Analysis of deuterium relaxation-derived methyl axis order parameters and correlation with local structure

Methyl axis (S-axis(2)) and backbone NH (S-NH(2)) Order parameters derived from eight proteins have been analyzed. Similar distribution profiles for Ala S-axis(2) and S-NH(2) Order parameters were observed. A good correlation between the two S-axis(2), values of Val and Leu methyl groups is noted, although differences between order parameters can arise. The relation of S-axis(2), or S-NH(2) to solvent accessibility and packing density has also been investigated. Correlations are weal;, likely reflecting the importance of collective, non-local motions in proteins. The lack of correlation between these simple structural parameters and dynamics emphasizes the importance of motional studies to fully characterize proteins.