Singlet oxygen (1O2) is formed by triplet-triplet energy transfer from triplet chlorophyll to O2 via Type II photosensitization reaction in photosystem II (PSII). Formation of triplet chlorophyll is associated with the change in spin state of the excited electron and recombination of triplet radical pair in the PSII antenna complex and reaction center, respectively. Here, we have provided evidence for the formation of 1O2 by decomposition of protein hydroperoxide in PSII membranes deprived of Mn4O5Ca complex. Protein hydroperoxide is formed by protein oxidation initiated by highly oxidizing chlorophyll cation radical and hydroxyl radical formed by Type I photosensitization reaction. Under highly oxidizing conditions, protein hydroperoxide is oxidized to protein peroxyl radical which either cyclizes to dioxetane or recombines with another protein peroxyl radical to tetroxide. These highly unstable intermediates decompose to triplet carbonyls which transfer energy to O2 forming 1O2. Data presented in this study show for the first time that 1O2 is formed by decomposition of protein hydroperoxide in PSII membranes deprived of Mn4O5Ca complex.

• MeSH
• chlorofyl metabolismus   MeSH
• elektronová paramagnetická rezonance metody   MeSH
• fotosystém II (proteinový komplex) metabolismus   MeSH
• kyslík metabolismus   MeSH
• oxidace-redukce MeSH
• peroxid vodíku metabolismus   MeSH
• peroxidy metabolismus   MeSH
• přenos energie fyziologie   MeSH
• singletový kyslík metabolismus   MeSH
• světlo MeSH
• světlosběrné proteinové komplexy metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• chlorofyl MeSH
• fotosystém II (proteinový komplex) MeSH
• kyslík MeSH
• perhydroxyl radical MeSH Prohlížeč
• peroxid vodíku MeSH
• peroxidy MeSH
• singletový kyslík MeSH
• světlosběrné proteinové komplexy MeSH

When photosystem II (PSII) is exposed to excess light, singlet oxygen ((1)O(2)) formed by the interaction of molecular oxygen with triplet chlorophyll. Triplet chlorophyll is formed by the charge recombination of triplet radical pair (3)[P680(•+)Pheo(•-)] in the acceptor-side photoinhibition of PSII. Here, we provide evidence on the formation of (1)O(2) in the donor side photoinhibition of PSII. Light-induced (1)O(2) production in Tris-treated PSII membranes was studied by electron paramagnetic resonance (EPR) spin-trapping spectroscopy, as monitored by TEMPONE EPR signal. Light-induced formation of carbon-centered radicals (R(•)) was observed by POBN-R adduct EPR signal. Increased oxidation of organic molecules at high pH enhanced the formation of TEMPONE and POBN-R adduct EPR signals in Tris-treated PSII membranes. Interestingly, the scavenging of R(•) by propyl gallate significantly suppressed (1)O(2). Based on our results, it is concluded that (1)O(2) formation correlates with R(•) formation on the donor side of PSII due to oxidation of organic molecules (lipids and proteins) by long-lived P680(•+)/TyrZ(•). It is proposed here that the Russell mechanism for the recombination of two peroxyl radicals formed by the interaction of R(•) with molecular oxygen is a plausible mechanism for (1)O(2) formation in the donor side photoinhibition of PSII.

• MeSH
• chemické modely MeSH
• elektronová paramagnetická rezonance metody   MeSH
• fotochemie metody   MeSH
• fotosystém II (proteinový komplex) fyziologie   MeSH
• koncentrace vodíkových iontů MeSH
• kyslík chemie   MeSH
• propylgalan chemie   MeSH
• singletový kyslík * MeSH
• spin trapping metody   MeSH
• Spinacia oleracea MeSH
• světlo MeSH
• Synechococcus metabolismus   MeSH
• uhlík chemie   MeSH
• volné radikály MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• fotosystém II (proteinový komplex) MeSH
• kyslík MeSH
• propylgalan MeSH
• singletový kyslík * MeSH
• uhlík MeSH
• volné radikály MeSH