Frontal analysis studies on the adsorption of crystalline egg albumin and its cleavage products

Abstract

1. 1. The possibility of using frontal analysis on activated carbon in order to determine the composition of amino acid mixtures has been investigated. It has been found that the Langmuir isotherm can be used and that the adsorption displacement can be conpensated for by using certain formulas. Binary and ternary mixtures of amino acids have been studied and their composition has been determined with fair accuracy. The conclusions drawn from these experiments served as a guide for the subsequent investigation of unknown peptide mixtures obtained from the hydrolysis of egg albumin. 2. 2. Crystalline egg albumin and the products obtained from partial hydrolysis of crystalline egg lbumin with pepsin have been investigated by frontal analysis on aluminium hydroxide (Mataki gel) and on carbon. The cleavage products are obtained separately by using the first mentioned adsorbent, and the unchanged protein by using the second. The ratio of amino nitrogen to total nitrogen of the different fractions and the split percentage have been calculated for different digestion times. Concerning the breakdown process of the egg albumin the following was concluded. Only part of the protein molecules are attacked at first and intact protein is observed until the very end of the reaction. The cleavage products at the beginning consist of deca or higher peptides but at the end tripeptides are the average constituents. 3. 3. The fraction containing the cleavage products only (peptide fraction) was investigated by frontal analysis on carbon and the composition determined in the same way as for the amino acid mixtures mentioned above. The number of fractions observed was less than five. The component with the lowest adsorption had the highest ratio of amino nitrogen to total nitrogen. In the earliest stages only fairly large products seemed to be formed, while in the final mixture even some dipeptides were indicated. 4. 4. The peptide fractions were investigated with paper chromatography, showing more fractions than could be detected on carbon. No amino acids seemed to be present. After complete hydrolysis with strong hydrochloric acid, the fractions were again investigated on paper. The amino acids in the fraction showing the lowest adsorption on carbon were mostly amino acids that themselves show low adsorption on carbon. The lower peptides are accordingly mainly made up of glutamic and aspartic acid, glycine, valine, alanine, and leucine.