Abstract
FROM a study of the elastic properties of wool fibres in solutions of varying hydrogen ion concentration, Speakman1 has argued that the long peptide chains of wool are bridged by salt linkages formed from the acid side chains of aspartic and glutamic acids, and the basic side chains of arginine, lysine and histidine. In addition, chemical equivalence between the free acid and basic side chains was deduced from the form of the curve relating the ease of fibre extension to the pH of the medium. Such is the salt linkage theory, for which support was later found in the titration curves of wool2 and feather keratins3, as well as in deductions concerning the influence of the salt linkages on the reactivity of the disulphide bond in strained animal fibres4. Unfortunately, however, the amounts of aspartic and glutamic acids isolated from wool and goose feather by Abderhalden5 are insufficient to account for the basic side chains as well as amide nitrogen. The difficulties of protein analysis are so great that the salt linkage theory is not called into question by Abderhalden's results, but it was felt desirable to augment the supporting evidence already available by direct proof based on new determinations of the dicarboxylic acids in wool and seagull quill, which may be regarded as typical keratins.
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References
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SPEAKMAN, J., TOWNEND, F. Constitution of the Keratin Molecule. Nature 139, 411 (1937). https://doi.org/10.1038/139411b0
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DOI: https://doi.org/10.1038/139411b0
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