Abstract
Although it has been long known that proteins are subject to changes commonly called denaturation whereby their solubility is altered, our knowledge of the nature and the products of these changes is very limited.
The present study of the effects of dilute acids and alkalies on proteins originated from an observation made by one of us 1 some time ago, that serum proteins which had been dissolved in dilute NaOH solution gave more color with the phenol reagent of Folin and Denis than the same proteins which had not been dissolved in NaOH. With the hope of developing a method based on this observation for the differentiation of proteins, a study of the change in chromogenic value of a number of proteins, both in HC1 and in NaOH solutions, was undertaken. Changes of chromogenic value were observed in so dilute solutions of acids and alkalies that no question of the decomposition of the protein could arise, and it occurred to us that the phenomenon under observation may be related to the process of denaturation of proteins. Since there has been no investigation on this subject in recent years, it has seemed desirable to study not only the change in chromogenic value but also other effects which dilute acids and alkalies may have on proteins.
We have studied the problem from three points of view:
1. Change of solubility as evidenced by the formation of a precipitate upon neutralizing the solution.
2. Increase in the amount of color obtained when a definite amount of the protein solution is allowed to react with the phenol reagent of Folin and Denis in the presence of sodium carbonate.
3. Liberation of non-protein substances which can be determined after the removal of the protein.
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