This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Kriegl, J. M. Articles by Nienhaus, G. U. Search for Related Content PubMed PubMed Citation Articles by Kriegl, J. M. Articles by Nienhaus, G. U.

Charge Recombination and Protein Dynamics in Bacterial Photosynthetic Reaction Centers Entrapped in a Sol-Gel Matrix

Jan M. Kriegl ^*, Florian K. Forster ^* and G. Ulrich Nienhaus ^* 

^* Department of Biophysics, University of Ulm, Ulm, Germany; and Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois

Correspondence: Address reprint requests to Gerd Ulrich Nienhaus, Dept. of Biophysics, University of Ulm, 89069 Ulm, Germany. Tel.: 49-731-502-3050; Fax: 49-731-502-3059; E-mail: uli{at}uiuc.edu.

Many proteins can be immobilized in silica hydrogel matrices without compromising their function, making this a suitable technique for biosensor applications. Immobilization will in general affect protein structure and dynamics. To study these effects, we have measured the P⁺Q_A^- charge recombination kinetics after laser excitation of Q_B-depleted wild-type photosynthetic reaction centers from Rhodobacter sphaeroides in a tetramethoxysilane (TMOS) sol-gel matrix and, for comparison, also in cryosolvent. The nonexponential electron transfer kinetics observed between 10 and 300 K were analyzed quantitatively using the spin boson model for the intrinsic temperature dependence of the electron transfer and an adiabatic change of the energy gap and electronic coupling caused by protein motions in response to the altered charge distributions. The analysis reveals similarities and differences in the TMOS-matrix and bulk-solvent samples. In both preparations, electron transfer is coupled to the same spectrum of low frequency phonons. As in bulk solvent, charge-solvating protein motions are present in the TMOS matrix. Large-scale conformational changes are arrested in the hydrogel, as evident from the nonexponential kinetics even at room temperature. The altered dynamics is likely responsible for the observed changes in the electronic coupling matrix element.

This article has been cited by other articles:

				R. Borrelli, M. Di Donato, and A. Peluso Role of Intramolecular Vibrations in Long-Range Electron Transfer between Pheophytin and Ubiquinone in Bacterial Photosynthetic Reaction Centers Biophys. J., August 1, 2005; 89(2): 830 - 841. [Abstract] [Full Text] [PDF]

				P. W. Fenimore, H. Frauenfelder, B. H. McMahon, and R. D. Young Bulk-solvent and hydration-shell fluctuations, similar to {alpha}- and {beta}-fluctuations in glasses, control protein motions and functions PNAS, October 5, 2004; 101(40): 14408 - 14413. [Abstract] [Full Text] [PDF]

				J. M. Kriegl and G. U. Nienhaus Structural, dynamic, and energetic aspects of long-range electron transfer in photosynthetic reaction centers PNAS, January 6, 2004; 101(1): 123 - 128. [Abstract] [Full Text] [PDF]