[Comparative study of the photopotential and EPR signal arising after photooxidation of metal substituted pheophytins].

Ethanolic solutions of Zn-, Cd-Phe a and b and Chl a and b with p-benzoquinone as electron acceptor have been studied at pH 4. In all systems positive photopotentials and singlet ESR lines of the pigment cation radicals are observed. A conclusion is made that the photopotential is only partly attributable to an electrode reaction of the cation radicals, to a greater extent arising due to unknown, non-radical particles.