Directionality of Electron Transfer in Photosystem 1

Photosystem 1 (PS1) is one of the multi‐subunit, pigmented protein complexes which drive the initial processes of light utilization in oxygenic photosynthesis. The PS1 complex has approximately 100 packed chlorophyll (Chls) molecules that form the antenna and isolated functional redox cofactors make the reaction center (RC). These cofactors are arranged in pseudo‐symmetric branches. The electron transfer (ET) along the two branches has been confirmed but charge separation (CS) and its kinetics need further study to completely understand the speedy flow of electrons in PS1. We have made PS1 mutants in the two branches by selecting two target sites near ec2 on both sides, these are:PsaA‐Asn601, PsaB‐Asn587 (coordinates H2O serving as axial ligand to ec2): converted to Cys, His, Ile, Asp, Asn PsaA‐Ala680, PsaB‐Ala660 (pointing at ec2): converted to His, Lys, Leu, Tyr. The aim of this work is to know what controls the relative usage of the two branches? where primary charge separation occurs? what role do the two Chls, ec2A and ec2B have in deciding which branch electrons use and why?