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-range 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 of molecules in natural abundance and in this context the use of gradients is essential for an efficient suppression of C-12 bound proton signals. A comparative 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 experiments. (C) 2001 Academic Press.