 D-glutamic acid-2-14C was diluted about 2,000-fold with carrier L-glutamic acid and the mixture crystallized, via the hydrochloride and the free amino-acid, to constant specific activity, it could be calculated that the maximum amount of contaminant L-glutamic acid-2-14C was less than 1 per cent3.
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References
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MINTHORN, M., KOEPPE, R. Crystallization of Non-Racemic Mixtures of the Isomers of Serine. Nature 185, 459–460 (1960). https://doi.org/10.1038/185459a0
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DOI: https://doi.org/10.1038/185459a0
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