| Popis: |
The heliobacteria are distinguished from other groups of photosynthetic bacteria by their unusual pigmentation. The first species of this group, Heliobacterium chlorum, was discovered about 6 years ago by Gest and Favinger (1). The main pigment of H. chlorum and other heliobacteria is Bchl g (2). At low temperature, three different spectral forms can be discerned in the antenna: Bchl g 778, Bchl g 793 and Bchl g 808 (3). Photooxidation of the primary electron donor P798 causes a bleaching with a maximum near 798 nm at room temperature (4) and near 793 nm at 5 K (5). This communication presents an analysis of flash-induced absorbance changes at 15 K. Electron transport from P798 to the primary electron acceptor was observed at this temperature. The rate of electron transport to the secondary acceptor was found to be 2 – 3 times faster than at 300 K. Significant bleaching of antenna pigments was only observed above 800 nm, indicating that excitation energy is rapidly transferred to the long-wave pigment, Bchl g 808. |
