Leucine Side-Chain Conformation and Dynamics in Proteins from 13C NMR Chemical Shifts

In summary, it is demonstrated here that the 13C NMR γ-gauche effect gives rise to a pattern of leucine methyl chemical shifts that are sensitive to conformation and dynamics; this demonstrates the potential of chemical shift information as an intelligible source of protein structure and a quantitative measure of the extent of averaging around intervening dihedral angles. The temperature dependence of the methyl 13C chemical shift difference provides additional information about the relative energies of the interconverting side-chain conformations. This information is the key to interpreting side chain dynamics from spin relaxation data, and may be a valuable restraint on side-chain conformation in ensemble or time-average structure refinement protocols. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.