Molecular Wiring for Enhanced Photocatalytic Hydrogen Evolution

Barbara R. Evans¹, Hugh M. O’Neill², Stacy A. Hutchens³, Barry D. Bruce^2,4,5, and Elias Greenbaum*^,1,4,5

 ¹Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831
²Department of Biochemistry, Cellular & Molecular Biology, University of Tennessee,
Knoxville, TN, 37996

³Department of Biomedical Engineering, University of Tennessee, Knoxville, TN 37996
⁴Graduate School of Genome Science and Technology, University of Tennessee, Knoxville, TN
37996

⁵Center of Excellence in Environmental Biotechnology, University of Tennessee, Knoxville, TN
37996

*Correspondence and reprint requests: E. Greenbaum, greenbaum@ornl.gov; This work was sponsored by a contractor of the U.S. Government under contract DE-AC05-00OR22725.

A simple photocatalytic hydrogen-evolving system will be described based on intermolecular electron transfer using isolated Photosystem I (PSI) reaction centers as the photoactive element. The system is comprised of platinized PSI covalently-linked to plastocyanin. Water soluble sodium ascorbate is the electron donor. Plastocyanin was attached to PSI by formation of peptide bonds with the cross-linking reagent, 1-ethyl-3,3-dimethyl aminopropyl carbodiimide. Compared to the unlinked proteins, cross-linking of PC and PSI resulted in a substantial increase in light-driven reduction of hexachloroplatinate ions (PtCl6^2- + 4e^- o Pt^p + 6Cl^-). Hydrogen photoevolution by platinized cross-linked PC-PSIPt was increased three-fold both in initial rate and total yield. Analysis of the reaction indicates that covalent linkage of PC to PSI results in a greater rate of total electron throughput from sodium ascorbate to light-activated hydrogen evolution. In addition, although photocatalytic hydrogen-evolving activity was easily demonstrated in the cross-linked system, the native pathway of electron flow yielding enzymatic NADP+ reduction activity was not observed upon addition of the natural PSI electron-accepting system, ferredoxin+ ferredoxin:NADP⁺ oxidoreductase.

© 2002-2007

International Association for Nanotechnology. All rights reserved - All rights reserved - Privacy Policy
International Association of Nanotechnology, Inc.
2386 Fair Oaks Boulevard
Sacramento, CA 95825   
P.O. Box 231823
Sacramento, CA 95823 USA
Tel. 916-529-4119   Fax. 916-244-7029
  
Email: info@ianano.org