Trolox, a Water-Soluble Analogue of α-Tocopherol, Photoprotects the Surface-Exposed Regions of the Photosystem II Reaction Center in Vitro. Is This Physiologically Relevant?
| Autor: | František Vácha, Heng Li, Sergio González-Pérez, Jorge Gutiérrez, Juan B. Arellano, Thor Bernt Melø, K. Razi Naqvi |
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| Rok vydání: | 2011 |
| Předmět: |
Photosynthetic reaction centre
Photosystem II Singlet oxygen Spectrum Analysis Trolox alpha-Tocopherol Peas Photosystem II Protein Complex chemistry.chemical_element Photochemistry Thylakoids Biochemistry Oxygen Scavenger chemistry.chemical_compound Reaction rate constant chemistry Photoprotection Vitamin E Chromans Methylene blue |
| Zdroj: | Digital.CSIC. Repositorio Institucional del CSIC instname |
| ISSN: | 1520-4995 0006-2960 |
| Popis: | Can Trolox, a water-soluble analogue of α-tocopherol and a scavenger of singlet oxygen (1O2), provide photoprotection, under high irradiance, to the isolated photosystem II (PSII) reaction center (RC)? To answer the question, we studied the endogenous production of 1O2 in preparations of the five-chlorophyll PSII RC (RC5) containing only one β-carotene molecule. The temporal profile of 1O2 emission at 1270 nm photogenerated by RC5 in D2O followed the expected biexponential behavior, with a rise time, unaffected by Trolox, of 13 ± 1 μs and decay times of 54 ± 2 μs (without Trolox) and 38 ± 2 μs (in the presence of 25 μM Trolox). The ratio between the total (kt) and chemical (kr) bimolecular rate constants for the scavenging of 1O2 by Trolox in aqueous buffer was calculated to be 1.3, with a kt of (2.4 ± 0.2) × 108 M–1 s–1 and a kr of (1.8 ± 0.2) × 108 M–1 s–1, indicating that most of the 1O2 photosensitized by methylene blue chemically reacts with Trolox in the assay buffer. The photoinduced oxygen consumption in the oxygen electrode, when RC5 and Trolox were mixed, revealed that Trolox was a better 1O2 scavenger than histidine and furfuryl alcohol at low concentrations (i.e. This work was funded by the Research Council of Norway (Project 191102), the Spanish Ministry of Science and Innovation (Grant BFU2007-68107-C02-02/BMC), and the Czech Ministry of Education (Project AV0Z50510513). J.B.A. is very grateful to the CSIC mobility program for funding his short-term visit to the Norwegian University of Science and Technology (PA1002668). |
| Databáze: | OpenAIRE |
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