Mark Paddock, Ph.D University of California, San Diego

More recently, in collaboration with Professor Okamura (Physics) we have investigated the structural features of the bacterial reaction center that control the high quantum energy conversion and its directionality along the so called A-branch. A series of mutations were designed based on previous work in bacterial RCs to eliminate the primary quinone electron acceptor, reduce the quantum efficiency of electron transfer along the A-branch and enhance electron transfer along the B-branch. The result was a system in which only ~ 5% of the quinone was reduced in a single laser flash compared to nearly 100% in the native RC. But full Q_B reduction could be achieved upon continuous illumination. This system was subsequently used to investigate intermediate structural substates that are otherwise inaccessible or not measurable in the native RC. (More details are available in the publication list.)