Direct measurement of the effective rate constant for primary charge separation in isolated photosystem II reaction centers

Scott R. Greenfield, Michael Seibert, Michael R. Wasielewski

Research output: Contribution to journalArticle

56 Citations (Scopus)

Abstract

Transient absorption measurements of the pheophytin a anion band and Qx band bleach region using preferential excitation of P680 are performed on isolated photosystem II reaction centers to determine the effective rate constant for charge separation. A novel analysis of the Qx band bleach region explicitly takes the changing background into account in order to directly measure the rate of growth of the bleach. Both spectral regions reveal biphasic kinetics, with a ca. (8 ps)-1 rate constant for the faster component, and a ca. (50 ps)-1 rate constant for the slower component. We propose that the faster component corresponds to the effective rate constant for charge separation from within the equilibrated reaction center core and provides a lower limit for the intrinsic rate constant for charge separation. The slower component corresponds to charge separation that is limited by slow energy transfer from a long-wavelength accessory chlorophyll a.

Original languageEnglish
Pages (from-to)2251-2255
Number of pages5
JournalJournal of Physical Chemistry B
Volume101
Issue number13
DOIs
Publication statusPublished - Jan 1 1997

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry

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