The new active-coupling-pattern tilting experiment for an efficient and accurate determination of homonuclear coupling constants

A new constant-time COSY experiment which allows an efficient determination of accurate homonuclear coupling constant values is presented. Characteristic features include an improved scheme for homonuclear active-coupling-pattern tilting (ACT) and an arbitrarily scaled shift and coupling information (ASSCI) design of the F1 domain. As a result, simple and easy to interpret tilted cross-peak patterns, even for two-spin systems, are obtained with good sensitivity. The relative spacing of chemical-shift differences and coupling splittings is largely under experimental control. The effectiveness of the spectral region selective variant of the new sequence is demonstrated by a determination of the 3JHN, Halpha couplings in a peptide sample. The multiplet-selective variant is shown to produce good results with a terpene. The superiority of the new ACT scheme is additionally demonstrated by an ACT-J spectrum of the peptide. Copyright 1998 Academic Press.