Desmosine and isodesmosine as cross-links in the hinge-ligament protein of bivalves. 3,3'-Methylenebistyrosine as an artefact.

Desmosine and isodesmosine were detected in an invertebrate molluscan species, i.e. in an insoluble protein in the hinge ligament of a bivalve species, Sakhalin surf clam (Pseudocardium sachalinensis, in family Mactridae). The protein is rich in glycine and methionine S-oxide but devoid of hydroxyproline and hydroxylysine. 3,3'-Methylenebistyrosine was also detected in the HCl hydrolysate of the hinge-ligament protein, but it was found to be an artefact produced from tyrosine and formaldehyde derived from methionine S-oxide during the HCl hydrolysis of the protein.