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. 1981 Feb;78(2):957–961. doi: 10.1073/pnas.78.2.957

Energies and kinetics of radical pairs involving bacteriochlorophyll and bacteriopheophytin in bacterial reaction centers

Vladimir A Shuvalov 1,†, William W Parson 1
PMCID: PMC319924  PMID: 16592980

Abstract

Absorbance changes reflecting the formation of a transient radical-pair state, PF, were measured in reaction centers from Rhodopseudomonas sphaeroides under conditions that blocked electron transfer to a later carrier (a quinone, Q). The temperature dependence of the absorbance changes suggests that PF is an equilibrium mixture of two states, which appear to be mainly 1[P[unk]B[unk]] and 1[P[unk]H[unk]]. P is a bacteriochlorophyll dimer, B is a bacteriochlorophyll absorbing at 800 nm, and H is a bacteriopheophytin. In the presence of Q[unk], the energy of 1[P[unk]B[unk]] is about 0.025 eV above that of 1[P[unk]H[unk]], 1[P[unk]H[unk]] can decay to a triplet state, PR, which also is an equilibrium mixture of two states, separated by about 0.03 eV. The lower of these appears to be mainly a locally excited triplet state of P, 3P; the upper state contains a major contribution from a triplet charge-transfer state, 3[P[unk]B[unk]]. The temperature dependence of delayed fluorescence from PR indicates that 3P lies 0.40 eV below the excited singlet state, P*, which is about 0.05 eV above 1[P[unk]H[unk]]. The 1,3[P[unk]B[unk]] charge-transfer states thus appear to interact with the locally excited states of P and B to give singlet and triplet states that are separated in energy by about 0.35 eV. This is 106 times larger than the splitting between 1[P[unk]H[unk]] and 3[P[unk]H[unk]] and implies strong orbital overlap between P[unk] and B[unk]. This is consistent with recent picosecond studies which suggest that electron transfer from P* to B occurs within 1 ps and is followed in 4 to 10 ps by electron transfer from B[unk] to H.

