Studies on the relation between the fast phase of millisecond delayed light emission and the proton released from oxidation of water in spinach chloroplast

The relation between the fast phase of ms-DLE (delayed light emission measu red with a phosphoroscope) and the proton released from water oxidation in spinach chloroplasts was studied in several aspects. When photophosphorylat ion was allowed to be coupled to the Hill reaction the intensity of the fas t phase of ms-DLE of chloroplast was lowered more at 1 degrees C than at 25 degrees C, and the photophosphorylation rate within 40 ms of hashing light was higher at 1 degrees C than at 25 degrees C. Adding the epsilon subunit of ATP synthase to the chloroplast preparation to block the leakage of pro tons through ATP synthase, the intensity of the fast phase of ms-DLE was en hanced, to a larger extent at 1 degrees C than at 25 degrees C. When the ms -DLE was measured under isotonic conditions, the intensity of fast phase of ms-DLE enhanced by proton released from oxidation of water was more pronou nced. The above results support the suggestion that under lower temperature and isotonic conditions, the proton released from water oxidation was liab le to be localized and could enhance the intensity of the fast phase of ms- DLE more effectively.