Nejvíce citovaný článek - PubMed ID 16049789
Evidence for localisation of accumulated chlorophyll cation on the D1-accessory chlorophyll in the reaction centre of photosystem II
Accumulation of reduced pheophytin a (Pheo-D1) in photosystem II reaction center (PSII RC) under illumination at low redox potential is accompanied by changes in absorbance and circular dichroism spectra. The temperature dependences of these spectral changes have the potential to distinguish between changes caused by the excitonic interaction and temperature-dependent processes. We observed a conformational change in the PSII RC protein part and changes in the spatial positions of the PSII RC pigments of the active D1 branch upon reduction of Pheo-D1 only in the case of high temperature (298 K) dynamics. The resulting absorption difference spectra of PSII RC models equilibrated at temperatures of 77 K and 298 K were highly consistent with our previous experiments in which light-induced bleaching of the PSII RC absorbance spectrum was observable only at 298 K. These results support our previous hypothesis that Pheo-D1 does not interact excitonically with the other chlorins of the PSII RC, since the reduced form of Pheo-D1 causes absorption spectra bleaching only due to temperature-dependent processes.
- MeSH
- bakteriální proteiny chemie metabolismus MeSH
- fotosystém II (proteinový komplex) chemie metabolismus MeSH
- konformace proteinů účinky záření MeSH
- molekulární modely MeSH
- oxidace-redukce účinky záření MeSH
- sinice metabolismus MeSH
- spektrofotometrie metody MeSH
- světlo * MeSH
- vysoká teplota MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- bakteriální proteiny MeSH
- fotosystém II (proteinový komplex) MeSH
- photosystem II, psbA subunit MeSH Prohlížeč
Differential kinetic absorption spectra were measured during actinic illumination of photosystem II reaction centres and core complexes in the presence of electron acceptors silicomolybdate and ferricyanide. The spectra of samples with ferricyanide differ from those with both ferricyanide and silicomolybdate. Near-infrared spectra show temporary beta-carotene and peripheral chlorophyll oxidation during room temperature actinic illumination. Peripheral chlorophyll is photooxidized even after decay of beta-carotene oxidation activity and significant reduction of beta-carotene content in both reaction centres and photosystem II core complexes. Besides, new carotenoid cation is observed after about 1 s of actinic illumination in the reaction centres when silicomolybdate is present. Similar result was observed in PSII core complexes. HPLC analyses of illuminated reaction centres reveal several novel carotenoids, whereas no new carotenoid species were observed in HPLC of illuminated core complexes. Our data support the proposal that pigments of inner antenna are a sink of cations originating in the photosystem II reaction centre.
- MeSH
- beta-karoten metabolismus MeSH
- chlorofyl metabolismus MeSH
- ferrikyanidy metabolismus MeSH
- fotosyntéza MeSH
- fotosystém II (proteinový komplex) metabolismus MeSH
- hrách setý MeSH
- molybden metabolismus MeSH
- oxidace-redukce MeSH
- sloučeniny křemíku metabolismus MeSH
- světlo MeSH
- teplota MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- beta-karoten MeSH
- chlorofyl MeSH
- ferrikyanidy MeSH
- fotosystém II (proteinový komplex) MeSH
- hexacyanoferrate III MeSH Prohlížeč
- molybden MeSH
- silicomolybdate MeSH Prohlížeč
- sloučeniny křemíku MeSH
A multichannel kinetic spectrophotometer-fluorimeter with pulsed measuring beam and differential optics has been constructed for measurements of light-induced absorbance and fluorescence yield changes in isolated chlorophyll-proteins, thylakoids and intact cells including algae and photosynthetic bacteria. The measuring beam, provided by a short (2 micros) pulse from a xenon flash lamp, is divided into a sample and reference channel by a broad band beam splitter. The spectrum in each channel is analyzed separately by a photodiode array. The use of flash measuring beam and differential detection yields high signal-to-noise ratio (noise level of 2 x 10(-4) in absorbance units per single flash) with negligible actinic effect. The instrument covers a spectral range between 300 and 1050 nm with a spectral resolution of 2.1, 6.4 or 12.8 nm dependent on the type of grating used. The optical design of the instrument enables measuring of the difference spectra during an actinic irradiation of samples with continuous light and/or saturation flashes. The time resolution of the spectrophotometer is limited by the length of Xe flash lamp pulses to 2 micros.
