Rotational-echo double resonance of uniformly labeled 13C clusters

The use of rotational-echo double resonance NMR to measure distances from an observed tightly coupled cluster of C-13 spins to a distant N-15, P-31, or F-19 is practical if C-13 chemical shifts and homonuclear C-13-C-13 isotropic J interactions are refocused by a combination of rotor-synchronized C-13 pi and pi/2 pulses. This scheme is illustrated by experiments performed on diluted and recrystallized L-[C-13(3),N-15]alanine and L-[C-13(6),alpha-N-15]histidine. (C) 2003 Elsevier Science (USA). All rights reserved.