S. Grzesiek et al., MULTIPLE-QUANTUM LINE NARROWING FOR MEASUREMENT OF H-ALPHA-H-BETA J-COUPLINGS IN ISOTOPICALLY ENRICHED PROTEINS, Journal of the American Chemical Society, 117(19), 1995, pp. 5312-5315
Uniform C-13 enrichment of proteins is commonly used for NMR studies o
f proteins that are not amenable to conventional homonuclear 2D NMR sp
ectroscopy. In such studies, the one-bond H-1-C-13 dipolar interaction
is usually the dominant source of H-1 line broadening. H-1-C-13 zero-
and double-quantum coherences are, to first order, not affected by th
is dipolar relaxation mechanism. The relatively long relaxation time o
f such H-1(alpha)-C-13(alpha) multiple-quantum coherences is exploited
for measurement of H-alpha-H-beta J couplings in a sample of uniforml
y C-13-enriched calcium-free calmodulin (16.7 kD) and a sample of TGF-
beta 1 (25 kDa). J(H-alpha-H-beta) provides information on the stereos
pecific resonance assignment for residues with nonequivalent H-beta me
thylene protons and on the chi(1) torsion angles.