Half-filter experiments for assignment, structure determination and hydration analysis of unlabelled ligands bound to 13C/15N labelled proteins

A novel variant of the C-13/N-15 omega(2) half-filter experiment is reported for studying the hydration of an unlabelled ligand bound to a N-15 and C-13 uniformly labelled biological macromolecule. This doubly tuned filter experiment represents a powerful tool for obtaining resonance assignments, structure determination and hydration properties of a ligand. Its application to the binary complex formed by the inserted-domain (I-domain) of the leukocyte function-associated antigen-1 (LFA-1) with a ligand reveals the presence of H2O molecules at the binding interface.