Improved Estimation of Protein Rotational Correlation Times from 15 N Relaxation Measurements

Abstract

In the study of protein backbone dynamics by 15 N relaxation measurements, an initial estimation of the isotropic global correlation time, τ m , is usually obtained from the average T 1 /T 2 ratio of nuclear spins that do not exhibit slow internal motion and with T 2 values not significantly shortened by chemical or conformational exchange processes. Different methods have been used for identification of the rates of internal motion. However, the number of nuclear spins included in the τ m estimation is often larger than the number that ultimately can be fitted to a single-order parameter, S 2 , implying that some nuclear spins involved in the initial τ m estimation actually have an effectiv..