In situ analysis of peptidyl DOPA in mussel byssus using rotational-echo double-resonance NMR

Rotational-echo double-resonance (REDOR) C-13 NMR spectra with H-2 dephasing have been obtained from plaques and threads from the byssus of the marine mussel Mytilus edulis labeled by sea-water exposure to L-[ring-4-C-13]tyrosine and L-[ring-d(4)]tyrosine for 2 days. Specific isotopic enrichment of tyrosine in protein reached 25% in both C-13 and H-2. Fifteen percent of the total C-13 label was incorporated as diphenolic carbon. Based on REDOR dephasing, about one-tenth of tyrosine rings in both intact plaques and threads are within 4 Angstrom of each other or rings of 3,4-dihydroxyphenylalanine (DOPA). However, there is no direct evidence for the formation of covalent linkages between or among tyrosine and DOPA rings in either plaques Or threads. (C) 1996 Academic Press, Inc.