Page:Popular Science Monthly Volume 72.djvu/400

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say is that there appears to be some kind of linkage between certain groups in the proteid molecules which is not uncoupled by the enzymes in the body, and that when it is uncoupled, as in acid hydrolysis, then it is impossible for it to be coupled up again in the body. This combination, which the cells can neither take to pieces nor put together again, must be present, in order that the other component parts of the proteid molecule may gather about them and group themselves round them when the synthesis of proteids is to occur. These considerations appear to suggest that the synthetic processes here involved may be the work of the same agent as the hydrolytic, the limitations in its hydrolytic power determining the limitations of its synthetic activity, as in reversible zymolysis.

Whether this conception of the matter is wholly correct we can not say, but at all events it is a suggestion as plausible as any that can be offered at the present time.

Just here we may advantageously consider the nature and proportion of the chemical components present in the protein molecule so far as has been ascertained by hydrolysis with acids. Recently, much work has been done on this subject, especially by Dr. Thomas B. Osborne at New Haven. The accompanying table gives the results with eight typical proteins from the animal and vegetable kingdoms, which may be taken as representative of the present state of knowledge.

Percentage Yield of Cleavage Products[1][2]

PSM V72 D400 Percentage yield of cleavage products.jpg
All the above data from vegetable proteins were furnished by Dr. Thomas B. Osborne and represent his own work and that of his co-workers.

Perhaps the most impressive fact, certainly the one most quickly discernible, is that a large fraction of the protein molecule, 28-50

  1. Emil Fischer, P. A. Levene and R. H. Aders.
  2. Aberhalden. Cow's milk.