Direct refinement against proton-proton dipolar couplings in NMR structuredetermination of macromolecules

The computational tools necessary for making use of H-1-H-1 dipolar couplin gs in macromolecular structure refinement are presented. Potentials are des cribed for direct refinement against H-1-H-1 dipolar couplings of known sig n as well as of unknown sign. In addition, a multiple potential is develope d for prochiral protons whose stereospecific assignments are unknown. The u tility of direct H-1-H-1 dipolar coupling refinement is illustrated using t he small protein ubiquitin. It is shown that direct H-1-H-1 dipolar couplin g refinement leads to improvements in the precision, accuracy, and quality of the resulting structures.