Primary-charge separation and excitation of chlorophyll a in photosystem II particles from spinach as studied by picosecond absorbance-difference spectroscopy

Direct observation of the immediate electron donor to chlorophyll‐a+II(P‐680+) in oxygen‐evolving photosystem II complexes Resolution of nanosecond kinetics in the UV

“…The observed signal rises with tie-90 = 1.2 ns ( fig.2, inset), corresponding to the time resolution of the apparatus. This indicates that QA is reduced in less than 1 ns, which is compatible with the time of a few hundred picoseconds found for the reoxidation of photo-reduced pheophytin, the presumed intermediate between Chl-an and QA [21,22].…”

Effects of hydrogen/deuterium exchange on photosynthetic water cleavage in PS II core complexes from spinach

“…The very fast relaxation observed in the 10 ns time domain was omitted because it does not reflect P680 +° reduction by Yz but originates from the remaining part of kinetics ascribed to Pheo-" oxidation by QA [27] and singlet state decay of chlorophylls [18]. Therefore, AA~°2'or(t) and AA~°jor(O) are the transient and initial amplitude, respectively, corrected for the contribution owing to these very fast reactions.…”

A well resolved ODMR triplet minus singlet spectrum of P680 from PSII particles

“…The main bleaching, to be assigned to the primary donor, peaks 680 nm while for large particles it does so at about 684 nm. In view of the previous P680'-P680 absorption difference spectra [8,19,20], it may be surprising to find P680 absorbing at such a long wavelength. However, most of the spectra mentioned are steady-state spectra which can be altered…”

“…The primary electron donor of PSI1 is associated with a spectral feature of 680 mn and is referred to as P680 [5,6]. A pheophytin molecule is known to act as an electron acceptor [7,8] in a light-induced charge separation which produces the radical pair P68O'Ph-. In *Corresponding author.…”