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
Abstract: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 µg/mL, and the illumination strength was put at 2.3 ×10 6 mJ·m－2·s－1 ), 45 rain 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 PS Il RC. (2) During the period of continuous illumination, the Chl 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 rain 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:2β-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 andβ-Car peaks in HPLC profile, at the retention time of 7.2 min, a little later than that (6.9 rain) of Pheo molecules, the newly appeared elution peak was supposed to be a kind of accumulated and stable product of the PS II RC‘s photodamage process and very much possible the Pheo-like molecules.