LOW TEMPERATURE ELECTRON TRANSFER IN A_0 BINDING SITE POINT MUTANTS STUDIED USING TRANSIENT EPR AND CW EPR

摘要

The electron transfer from A_1~- to F_X in Photosystem I (PS I) is biphasic at ambient temperature and at low temperature two fractions of reaction centres are found with cylic electron transfer to A_1 occuring in one stable charge separation to F_A/F_B occurs in the other, (see Leibl & Brettel 2001 for a review). At present it is not clear which factors in the reaction centre lead to the two phases at room temperature and two fractions at low temperature nor is it clear whether they are correlated.Usually, this behaviour is described in terms of the directionality of the electron transfer. Bidirectionality: The PS I reaction center contains two pseudosym-metric cofactor branches bound to PsaA and PsaB (Fromme et al 2001).