II. The photochemistry of proteins

Abstract

The examination of monolayers has been found to afford a quantitative method of investigation of the photochemical behaviour of many organic compounds of high molecular weight and appears to be especially suitable for macromolecular substances of physiological interest such as the proteins (Rideal 1932; Mitchell 1936 a , 1937 a ; Rideal and Mitchell 1937). The photochemical reactions occuring in the compounds spread in monolayers light, are observed by measurement of the changes in phase boundary potential and surface pressure; the light intensity is measured by chemical reference to proteins and related similar compounds, and, as a preliminary investing, the photochemical properties of the keto-imino linkage have been examined. The present work on the photochemistry of monolayers of typical proteins was undertaken from the point of view of radiation therapy, with the object of providing elementary data for interpretation of the biological actions of radiation. The investigation is quantitative and is accordingly limited to proteins for which the amino acid analyses are sufficiently complete, namely, wheat gliadin, zein, insulin and ovalbumin. The application of the analytic data to the interpration of the results of the photochemical experiments demands a detailed knowledge of the physical processes of light absorption in monolayers and of the photochemical significance of the absorption regard to the molecular configuration of the monolayers are necessary. The results of photochemical experiments on protein in bulk solution are required in the discussion of the chemical interpretation of the physical measurements on the monolayers.