A fundamental problem of modern biologic science is the elucidation of the structure of proteins. An increasing number of biologically important substances have been demonstrated to be proteins.1 Several enzymes have been isolated in crystalline form, and each of these has been found to be a protein. Several of the hormones are also now known to be proteins or protein derivatives. More recently has come the astounding demonstration that crystalline proteins of high molecular weight can be isolated from infected plant tissues and that these proteins have a physiologic activity identical with that attributed to an infectious virus.
The proteins resemble one another in that all proteins on hydrolysis yield the same amino acids, although proteins may vary widely with respect to the number of these fundamental units and the quantity of each which may be present in their molecules. Nevertheless the close resemblance among the products of complete
STRUCTURE OF PROTEINS. JAMA. 1938;111(23):2120–2121. doi:10.1001/jama.1938.02790490050015
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