Light-induced damage of photosystem II primary electron donor P680: a high performance liquid chromatographic analysis of pigment content in D1/D2/cytochrome b559 complex under photoinhibitory conditions

By HPLC analytical method, the change of PS II RC's pigment content in the process of photodamage under strong illumination from spinach (Spinacia oleracea Mill.) was comparatively studied. The experimental results show that: (1) In authors' analytical conditions, (of which, [Chl] = 150 mu g/mL, and the illumination strength was put at 2.3 x 10(6) mJ.m(-2).s(-1)), 45 min of illumination could cause almost the whole loss of A680 in the fourth derivative absorption spectra, while A670 decreased to about one half of its original intensity; the absorption maximum in red, concurrently, was shifted from 676 nm to 671 nm, representing the loss of more than 90% of the photochemical activities of the PSII RC. (2) During the period of continuous illumination, the Chi concentration decreased in a 3-period style, which meant that the first [Chl] decreased to the 2/3 of its original amount from 20 min to 40 min after illumination had started, then became stabilized up to about 60 min of illumination, there after a second decrease of [Chl] in another about 20 min until it reached about 30% of the original level and remained unchanged from about 80 min on. The original pigment components of D1/D2/Cyt b559 was approximately as 6 Chl a:2 /Pheo:2 beta-Car which are in support of authors' previous proposal about the minimum Chl/Pheo ratio of 4:2 in PS II RC's pigment contents. (3) After about 40 min of illumination, a newly appeared elution peak was found between the Pheo and beta-Car peaks in HPLC profile, at the retention time of 7.2 min, a little later than that (6.9 min) of Pheo molecules, the newly appeared elution peak was supposed to be a kind of accumulated and stable product of the PSII RC's photodamage process and very much possible the Pheo-like molecules.