NMR relaxation times provide a window into the amplitudes and energetics of local motions which can be important in determining molecular function. Solid state NMR methods make it possible to follow these dynamics over wide temperature ranges and without the complication of overall molecular tumbling. We have been successful in developing a theoretical framework that fully accounts for the temperature dependence of C-13 T1 times of methyl groups in solid peptides, and has been extended to measuring the distribution of picosecond amide NH correlation times in a protein. A particularly interesting aspect of this work is the interplay between spin diffusion and magic angle spinning. The plot in the masthead above depicts an unexpectedly rapid rise in the N-15 T1 with MAS frequency in a model peptide. A new spin diffusion mechanism named CSA enable spin diffusion has been shown to explain this observation. Current work is aimed at exploiting this effect to detect long range distance constraints.
distribution of NH correlation times in ubiquitin at -10 C