Abstract
We investigated the kinetics and function of the redox-components in reaction center of Hb. modesticuldum at cryogenic temperature by ESR spectroscopy. The core complexes of Hb. modesticuldum were illuminated at 230 K and cooled down to 14 K under illumination. We detected assymmetrical ESR signal with g = 2.0060 and 12 G line-width. This signal was assigned to the menasemiquinone radical analogous to A1- in PS I and proved that menasemiquinone exists in the core complexes. Under the same condition we also observed A/E/A/E (A: absorption E: emission) spin polarized signals by transient ESR at early times after flash. On the other hand, E/A/E pattern of polarized signals was observed in the dark frozen samples. We will discuss these results in comparison with PS I.
