PARENT SESSION
Posters P4Aa Chlorophyll and bilin based antenna systems. Abstracts (239-271)

Examination of excited-state dynamics in the Chld dominated cyanobacterium Acaryochloris marina by time- and space-correlated single photon counting spectroscopy. Hann-Jörg Eckert^*,1, Zdenek Petrasek², Joachim Huyer ², Christoph Theiss², Min Chen⁴, Anthony Larkum⁴, Hans Joachim Eichler², Klaus Kemnitz³, ¹ Max-Volmer-Laboratory, Berlin, Germany² Istitute of Optics, Berlin, Germany⁴ School of Biological Sciences, Sydney, New South Wales, Australia³ Europhoton GmbH, Berlin, Germany

ABSTRACT- The cyanobactrium Acaryochloris marina contains mainly Chl d as the major antenna pigment (1) and only small amounts of Chl a (less than 5%) and Phycobiliprotein (2). The Qy absorption band of Chl d is shifted to the red by more than 30 nm in comparison to Chl-a. In whole cells of A. marina the main red absorption band is observed at 714 nm and the steady state fluorescence exhibits a broad Chl d band at 724 nm (3). Chl-d was shown to be the primary donor of the reaction center of PS I in A. marina (4). The nature of the primary donor of PS II of A. marina is still a matter of discussion. In this report we study the excitation energy transfer within the antenna of A. marina by measuring the ps-fluorescence dynamics after excitation of whole cells with laser pulses of various wavelengths. We also present fluorescence lifetime images (FLI) of individual cells of A. marina. The FLI were obtained by time- and space-correlated single photon counting using a novel quadrant-anode (QA) MCP-PMT detector attached to a fluorescence microscope. References: 1)Miyashita, H., Ikemoto, H., Kurano, N., Adachi, K., Chihara, M. and Miyachi, S. (1996) Nature 383, 402. 2)Marquardt, J., Senger, H., Miyashita, H., Miyachi, S. and Moerschel, E. (1997) FEBS Lett 410, 428-432 3)Schiller, H., Senger, H., Miyashita, H., Miyachi, S. and Dau, H. (1997) FEBS Lett 410, 433-436. 4)Hu, Q., Miyashita, H, Iwasaki, I.,Kurano,N., Miyachi, S., Iwaki, M. and Itoh, S. (1998) Proc. Natl. Acad. Sci. USA 95, 13319-13323

KEY WORDS: fluorescence dynamics, Acaryochloris marina, fluorescence lifetime imaging microscopy (FLIM), phycobiliprotein