ИСТИНА

Chlorosomes are the only natural light-harvesting complexes that are made from protein-free self-assembled pigment aggregates containing special (bacterio)-chlorophyll molecules as building blocks. They are the main antenna complexes of green bacteria which perform photosynthesis at extremely low light intensities. Thus these antenna complexes have highly unusual properties differing from other antenna complexes. Both the structure(s) as well as the optical spectra and the energy transfer dynamics in these antenna complexes are not well understood and are still a matter of intensive debate (1-7). We have performed various kinds of absorption spectroscopies (absorption, CD, anisotropic CD) on both wild type and mutant (QRU) chlorosomes of C. tepidum in order to better understand the molecular organizations of the pigment aggregates and their exciton properties in these chlorosomal aggregates. Based on the recently proposed syn-anti Bchl stacking structures for the bchQRU chlorosome mutant and the w.t. (2, 8), the linear optical properties of the tubular aggregates have been calculated using Redfield exciton theory. Comparison of the theoretical and experimental data (see example of calculated spectra for different size rods in Fig. 1) provides detailed insights into the exciton properties in these rod aggregates. Implications of these exciton structures for the energy transfer in these systems and their structure dependence on wild type and QRU structure will be discussed. References 1. A.R.Holzwarth, K.Griebenow, and K.Schaffner. J. Photochem. Photobiol. A 65, 61 (1992). 2. S.Ganapathy, G.Oostergetel, M.Reus, Y.Tsukatani, A.Gomez Maqueo Chew, F.Buda, D.A.Bryant, A.R.Holzwarth, and H.J.M.de Groot. Biochemistry 51, 4488 (2012). 3. Y.Tian, R.Camacho, D.Thomsson, M.Reus, A.R.Holzwarth, and I.G.Scheblykin. J. Am. Chem. Soc. 133, 17192 (2011). 4. A.Jesorka, A.R.Holzwarth, A.Eichhöfer, C.M.Reddy, D.Kinoshita, H.Tamiaki, M.Katterle, J.V.Naubron, and T.S.Balaban. Photochem. Photobiol. Sci. 11, 1069 (2012). 5. T.S.Balaban, H.Tamiaki, and A.R.Holzwarth. Chlorins programmed for self-assembly. In Supramolecular Dye Chemistry. Berlin. 2005. p. 1. 6. J.M.Linnanto and J.E.I.Korppi-Tommola. The Journal of Physical Chemistry B (2013). 7. J.Dostal, T.Mancal, R.Augulis, F.Vacha, J.Psencik, and D.Zigmantas. J. Am. Chem. Soc. 134, (2012). 8. S.Ganapathy, G.T.Oostergetel, P.K.Wawrzyniak, M.Reus, A.G.M.Chew, F.Buda, E.J.Boekema, D.A.Bryant, A.R.Holzwarth, and H.J.M.de Groot. Proc. Natl. Acad. Sci. USA 106, 8525 (2009).