An alternative pathway of light-induced transmembrane electron transfer in photosynthetic reaction centers of Rhodobacter sphaeroides
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In the absorption spectrum of Rhodobacter sphaeroides reaction centers, a minor absorption band was found with a maximum at 1053 nm. The amplitude of this band is ~10,000 times less and its half-width is comparable to that of the long-wavelength absorption band of the primary electron donor P870. When the primary electron donor is excited by femtosecond light pulses at 870 nm, the absorption band at 1053 nm is increased manifold during the earliest stages of charge separation. The growth of this absorption band in difference absorption spectra precedes the appearance of stimulated emission at 935 nm and the appearance of the absorption band of anion-radical BA – at 1020 nm, reported earlier by several researchers. When reaction centers are illuminated with 1064 nm light, the absorption spectrum undergoes changes indicating reduction of the primary electron acceptor QA, with the primary electron donor P870 remaining neutral. These photoinduced absorption changes reflect the formation of the long-lived radical state PBAHAQA –.
Keywordsfemtosecond spectroscopy bacterial reaction centers electron transfer
- BA and BB
- HA and HB
bacteriopheophytins serving as electron acceptors
BChl special pair (PA and PB) that is a primary electron donor
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- 3.Shuvalov, V. A., Klevanik, A. V., Sharkov, A. V., Matveetz, Yu. A., and Krukov, P. G. (1978) Picosecond detection of BChl-800 as an intermediate electron carrier between selectively excited P870 and bacteriopheophytin in Rhodospirillum rubrum reaction centers, FEBS Lett., 91, 135–139.CrossRefPubMedGoogle Scholar
- 8.Kennis, J. T., Shkuropatov, A. Y., van Stokkum, I. H. M., Gast, P., Hoff, A. J., Shuvalov, V. A., and Aartsma, T. J. (1997) Formation of a long-lived P+BA – state in plant pheophytin-exchanged reaction centers of Rhodobacter sphaeroides R26 at low temperature, Biochemistry, 36, 16231–16238.CrossRefPubMedGoogle Scholar
- 9.Schmidt, S., Arlt, T., Hamm, P., Huber, H., Nagele, T., Wachtveitl, J., Zinth, W., Meyer, M., and Scheer, H. (1995) Primary electron-transfer dynamics in modified bacterial reaction centers containing pheophytin a instead of bacteriopheophytin a, Spectrochim. Acta, 51, 1565–1578.CrossRefGoogle Scholar
- 19.Khatypov, R. A., Khmelnitskiy, A. Y., Khristin, A. M., and Shuvalov, V. A. (2010) Femtosecond absorption band formation at 1080 and 1020 nm as an indication of chargeseparated states PA δ+PB δ– and P+BA – in photosynthetic reaction centers of the purple bacterium Rhodobacter sphaeroides, Dokl. Biochem. Biophys., 430, 24–28.CrossRefPubMedGoogle Scholar
- 24.Shuvalov, V. A., Shkuropatov, A. Ya., Kulakova, S. M., Ismailov, M. A., and Shkuropatova, V. A. (1986) Photoreactions of bacteriopheophytins and bacteriochlorophylls in reaction centers of Rhodopseudomonas sphaeroides and Chloroflexus aurantiacus, Biochim. Biophys. Acta, 849, 337–346.CrossRefGoogle Scholar