Sensitivity-enhanced sim-CT HMQC PFG-HBHA(CO)NH and PFG-CBCA(CO)NH triple-resonance experiments

Short transverse relaxation times of C-alpha and C-beta single-quantum cohe rences reduce the sensitivity of triple-resonance experiments involving tra nsfers of C-alpha/C-beta or H-alpha/H-beta coherences. Multiple-quantum lin e-narrowing techniques improve the relaxation properties of C-13 coherences , thereby increasing the sensitivity of the experiment. In the present work , we describe PFG-CBCA(CO)NH and PFG-HBHA(CO)NH experiments that utilize he teronuclear multiple-quantum coherences in a simultaneous constant-time per iod to obtain completely decoupled spectra with improved sensitivity. Resul ts indicate that similar to 30% of cross peaks show an average enhancement of similar to 15% in the CBCA(CO)NH experiment. In the related HBHA(CO)NH e xperiment, similar to 97% of the cross peaks show an average enhancement of similar to 40%. (C) 1999 Academic Press.