Laser Flash Photolysis of Eosin and Its Complex With Lysozyme

The transient absorption spectra of aqueous solutions of eosin and of the lysozyme‐eosin complex have been examined after excitation with a Q ‐switched frequency‐doubled (347 nm) ruby laser pulse. Eosin itself gives three broad, intense short‐lived absorption bands with maxima at wavelengths of 410, 460 and 580 nm, which other workers have identified with the semi‐reduced and semi‐oxidized radicals and the triplet state of the dye, respectively. In the complex with lysozyme, the yield and lifetime of the eosin triplet are greatly reduced in comparison with the free dye. It is suggested that excited eosin, when bound to lysozyme, decays mainly from the singlet state by pathways such as charge transfer which are not available to the free molecule.