Abstract:
It is intended to provide a stable isotope-labeled amino acid which is at least one of amino acids constituting protein, characterized by having at least one of the following labeling patterns: (a) in one or more methylene groups, methylene hydrogen atoms other than at least one have been deuterated; (b) in prochiral gem-methyl groups, hydrogen atoms in one of the methyl groups have been completely deuterated; (c) in prochiral gem-methyl groups, hydrogen atoms in the methyl groups have been partially deuterated; and (d) hydrogen atoms in a methyl group other than one have been deuterated while hydrogen atoms in an aromatic ring have been partially deuterated. Using this stable isotope-labeled amino acid, deuterium substitution of a protein can be achieved without worsening the NMR sensitivity of the residual hydrogen nucleus. Thus, an NMR spectrum of a high-molecular weight protein exceeding the upper limit applicable in the prior art can be quickly and surely analyzed and the stereostructure can be highly precisely determined at the same time.