Kinetics of reduction of the oxidized primary electron donor of Photosystem II in spinach chloroplasts and in Chlorella cells in the microsecond and nanosecond time ranges following flash excitation

High‐resolution triplet‐minus‐singlet absorbance difference spectrum of photosystem II particles

“…The origin of this band in the T-S spectra of P-700 is unclear. It is also seen in the P+-700 -P-700 and in the P+-680 -P-680 absorbance difference spectra [25,26], and weak bands around 800 nm are observed in the absorbance difference spectra of chl a+ and chl a-in vitro [27,28], but not in that of 'Chl a 1291. Possibly the 820 nm band is due to a charge transfer contribution, which then is weaker in the triplet of the PS II particles.…”

Isolation of a photosystem 2 preparation from higher plants with highly enriched oxygen evolution activity

“…A very fast (30 ns) reduction of P680f in darkadapted chloroplasts which they associated with the oxygen evolving system was detected in [3]: it was shown that hydroxyl~ine abolished the very fast kinetics and allowed the detection of P680+ in the ms time-range. From our experiments with the PS2 preparation at pH 6, we estimate that only 40-50% of the total P680+ is reduced with submicrosecond kinetics under repetitive flash conditions where oxygen evolution is occurring.…”

“…The amplitude and kinetics of the reduction of P680+ in the Triton X-100 PS2 preparation has been measured by following rapid absorption changes at 820 nm as in [3,4]. Fig.4a shows the absorption change which occurs under conditions where oxygen is actively being evolved by the preparation.…”

“…From our experiments with the PS2 preparation at pH 6, we estimate that only 40-50% of the total P680+ is reduced with submicrosecond kinetics under repetitive flash conditions where oxygen evolution is occurring. The origin of the slower phases in P680+ reduction are under investigation at present, The slower kinetics may be due to a fast back-reaction from Q [3,4], or possibly an alternative pathway for the donation of electrons to P680+.…”

Primary Processes of Photosynthesis: Structural and Functional Aspects

“…that there is an intermediate of unknown chemical nature between plastocyanin and P700'. As far as electron donation to P680' is concerned, a major step forward has been made by Van Best and Mathis [69]. They have constructed a low noise flash absorption photometer and have been able to demonstrate that with dark treated systems the reduction of P680' takes place with a t , of about 30ns.…”