The S(1) split signal of photosystem II; a tyrosine-manganese coupled interaction
Nicholas Cox1, Felix M Ho, Naray Pewnim
1Department of Chemistry, College of Science, Australian National University, Canberra, ACT 0200, Australia.
Abstract:
Detailed optical and EPR analyses of states induced in dark-adapted PS II membranes by cryogenic illumination permit characterization and quantification of all pigment derived donors and acceptors, as well as optically silent (in the visible, near infrared) species which are EPR active. Near complete turnover formation of Q(A)((-)) is seen in all centers, but with variable efficiency, depending on the donor species. In minimally detergent-exposed PS II membranes, negligible (<5%) oxidation of chlorophyll or carotenoid centers occurs for illumination temperatures 5-20 K. An optically silent electron donor to P680(+) is observed with the same decay kinetics as the S(1) split signal. Cryogenic donors to P680(+) seen are: (i) transient (t(1/2) approximately 150 s) tyrosine related species, including 'split signals' ( approximately 15% total centers), (ii) reduced cytochrome b(559) ( approximately 30-50% centers), and (iii) an organic donor, possibly an amino acid side chain, ( approximately 30% centers).
Related Concept Videos
Photosystem II
The pigment molecules are arranged across two photosystem domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
Photosystem I
Both these photosystems work in concert. An excited electron from PSII is relayed to PSI via an electron transport chain in the thylakoid membrane of the chloroplast, which is comprised of the carrier molecule plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As electrons move between PSII and PSI, they lose energy and must be re-energized...
Photosystems
Functioning of Photosystems
Photosystems contain many pigment molecules, such as chlorophylls and carotenoids, arranged in a particular organization across two domains — the antenna complex and the reaction center. The main aim of the pigment molecules...
The Photochemical Reaction Center
The Z-Scheme of Electron Transport in Photosynthesis
¹H NMR: Complex Splitting
Splitting diagrams or splitting tree diagrams are routinely used to depict such complex couplings. While drawing splitting diagrams, the splitting with the larger coupling constant is usually applied first.

