Formation of radicals from singlet oxygen produced during photoinhibition of isolated light-harvesting proteins of photosystem II

Abstract

Electron spin resonance spectroscopy and liquid chromatography have been used to detect radical formation and fragmentation of polypeptides during photoinhibition of purified major antenna proteins, free of protease contaminants. In the absence of oxygen and light, no radicals were observed and there was no damage to the proteins. Similarly illumination of the apoproteins did not induce any polypeptide fragmentation, suggesting that chlorophyll, light and atmospheric oxygen are all participating in antenna degradation. The use of TEMP and DMPO as spin traps showed that protein damage initiates with generation Of O-1(2), presumably from a triplet chlorophyll, acting as a Type II photosensitizer which attacks directly the amino acids causing a complete degradation of protein into small fragments, without the contribution of proteases. Through the use of scavengers, it was shown that superoxide and H2O2 were not involved initially in the reaction mechanism. A higher production of radicals was observed in trimers than in monomeric antenna, while radical production is strongly reduced when antennae were organized in the photosystem 11 (PSII) complex. Thus, monomerization of antennae as well as their incorporation into the PSII complex seem to represent physiologically protected forms. A comparison is made of the photoinhibition mechanisms of different photosynthetic systems. (C) 2003 Elsevier B.V. All rights reserved

Early Transcriptional Defense Responses in Arabidopsis Cell Suspension Culture under High-Light Conditions

“…The main sites of 1 O 2 production are chlorophyll-containing photosynthetic complexes and the reaction center of PSII (Rinalducci et al, 2004;Krieger-Liszkay et al, 2008). By contrast, 1 O 2 does not seem to be produced at any significant level in PSI .…”

A comparative study of fluorescent singlet oxygen probes in plant leaves

“…Although 1 O 2 is probably the primary ROS product, other ROS have also been identified in photosynthetic tissues under PI. These include various oxygen-and carbon-centred radicals [23,[38][39][40][41][42][43]. Using TEMPO-9-AC as a broad-range radical probe, we attempted to trap radicals in PIexposed leaves.…”

Phototoxicity of Kava — Formation of Reactive Oxygen Species Leading to Lipid Peroxidation and DNA Damage

“…With concomitant exposure to UVA light for 20 sec, singlet oxygen was generated, as evidenced by an ESR spectral profile which is typical of TEMPO (Fig. 6) (Rinalducci et al, 2004). The intensity of these ESR signals progressively enhanced when photoirradiation time increased from 0 to 20, 70, 120, 180, 240, and 300 sec, respectively.…”

“…The specific ESR spin trapping agent of singlet oxygen, TEMP (Rinalducci et al, 2004), was employed to investigate whether the UVA irradiation of kava extract generates singlet oxygen species. ESR instrument settings were as follows: 20 mW microwave power, 100 G sweep width, 1 G field modulation amplitude, and 100 kHz modulation frequency.…”