Uniform 13C enrichment of proteins is commonly used for NMR studies of proteins that are not amenable to conventional homonuclear 2D NMR spectroscopy. In such studies, the one-bond 1H—13C dipolar interaction is usually the dominant source of 1H line broadening. 1H—13C zero- and double-quantum coherences are, to first order, not affected by this dipolar relaxation mechanism. The relatively long relaxation time of such 1Hα—13Cαmultiple-quantum coherences is exploited for measurement of Hα—HβJ couplings in a sample of uniformly 13C-enriched calcium-free calmodulin (16.7 kD) and a sample of TGF-β1 (25 kDa). 7(Hα—Hβ) provides information on the stereospecific resonance assignment for residues with nonequivalent Hβmethylene protons and on the χ1 torsion angles.
ASJC Scopus subject areas
- Colloid and Surface Chemistry