Time and spectral resolved phosphorescence of singlet oxygen and pigments in photosystem II particles

Singlet oxygen generated via chlorophyll triplets in photosynthetic systems can destroy basic components of photosynthetic apparatus. In order to study this process a sensitive spectroscopic experimental set-up was built to detect both weak infrared (IR) chlorophyll phosphorescence (between 900 and 1000 nm) and singlet oxygen phosphorescence (at 1270 nm). The spectral and time resolution of the used monochromator and photon counting multiscaler are sufficient to provide two-dimensional matrix of temporally and spectrally resolved IR luminescence data. We have studied IR emission of photosystem II particles in D2O and H2O buffer including the effect of the sodium dodecyl sulphate (SDS) detergent. Both sub-microsecond lifetime of chlorophyll triplet states and microsecond lifetime of singlet oxygen were determined. The singlet oxygen lifetime in D2O (of 18 μs) was approximately five times longer than that in H2O. Quantum efficiency of singlet oxygen generation in photosystem II particles was significantly lower than that in chlorophyll a in acetone, however, it could be substantially increased by addition of SDS.