Rotating frame spin‐lattice relaxation experiments and the problem of intramolecular motions of peptides in solution

Abstract

SynopsisThe application of rotating frame spin-lattice relaxation to the determination of the intramolecular motions in peptides is discussed, and results are presented on the application of I3C 2' 1, to peptide microdynamics in solution. The effective molecular rotational reorientation times a t the amide and amino nitrogens may be derived from appropriate data on 2' 1, of the carbons adjacent to them. We also show by theoretical calculations that lH and I3C 2'1, experiments on suitable 2H and 15N substituted peptides will allow intramolecular main-and sidechain motions, characterized by times in the range 10-1-10-6 sec, to be investigated.

Mapping Protein Conformational Energy Landscapes Using NMR and Molecular Simulation

“…Dynamics on these timescales give rise to line‐broadening effects that can be probed using so‐called rotating frame relaxation or relaxation dispersion experiments 44. 45 Such methods, applied using one‐dimensional 1 H NMR, were originally used to study conformational equilibria in small biopeptides,46–49 and over the last two decades have been generalized for the study of 15 N‐ and 13 C‐labelled proteins50, 51 to probe molecular millisecond and microsecond exchange in the most challenging of experimental systems 52–54. Relaxation dispersion experiments are sensitive to weakly populated substates,55 and have been fundamentally important in probing the structure and dynamics of excited states that are invisible to most biophysical techniques, but which may be crucial for protein function 56…”

Nuclear magnetic resonance conformational studies on the chemotactic tripeptide formyl-L-methionyl-L-leucyl-L-phenylalanine. A small .beta. sheet

“…NMR Sample Preparation. As previously described, great care was taken to eliminate the well-known effects of introduced paramagnetic impurities and dissolved oxygen upon relaxation times (Bleich et al, 1976). The crystalline peptide resulting from the synthetic procedure described above was brought to pH 8 with NaOH in doubly glass-distilled H20, lyophilized, and then dried overnight in vacuo over P2Os at 50 °C.…”

“…NMR Techniques General. Our 100-MHz (>H) and 25.15-MHz (13C) NMR apparatus has been described previously (Bleich et al, 1976).…”

Conformational backbone dynamics of the cyclic decapeptide antamanide. Application of a new multiconformational search algorithm based on NMR data

“…They are sensitive to processes with exchange rate constants comparable to the applied rf field strength, = -yB\, provided the process modulates a nuclear resonance frequency. In the case of a two-site exchange process with the exchange time constant rex, with the populations p\ and p2 of the two conformers, and with the resonance frequency difference between the exchanging sites, one finds (Deverell et al, 1970;Bleich and Glasel, 1978) l/r"=l/T^+l/rlp6X 1+ , ( )2…”

“…These investigations are most sensitive to conformational dynamics when the rate constant is comparable either to the Larmor frequency, coo, to 2 , or to the radio frequency (rf) field strength, = -yBi. Measurements in the rotating frame are particularly convenient because the sensitive frequency window can be adjusted by selecting the rf field strength, B\ (Deverell et al, 1970; Bleich & Glasel, 1978). Several examples of motional processes in peptides have been investigated in this manner (Kopple et al, 1986(Kopple et al, , 1988.…”