Selective measurements of long-range homonuclear J-couplings in solid-state NMR This work is dedicated to the memory of Dr. Jean-Pierre Dulcère, who co-founded the NMR center at Aix-Marseille Université.

摘要

We demonstrate here that the principle of frequency-selective spin-echoes can be extended to the measurements of long-range homonuclear scalar J-couplings in the solid-state. Singly or doubly frequency-selective pulses were used to generate either a J-modulated experiment (S) or a reference experiment (S _0). The combination of these two distinct experiments provides experimental data that, in favorable cases, are insensitive to incoherent relaxation effects, and which can be used to estimate long-range homonuclear J-couplings in multiple spin-systems. The concept is illustrated in the case of a uniformly ~(13)C and ~(15)N labeled sample of l-histidine, where the absolute value of homonuclear J-couplings between two spins separated by one, two or three covalent bonds are measured. Moreover, we show that a ~2J(~(15)N-C-~(15)N) coupling as small as 0.9 Hz can be precisely measured with the method presented here.