Improved validation of IDP ensembles by one-bond C alpha-H alpha scalar couplings

Intrinsically disordered proteins (IDPs) are best described by ensembles of conformations and a variety of approaches have been developed to determine IDP ensembles. Because of the large number of conformations, however, cross-validation of the determined ensembles by independent experimental data is crucial. The (1)J(C alpha H alpha) coupling constant is particularly suited for cross-validation, because it has a large magnitude and mostly depends on the often less accessible dihedral angle psi. Here, we reinvestigated the connection between (1)J(C alpha H alpha) values and protein backbone dihedral angles. We show that accurate amino-acid specific random coil values of the (1)J(C alpha H alpha) coupling constant, in combination with a reparameterized empirical Karplus-type equation, allow for reliable cross-validation of molecular ensembles of IDPs.