Multiplet component separation for measurement of methyl C-13-H-1 dipolar couplings in weakly aligned proteins

A simple spectral editing procedure is described that generates separate su bspectra for the methyl C-13-H-1(3) multiplet components of H-1-C-13 HSQC s pectra. The editing procedure relies on co-addition of in-phase and antipha se spectra and yields H-1-coupled constant-time HSQC subspectra for the met hyl region that have the simplicity of the regular decoupled CT-HSQC spectr um. Resulting spectra permit rapid and reliable measurement of H-1-C-13 J a nd dipolar couplings. The editing procedure is illustrated for a Ca2+-calmo dulin sample in isotropic and liquid crystalline phases.