Photophosphorylation in stable chloroplast fragments from the alga Chlamydomonas reinhardi

Abstract

Stable chloroplast fragments exhibiting high reproducible rates of photophosphorylation and good coupling ratios can be obtained from the alga Chlamydomonas reinhardi using a simple procedure based on brief sonication of young cells in a medium of high osmolarity containing serum albumin. Chloroplast fragments prepared by this method exhibit long-term stability; Hill activity remains constant for at least 26 h while cyclic and non cyclic photophosphorylation activities exhibit a half time stability constant of about 24 h. Chloroplast fragments isolated by this method are insensitive to uncoupling of photophosphorylation by ammonium chloride. It is suggested that in the presence of ammonium chloride membrane potential may act as the driving force for photophosphorylation.