Sensitivity enhancement of a two-dimensional experiment for the measurement of heteronuclear long-range coupling constants, by a new scheme of coherence selection by gradients

In this work we present a new pulse sequence for the measurement of long-ra nge heteronuclear coupling constants in which the optimization of coherence selection by pulsed field gradients offers a net increase in sensitivity. This type of experiments is extremely valuable for conformational studies o f molecules in natural abundance and in this context the use of gradients i s essential for an efficient suppression of C-12 bound proton signals. A co mparative analysis of the different gradient schemes available is presented with a conclusive elucidation of the relative sensitivities. Our gradient scheme could be advantageous as a building block for other related experime nts. (C) 2001 Academic Press.