Rotational echo double resonance detection of cross-links formed in mussel byssus under high-flow stress

C-13{H-2} rotational echo double resonance NMR has been used to provide the first evidence for the formation of quinone-derived cross-links in mussel byssal plaques. Labeling of byssus was achieved by allowing mussels to filter feed from seawater containing L-[phenol-4-C-13]tyrosine and L-[ring-d(4)]tyrosine for 2 days. Plaques and threads were harvested from two groups of mussels over a period of 28 days. One group was maintained in stationary water while the other was exposed to turbulent now at 20 cm/s. The now-stressed byssal plaques exhibited significantly enhanced levels of 5, 5'-di-dihydroxyphenylalanine cross-links. The average concentration of di-dihydroxyphenylalanine cross-links in byssal plaques is 1 per 1800 total protein amino acid residues.