A N-15-FILTERED 2D H-1 TOCSY EXPERIMENT FOR ASSIGNMENT OF AROMATIC RING RESONANCES AND SELECTIVE IDENTIFICATION OF TYROSINE RING RESONANCESIN PROTEINS - DESCRIPTION AND APPLICATION TO PHOTOACTIVE YELLOW PROTEIN

A new method to selectively detect the ring resonances of the aromatic residues in N-15-labelled proteins is presented. The experiment consi sts of a 2D H-1 TOCSY sequence with removal of the amide signals via N -15-filtering. Experiments are acquired in the absence and presence of water inversion; combining the two spectra allows selective observati on of the tyrosine ring resonances and enables the identification of t heir delta and epsilon ring protons. The experiment is demonstrated on a N-15-labelled sample of Photoactive Yellow Protein and is shown to give good selectivity for tyrosine ring resonances under a wide range of temperatures and pH values.