NMR characterization of I,I-selenocystine with 92% 77Se enrichment

Techniques for the biosynthetic incorporation of selenomethionine into biomolecules have recently been exploited to produce both heavy-atom derivatives and NMR probes for the elucidation of local and global structures of a variety of biological macromolecules. Since the work of Bock and co-workers in 1994, also chalcogen analogue replacement of cystine by selenocystine residues in proteins can be achieved to study structural, mechanistic and functional aspects of enzymes. This paper reports the H-1 and Se-77 NMR spectroscopic characterisation of 1,1-selenocystine with 77Se at natural abundance and 92% enriched: delta(H-1), delta(Se-77); (1)J(Se-77,Se-77'), (2)J((HBbeta 1,beta 2)-H-1,Se-77), (3)J((HBbeta 1,beta 2)-H-1, 77Se'), (3)J(H-1(alpha), Se-77); T-1(Se-77), T-2(Se-77), T-1p(Se-77). The linewidth of the 77Se resonance of selenocystine is dominated by chemical shift anisotropy relaxation, as shown by its dependence on the square of the magnetic field. The reported parameters will serve as reference data for the biomolecular NMR spectroscopy of Se-77-labeled proteins where the cysteine has been replaced by selenocysteines. Copyright (C) 1999 John Wiley & Sons, Ltd.