Photoperoxidation in isolated chloroplasts

摘要: Abstract A photo-induced cyclic peroxidation in isolated chloroplasts is described. In an osmotic buffered medium, upon illumination produce malondialdehyde (MDA)—a decomposition product of tri-unsaturated fatty acid hydroperoxides—bleach endogenous chlorophyll, and consume oxygen. These processes show ( a ) no reaction the absence illumination; b initial lag phase 10–20 minutes duration; c linear which rate proportional to square root light intensity; d cessation occurring within 3 after ceases; e termination several hours illumination. The kinetics above fit equation with velocity coefficients near those for chemical peroxidation. stoichiometry MDA/O 2 = 0.02, O Chl bleached 6.9 correlates well MDA production efficiency other biological systems molar ratio unsaturated acids chlorophyll. energies activation phases are 17 0 kcal/mole, respectively, same as that autoxidation. During oxygen uptake dependence temperature concentration indicates during reaction, tension at site 100-fold lower than aqueous phase. It concluded can undergo initiated by absorbed Photoperoxidation results destruction chlorophyll chloroplast membranes.