TEMPERATURE DEPENDENCE OF PICOSECOND FLUORESCENCE KINETICS OF A CYANOBACTERIAL PHOTOSYSTEM I PARTICLE*

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Abstract
Picosecond time‐resolved fluorescence of photosystem I particles isolated fromSynechococcussp. was recorded in the wavelength range from 680 nm to 736 nm for temperatures of 6°C to 42°C and ‐ 100°C using the single‐photon‐timing technique. By global analysisofthe data we found four contributing lifetime components at the higher temperatures (T1' 12 ps,T1= 35 ps,T3' 65 ps,T4' 1000 ps). We attributeT1to an energy transfer between two pigment pools,T2to the charge separation process in the reaction center, componentT3is assigned to aggregate andT4to uncoupled chlorophyll emission. The corresponding decay‐associated spectra are presented. We also applied a target analysis procedure to fit parameters of a kinetic model directly to the data. The resulting rate constants and species‐associated spectra are discussed. The data indicate substantial spectral heterogeneity in the antenna with at least three substantially different chlorophyll pools. The overall exciton decay kinetics (by charge separation) is trap‐limited.

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