Protein backbone (15)N relaxation rates as a tool for the diagnosis of structure quality

In the work reported herein we define a structure validation factor that depends on protein backbone (15)N relaxation rates. This is an alternative method to the previously defined quality factors derived from anisotropic chemical shifts or residual dipolar couplings. We have used the structure dependence of (15)N relaxation rates of anisotropically tumbling proteins to calculate this structure diagnosis factor and have used it to demonstrate the improvement of protein structures refined with residual dipolar couplings.