χ1 Rotamer Populations and Angles of Mobile Surface Side Chains Are Accurately Predicted by a Torsion Angle Database Potential of Mean Force

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Abstract
The equilibirum angles and distributions of χ1 rotamers for mobile surface side chains of the small, 63-residue, B1 domain of protein L have been calculated from the static crystal structure by rigid body/torsion angle simulated annealing using a torsion angle database potential of mean force and compared to those deduced by Monte Carlo analysis of side chain residual dipolar couplings measured in solution. Good agreement between theory and experiment is observed, indicating that for side chains undergoing rotamer averaging that is fast on the chemical shift time scale, the equilibrium angles and distribution of χ1 rotamers are largely determined by the backbone φ/ψ torsion angles.