Delineation of conformational dynamics in solution from 1H and 3H nuclear magnetic resonance spin–lattice relaxation rates

Abstract

Nuclear magnetic resonance relaxation analysis has been carried out on ¹H and ³H nuclei within the succinyl moiety of the following tripeptides: (i) succinyl-L-Prolyl-L-alanine: (ii)[2,3–²H]-succinyl-L-prolyl-L-alanine; (iii)[2,3–³H]-succinyl-L-prolyl-L-alanine. ¹H–¹H and ³H–³H dipolar relaxation terms were evaluated by measuring non-selective, single-selective and double-selective spin–lattice relaxation rates, yielding complete delineation of motional and conformational features. Rotamer fractional populations were calculated and used for unambiguously assigning all J couplings. Correlation times for both principal and internal reorientational motions could be evaluated at 0.33 and 0.09 ns, respectively, at 298 K. ³H n.m.r. relaxation investigations were shown to provide a very suitable aid to delineation of conformational dynamics in solution.