Keywords: photosynthesis, electron transfer, spin exchange interactions

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Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Blankenship R. E., Parson W. W. The involvement of iron and ubiquinone in electron transfer reactions mediated by reaction centers from photosynthetic bacteria. Biochim Biophys Acta. 1979 Mar 15;545(3):429–444. doi: 10.1016/0005-2728(79)90152-x. [DOI] [PubMed] [Google Scholar]
  2. Blankenship R. E., Schaafsma T. J., Parson W. W. Magnetic field effects on radical pair intermediates in bacterial photosynthesis. Biochim Biophys Acta. 1977 Aug 10;461(2):297–305. doi: 10.1016/0005-2728(77)90179-7. [DOI] [PubMed] [Google Scholar]
  3. Connolly J. S., Gorman D. S., Seely G. R. Laser flash photolysis studies of chlorin and porphyrin systems. I. Energetics of the triplet state of bacteriochlorophyll. Ann N Y Acad Sci. 1973;206:649–669. doi: 10.1111/j.1749-6632.1973.tb43243.x. [DOI] [PubMed] [Google Scholar]
  4. Dutton P. L., Kaufmann K. J., Chance B., Rentzepis P. M. Picosecond kinetics of the 1250 nm band of the Rps. sphaeroides reaction center: the nature of the primary photochemical intermediary state. FEBS Lett. 1975 Dec 15;60(2):275–280. doi: 10.1016/0014-5793(75)80730-7. [DOI] [PubMed] [Google Scholar]
  5. Dutton P. L., Prince R. C., Tiede D. M., Petty K. M., Kaufmann K. J., Netzel T. L., Rentzepis P. M. Electron transfer in the photosynthetic reaction center. Brookhaven Symp Biol. 1976 Jun 7;(28):213–237. [PubMed] [Google Scholar]
  6. Fajer J., Borg D. C., Forman A., Dolphin D., Felton R. H. Anion radical of bacteriochlorophyll. J Am Chem Soc. 1973 Apr 18;95(8):2739–2741. doi: 10.1021/ja00789a085. [DOI] [PubMed] [Google Scholar]
  7. Fajer J., Brune D. C., Davis M. S., Forman A., Spaulding L. D. Primary charge separation in bacterial photosynthesis: oxidized chlorophylls and reduced pheophytin. Proc Natl Acad Sci U S A. 1975 Dec;72(12):4956–4960. doi: 10.1073/pnas.72.12.4956. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Feher G., Okamura M. Y., McElroy J. D. Identification of an electron acceptor in reaction centers of Rhodopseudomonas spheroides by EPR spectroscopy. Biochim Biophys Acta. 1972 Apr 20;267(1):222–226. doi: 10.1016/0005-2728(72)90155-7. [DOI] [PubMed] [Google Scholar]
  9. Godik V. I., Borisov A. Y. Short-lived delayed luminescence of photosynthetic organisms. I. Nanosecond afterglows in purple bacteria at low redox potentials. Biochim Biophys Acta. 1979 Nov 8;548(2):296–308. doi: 10.1016/0005-2728(79)90137-3. [DOI] [PubMed] [Google Scholar]
  10. Haberkorn R., Michel-Beyerle M. E., Marcus R. A. On spin-exchange and electron-transfer rates in bacterial photosynthesis. Proc Natl Acad Sci U S A. 1979 Sep;76(9):4185–4188. doi: 10.1073/pnas.76.9.4185. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Haberkorn R., Michel-Beyerle M. E. On the mechanism of magnetic field effects in bacterial photosynthesis. Biophys J. 1979 Jun;26(3):489–498. doi: 10.1016/S0006-3495(79)85266-2. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Hoff A. J., Rademaker H., van Grondelle R., Duysens L. N. On the magnetic field dependence of the yield of the triplet state in reaction centers of photosynthetic bacteria. Biochim Biophys Acta. 1977 Jun 9;460(3):547–554. doi: 10.1016/0005-2728(77)90094-9. [DOI] [PubMed] [Google Scholar]
  13. Holten D., Hoganson C., Windsor M. W., Schenck G. C., Parson W. W., Migus A., Fork R. L., Shank C. V. Subpicosecond and picosecond studies of electron transfer intermediates in Rhodopseudomonas sphaeroides reaction centers. Biochim Biophys Acta. 1980 Oct 3;592(3):461–477. doi: 10.1016/0005-2728(80)90092-4. [DOI] [PubMed] [Google Scholar]
  14. Holten D., Windsor M. W., Parson W. W., Thornber J. P. Primary photochemical processes in isolated reaction centers of Rhodopseudomonas viridis. Biochim Biophys Acta. 1978 Jan 11;501(1):112–126. doi: 10.1016/0005-2728(78)90100-7. [DOI] [PubMed] [Google Scholar]
