Reaction center triplet states in photosystem I and photosystem II. Academic Article uri icon

abstract

  • A photosystem I (PS I) particle has been prepared by lithium dodecyl sulfate digestion which lacks the acceptor X, and iron-sulfur centers B and A. Illumination of these particles at liquid helium temperature results in the appearance of a light-induced spin-polarized triplet signal observed by EPR. This signal is attributed to the triplet state of P-700, the primary donor, formed by recombination of the light induced radical pair P-700+ A1- (where A1 is the intermediate acceptor). Formation of the triplet does not occur if P-700 is oxidized or if A1 is reduced, prior to the illumination. A comparison of the P-700 triplet with that of P-680, the primary donor of Photosystem II, shows several differences. (1) The P-680 triplet is 1.5 mT (15 G) wider than the P-700 triplet. This is reflected by the zero-field splitting parameters, which indicate that P-700 is a slightly larger species than P-680. The zero-field splitting parameters do not indicate that either P-700 or P-680 are dimeric. (2) The P-700 triplet is induced by red and far-red light, while the P-680 triplet is induced only by red light. (3) The temperature dependences of the P-700 triplet and the P-680 triplet are different.

published proceedings

  • Biochim Biophys Acta

author list (cited authors)

  • Rutherford, A. W., & Mullet, J. E.

citation count

  • 95

complete list of authors

  • Rutherford, AW||Mullet, JE

publication date

  • April 1981