Direct refinement against proton-proton dipolar couplings in NMR structure determination of macromolecules

The computational tools necessary for making use of (1)H-(1)H dipolar couplings in macromolecular structure refinement are presented. Potentials are described for direct refinement against (1)H-(1)H dipolar couplings of known sign as well as of unknown sign. In addition, a multiple potential is developed for prochiral protons whose stereospecific assignments are unknown. The utility of direct (1)H-(1)H dipolar coupling refinement is illustrated using the small protein ubiquitin. It is shown that direct (1)H-(1)H dipolar coupling refinement leads to improvements in the precision, accuracy, and quality of the resulting structures.