  15. Kaufmann K. J., Dutton P. L., Netzel T. L., Leigh J. S., Rentzepis P. M. Picosecond kinetics of events leading to reaction center bacteriochlorophyll oxidation. Science. 1975 Jun 27;188(4195):1301–1304. doi: 10.1126/science.188.4195.1301. [DOI] [PubMed] [Google Scholar]
  16. Okamura M. Y., Isaacson R. A., Feher G. Spectroscopic and kinetic properties of the transient intermediate acceptor in reaction centers of Rhodopseudomonas sphaeroides. Biochim Biophys Acta. 1979 Jun 5;546(3):394–417. doi: 10.1016/0005-2728(79)90076-8. [DOI] [PubMed] [Google Scholar]
  17. Parson W. W., Clayton R. K., Cogdell R. J. Excited states of photosynthetic reaction centers at low recox potentials. Biochim Biophys Acta. 1975 May 15;387(2):265–278. doi: 10.1016/0005-2728(75)90109-7. [DOI] [PubMed] [Google Scholar]
  18. Rafferty C. N., Clayton R. K. Properties of reaction centers of Rhodopseudomonas sphaeroides in dried gelatin films. Linear dichroism and low temperature spectra. Biochim Biophys Acta. 1978 Apr 11;502(1):51–60. doi: 10.1016/0005-2728(78)90131-7. [DOI] [PubMed] [Google Scholar]
  19. Rockley M. G., Windsor M. W., Cogdell R. J., Parson W. W. Picosecond detection of an intermediate in the photochemical reaction of bacterial photosynthesis. Proc Natl Acad Sci U S A. 1975 Jun;72(6):2251–2255. doi: 10.1073/pnas.72.6.2251. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Shuvalov V. A., Asadov A. A. Arrangement and interaction of pigment molecules in reaction centers of Rhodopseudomonas viridis. Photodichroism and circular dichroism of reaction centers at 100 k. Biochim Biophys Acta. 1979 Feb 8;545(2):296–308. doi: 10.1016/0005-2728(79)90207-x. [DOI] [PubMed] [Google Scholar]
  21. Shuvalov V. A., Asadov A. A., Krakhmaleva I. N. Linear dichroism of light-induced absorbance changes of reaction centers of Rhodospirillum rubrum. FEBS Lett. 1977 Apr 15;76(2):240–245. doi: 10.1016/0014-5793(77)80160-9. [DOI] [PubMed] [Google Scholar]
  22. Shuvalov V. A., Klevanik A. V., Sharkov AV J. u., Matveetz A., Krukov P. G. Picosecond detection of BChl-800 as an intermediate electron carrier between selectively-excited p870 and bacteriopheophytin in Rhodospirillum rubrum relaction centers. FEBS Lett. 1978 Jul 1;91(1):135–139. doi: 10.1016/0014-5793(78)80034-9. [DOI] [PubMed] [Google Scholar]
  23. Shuvalov V. A., Klimov V. V. The primary photoreactions in the complex cytochrome-P-890-P-760 (bacteriopheophytin760) of Chromatium minutissimum at low redox potentials. Biochim Biophys Acta. 1976 Sep 13;440(3):587–599. doi: 10.1016/0005-2728(76)90044-x. [DOI] [PubMed] [Google Scholar]
  24. Straley S. C., Parson W. W., Mauzerall D. C., Clayton R. K. Pigment content and molar extinction coefficients of photochemical reaction centers from Rhodopseudomonas spheroides. Biochim Biophys Acta. 1973 Jun 28;305(3):597–609. doi: 10.1016/0005-2728(73)90079-0. [DOI] [PubMed] [Google Scholar]
  25. Vermeglio A., Breton J., Paillotin G., Cogdell R. Orientation of chromophores in reaction centers of Rhodopseudomonas sphaeroides: a photoselection study. Biochim Biophys Acta. 1978 Mar 13;501(3):514–530. doi: 10.1016/0005-2728(78)90118-4. [DOI] [PubMed] [Google Scholar]
  26. Vermeglio A., Clayton R. K. Orientation of chromophores in reaction centers of Rhodopseudomonas sphaeroides. Evidence for two absorption bands of the dimeric primary electron donor. Biochim Biophys Acta. 1976 Dec 6;449(3):500–515. doi: 10.1016/0005-2728(76)90159-6. [DOI] [PubMed] [Google Scholar]
  27. Werner H. J., Schulten K., Weller A. Electron transfer and spin exchange contributing to the magnetic field dependence of the primary photochemical reaction of bacterial photosynthesis. Biochim Biophys Acta. 1978 May 10;502(2):255–268. doi: 10.1016/0005-2728(78)90047-6. [DOI] [PubMed] [Google Scholar]
  28. van Grondelle R., Holmes N. G., Rademaker H., Duysens L. N. Bacteriochlorophyll fluorescence of purple bacteria at low redox potentials. The relationship between reaction center triplet yield and the emission yield. Biochim Biophys Acta. 1978 Jul 6;503(1):10–25. doi: 10.1016/0005-2728(78)90158-5. [DOI] [PubMed] [Google Scholar]

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