A Study of the Action of Ketene on Proteins

Authors

Earl Burdette Barnes, University of Nebraska-Lincoln

Document Type

Thesis

Date of this Version

6-1940

Citation

Thesis (M.A.)—University of Nebraska—Lincoln, 1940. Department of Chemistry.

Comments

Copyright 1940, the author. Used by permission.

Abstract

With the growing importance of ketene in protein chemistry in view, this study was undertaken in an attempt to correlate the action of this reagent on some simple well known proteins, with that which is known about the action of the ketene on amino acids.It was thought that such a study might lead to a method of classifying proteins on a basis of reactivity.It later developed that the study of these fundamental correlations cast serious doubt on the conclusions reached by the workers in protein chemistry mentioned previously.

A description has been given of the construction of a satisfactory ketene generator, with modifications that make for greater convenience in utilization of ketene as an acetylating agent.

1. A method for obtaining zein in neutral and alkaline aqueous solutions has been devised, which should be of considerable value in further work with this protein.

2. Representative proteins, i.e., crystalline egg albumin, edestin, gelatin, casein, and zein, have been treated with ketene under different conditions of pH, and a description of the resulting products have been given.

3. It has been shown that available specific colorimetric reagents for tyrosine such as Millon’s reagent and the Folin’s phenol reagent are of no value for differentiating the free and the acetylated phenolic hydroxyl group in this molecule.

4. The rate of acetylation of the α-amino group of glycine in alkaline solution has been known to be at least twice the rate of acetylation in acid solution. Experimental proof has been given for the relation of this to the Zwitterian equilibrium by treatment of solutions containing the ammonium ion with ketene.

5. Both the phenolic hydroxyl of tyrosine and the 2,5 diketopiperazine molecule have been shown to be unaffected by ketene in acid solution.

6. A criticism of Herriott’s analytical methods in his work on treatment of pepsin with ketene has been made.

Advisor: W. E. Militzer