End-group assay in some proteins of the keratin-myosin group

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Abstract
Sanger''s fluorodinitrobenzene method was applied to a study of the terminal amino groups in tropomyosin, myosin and fibrinogen. Tropomyosin and myosin appear to consist of cyclopeptides. It is not yet possible to decide whether the terminal residues in fibrinogen arise from the protein itself or from impurities. The lysine side chains in myosin are fully reactive. There is evidence that tropomyosin contains a small proportion of unreactive lysine side chains, and the same is true of fibrin but not of fibrinogen. The end-group method has been used to investigate the stability of the peptides bonds of these proteins in acid and alkaline media. Myosin at 0[degree] is stable to alkali at pH 11 but not at pH 13; tropomyosin is stable up to pH 12.
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