Surface accessibility of aromatic residues in human lysozyme using photochemically induced dynamic nuclear polarization NMR spectroscopy.

Resonances in the photo-CIDNP spectrum of human lysozyme have been assigned to specific spin systems despite extensive spectral overlap using the two-dimensional photo-CIDNP COSY experiment. Five of the 12 tyrosine, tryptophan and histidine residues of human lysozyme are found to be accessible to flavin dye in solution. This result is in good agreement with surface accessibility calculations carried out on the human lysozyme crystal structure. When amino acid differences are considered the photo-CIDNP results obtained for human lysozyme are in good agreement with results obtained previously for hen lysozyme.