An ESEEM study of the oxidized electron donor of plant photosystem II: Evidence that D is a neutral tyrosine radical
✍ Scribed by R.G. Evelo; A.J. Hoff; S.A. Dikanov; A.M. Tyryshkin
- Publisher
- Elsevier Science
- Year
- 1989
- Tongue
- English
- Weight
- 560 KB
- Volume
- 161
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
Electron spin-echo envelope modulation (ESEEM) has been performed on the tyrosyl radical D' in photosystem II of plants and algae. This radical was investigated in PS II-enriched subchloroplast particles, and in perdeuterated and "N-substituted ChloreNa uulgaris algae. From the ESEEM analysis in the time and frequency domain, two proton hyperfine interactions were determined. One of these protons has hyperfine parameters &,=27.2 MHz, T,, = -3.1 MHz and TZ2/T,, =0.5. The second proton, which is easily exchangeable by deuterium, has parameters ai,,,= a 1.6 MHz, T1 1 = 7 8.4 MHz and T,,/T, , = 1, The hyperfine parameters of the first proton are characteristic of a bmetbylene proton, whereas those of the second indicate that it is a proton hydrogen bonded to the tymsyl oxygen. We conclude that the oxidized tyrosyl donor is a neutral hydrogen-bonded radical.