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

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

Research output: Contribution to journalArticle

4 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
JournalJournal of Physical Chemistry B
Volume101
Issue number13
Publication statusPublished - Mar 27 1997

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Photosystem II Protein Complex
polarization (charge separation)
Rate constants
Accessories
Chlorophyll
accessories
Energy transfer
Anions
chlorophylls
Negative ions
Wavelength
energy transfer
Kinetics
anions
kinetics
wavelengths
excitation

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

Cite this

Direct measurement of the effective rate constant for primary charge separation in isolated photosystem II reaction centers. / Greenfield, Scott R.; Seibert, Michael; Govindjee, ; Wasielewski, Michael R.

In: Journal of Physical Chemistry B, Vol. 101, No. 13, 27.03.1997.

Research output: Contribution to journalArticle

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