The effects of 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone on isolated pea chloroplasts

The effects of a quinone analogue, 2,5-dibromo-3-methyl-6-isopropyl-p-benzoquinone(DBMIB), on the photochemical activities of isolated pea chloroplastshave been investigated. DBMIB completely inhibits pseudo-cyclicflow with methyl viologen (MV) and partially inhibits non-cyclicflow with ferricyanide (FeCN) in both coupled and uncoupledsystems. It is also shown that, under some circumstances, DBMIBacts like an uncoupler in that it stimulates electron flow andinhibits cyclic photophosphorylation. ¹ Present address: 32(1), 6 1/4 Mile, Prome Road, Kamayut P.O., Rangoon, Burma. (Received May 21, 1973; )