Abstract
McChesney and Miller 1 introduced the use of liquid ammonia as a medium for the study of the chemical properties of proteins. They found that proteins were acidic in liquid ammonia and that when they were treated with alkali metals at −33.5°C. or with ammono bases at 80-120°C. for 48-72 hours, they are partially ammonolyzed. We have reported 2 a study of the liberation of hydrogen when sodium is added to liquid ammonia solutions or suspensions of silk fibroin, diketopiperazine, glycyl-alanine, n-methylacetamide, glycollic acid, acetanilide, tyrosine, and alanine. This report includes the results of further investigation on silk fibroin, diketopiperazine, and dipeptides, and investigations on casein, egg albumin and edestin. A chemical examination of the products formed will be carried out later.
When the quantity of hydrogen liberated by a sample of protein, such as silk-fibroin 20 and egg albumin having a definite nitrogen content is plotted against the quantity of sodium added, the curve may be divided into 3 distinct parts.
The first part of the curve is characterized either by absorption of sodium by the protein or by the efficient absorption of hydrogen by one part of the protein molecule following the liberation of hydrogen by sodium from another part of the molecule, or both. Any of these events involves reduction of some part of the protein molecule. When 2 sodium atoms are added for each 4 nitrogen atoms, the reduction is equivalent to the addition of 2 hydrogen atoms. The second part of the curve covers a range in which the quantity of hydrogen liberated approximately parallels the quantity of sodium added.
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