Collective protein dynamics and nuclear spin relaxation

Theoretical methods are developed and applied to the protein crambin as a model system to characterize collective normal mode dynamics and their effects on correlations between torsion angle fluctuations and heteronuclear NMR relaxation parameters. Backbone N–H NMR S2 order parameters are found to be predominantly determined by local φ and ψ torsion angle fluctuations induced by collective protein modes. The ratio between Cβ–Hβ and Cα–Hα order parameters directly yields fluctuation amplitudes of the sidechain χ1 torsion angles. The results allow a more direct interpretation of motional effects monitored by nuclear spin relaxation.