INDIVIDUAL ASSIGNMENTS OF AMIDE PROTON RESONANCES IN THE PROTON NMR-SPECTRUM OF THE BASIC PANCREATIC TRYPSIN-INHIBITOR

Studies of proton-proton nuclear Overhauser effects were used to obtain individual assignments of 17 amide proton resonances in the 360 MHz proton NMR spectrum of the basic pancreatic trypsin inhibitor. First, optimizing the conditions for obtaining selective nuclear Overhauser effects in the presence of spin diffusion in macromolecules is discussed. Truncated driven nuclear Overhauser experiments were used to assign the amide proton resonances of the .beta.-sheet in the inhibitor. These techniques could serve quite generally to obtain individual resonance assignments in .beta.-sheet secondary structures of proteins. Combination of nuclear Overhauser studies with spin decoupling further resulted in individual assignments of the .gamma.-methyl resonances of the 2 isoleucines and numerous C.alpha. and C.beta. protons.