ON EXCITATION OF BIOLOGICAL SUBSTANCES

Abstract

Fluorescent and phosphorescent spectral data, kinetic studies (including order of reaction), lifetimes, and activation-energy considerations are presented for a wide variety of biological compounds and the dyes acridine yellow and acridine orange. Results indicate that electronic transitions involving singlet-triplet intercombinations are functional in these compounds. The marked optical changes observed in freezing aqueous solutions, namely, the shift from fluorescence to phosphorescence, appear to be a universal property of fluorescent materials.