Abstract: | The data now at hand show that specificity among biologically active peptides is probably not as exquisite as might have been deduced from experiences with some of the water-soluble vitamins. It is plain that a given biological effect can be evoked by peptides which differ considerably. It is likewise plain that the effect cannot be evoked by a number of other peptides. There is apparently some specificity, but more is involved than that incorporated in the classical view. |