Nanoscale Photosynthesis: Photocatalytic Production of Hydrogen by Platinized Photosystem I Reaction Centers¶

Abstract

A study of the photocatalytic production of molecular hydrogen from platinized photosystem I (PSI) reaction centers is reported. At pH 7 and room temperature metallic platinum was photoprecipitated at the reducing end of PSI according to the reaction, [PtCl6]2- + 4e- + hv-->Pt decreases + 6Cl-, where it interacted with photogenerated PSI electrons and catalyzed the evolution of molecular hydrogen. The reaction mixture included purified spinach PSI reaction centers, sodium ascorbate and spinach plastocyanin. Experimental data on real-time catalytic platinum formation as measured by the onset and rates of hydrogen photoevolution as a function of time are presented. The key objective of the experiments was demonstration of functional nanoscale surface metalization at the reducing end of isolated PSI by substituting negatively charged [PtCl6]2- for negatively charged ferredoxin, the naturally occurring water-soluble electron carrier in photosynthesis. The data are interpreted in terms of electrostatic interactions between [PtCl6]2- and the positively charged surface of psaD, the ferredoxin docking site situated at the stromal interface of the photosynthetic membrane and which is presumably retained in our PSI preparation. A discussion of the rates of hydrogen evolution in terms of the structural components of the various PSI preparations as well as of those of the intact thylakoid membranes is presented.

Integrated photosystem II-based photo-bioelectrochemical cells

“…Different bioelectrochemical devices that implement the RC, PSI and/or PSII as light harnessing components for the activation of PBFCs producing photocurrents [19][20][21][22] , or fuel products [23][24][25] have been proposed. These PBFCs require the immobilization and electrical contacting of the light harnessing components with the electrode supports to the extent that photo-induced electrontransfer processes occur between the photosynthetic RC, thus enabling the generation of photocurrents (or their use for the synthesis of fuel products).…”

Novel Hydrogen Bioreactor and Detection Apparatus

“…2a. Our apparatus mimics a similar system at Oak Ridge National Laboratory, which has been described previously in a number of biohydrogen experiments [13,14,16,[19][20][21], with Table 1. The custom bioreactor designed for this system is shown in Fig.…”

Application of photosynthesis to artificial sight

“…6 is a schematic illustration of a platinized PSI reaction center. We have shown that the coupled system of platinized PSI reaction centers, sodium ascorbate and plastocyanin is capable of sustained photoevolution of molecular hydrogen [2]. Since the midpoint redox potential of hydrogen evolution at pH 7 is more negative than -0.4 V, vs. the normal …”

“…The following results are reported: (1) measurement of open circuit electrostatic potentials from isolated PSI reaction centers [1]; (2) measurement of hydrogen photoevolution from platinized PSI reaction centers under closed circuit conditions using the rate of hydrogen evolution as a measure of current flow [2]; (3) measurement of functional PSI activity after they have been inserted into the liposomes. 6 is a schematic illustration of a platinized PSI reaction center.…”

“…This project investigates a new area of multidisciplinary biomedical engineering research that builds on recent advances in nanotechnology of photosynthesis [1,2] and pattern electrical stimulation of the human retina [3] (Fig. 1).…”