Electron Transfer to Light-Activated Photosynthetic Reaction Centers from Rhodobacter sphaeroides Reconstituted in a Biomimetic Membrane System

Abstract

Photosynthetic reaction centers (RCs) from Rb. sphaeroides with a genetically engineered 7-his-tag at the C-terminus of the M-subunit are bound to a Ni-NTA-modified gold surface. Subsequently, the bound RCs are subjected to in situ dialysis in the presence of lipid micelles to form a protein-tethered lipid bilayer membrane (ptBLM). Redox properties of the RC thus immobilized are investigated by cyclic voltammetry. Photocurrrents are generated in the range of 10 μA cm −2 , however, different from previous studies at potentials of −200 and −300 mV, and without cytochrome c as a mediator. The unexpected behavior is explained in terms of an interprotein reaction between RC molecules promoted by the lipid bilayer, which we had previously detected by surface-enhanced infrared absorption spectroscopy.

Biomimetic Photodiode Device With Large Photocurrent Response Using Photosynthetic Pigment-Protein Complexes

“…16 These results show superior performance compared to the previously reported work on similar systems where the waveform showed a nonsaturating profile with long rise and decay times in the order of minutes. [9][10][11] To evaluate the endurance of the photocurrent response, cycling stability test was performed by monitoring the photocurrent response as the device continuously cycled between dark and illuminated states. For cycling test, the light intensity was fixed at 320 mW/cm 2 .…”

“…9 An improvement in photocurrent density up to 10 µA/cm 2 was obtained when the protein was suspended into the supported lipid bilayer. 10 The highest photocurrent density response of 45 µA/cm 2 is obtained when the protein complex was densely packed via Langmuir film deposition. 11 Most of these works were conducted in bio-photo-electrochemical cells which required electrolyte solution and must be confined and sealed.…”

“…1 Most recently, the biomimetic strategy has been borrowed from photosynthetic organisms utilizing the whole photosynthetic pigments and proteins to be incorporated into the man-made photocurrent devices. [7][8][9][10][11][12][13] Thereby, the high efficiency of the photosynthesis might be retained in the artificial devices. Bilayer structure of recombinant ferredoxin and chlorophyll shows one directional transport of electron from chlorophyll to ferredoxin molecule during visible light exposure.…”

Kinetics of cytochrome c oxidase from R. sphaeroides initiated by direct electron transfer followed by tr-SEIRAS

“…Chemical reduction, particularly by CO, is known to elicit structural changes of the catalytic center of CcO, that might interfere with changes during enzymatic oxidation [25]. By contrast, in the case of EC excitation, the redox state of the CcO can be controlled simply by changing the electrode potential, even under aerobic conditions, as it was shown by CV, SEIRAS as well as SERRS [9][10][11]. The potential window, however, has to be extended in the negative direction down to -800 mV in order to cover not only the reduction of the catalytic center but also the reduction of protons transported to the inner side of the lipid bilayer (Schematic 1) [13,15].…”

“…Subsequently, the tethered protein was reconstituted into a lipid bilayer to form the protein-tethered bilayer lipid membrane (ptBLM) [6][7][8]. This system was later used to immobilize the photosynthetic reaction center as well as complex I of the respiratory chain [9][10][11].…”