Chemical nature of monogenean sclerites. I. Stabilization of clamp-protein by formation of dityrosine

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Abstract
The clamp sclerites ofPricea multaeand other higher monogeneans was fuchsin-positive in Mallory's and Masson's triple stain, and the staining was not affected by detanning agents, suggesting some form of stabilization in the protein. The sclerites were positive in Millon's, Morner's and Xanthoproteic tests for aromatic amino acids, but negative in tests for sulphydryl and disulphide groups. Quinone, phenol and phenol oxidase were absent. They stained with basic dyes such as toluidine blue and methylene blue in the pH range of 3·5–9·5, and also exhibited bluish fluorescence in u.v. light which was not affected by lipid solvents, indicating the presence of dityrosine and recalling the protein present in the ligament cuticle of insects. These features indicate that the clampprotein is stabilized by the formation of dityrosine. It is suggested that this protein may be responsible for the biological properties of the clamp sclerites. This mode of stabilization by tyrosyl residues of the protein, resulting in the formation of dityrosine, is the first record of its kind to be reported in platyhelminths.