Sunday, May 20, 2012

Outperforming natural photosynthesis


“Researchers figure out how to outperform nature's photosynthesis”

“The Proceedings of the National Academy of Sciences (PNAS) last week published a paper titled "Solar hydrogen-producing bionanodevice outperforms natural photosynthesis."

“The authors are Carolyn E. Lubner, Amanda M. Applegate, Philipp Knörzerb, Alexander Ganagoc, Donald A. Bryantc, Thomas Happe and John H. Golbeck.”

“They modified the photosynthetic proteins found in cyanobacteria -- bacteria which gain their energy through photosynthesis.”

Ref: Solar hydrogen-producing bionanodevice outperforms natural photosynthesis PNAS 2011 108 (52) 20988-20991; published ahead of print December 12, 2011, doi:10.1073/pnas.1114660108


Although a number of solar biohydrogen systems employing photosystem I (PSI) have been developed, few attain the electron transfer throughput of oxygenic photosynthesis. We have optimized a biological/organic nanoconstruct that directly tethers FB, the terminal [4Fe-4S] cluster of PSI from Synechococcus sp. PCC 7002, to the distal [4Fe-4S] cluster of the [FeFe]-hydrogenase (H2ase) from Clostridium acetobutylicum. On illumination, the PSI–[FeFe]-H2ase nanoconstruct evolves H2 at a rate of 2,200 ± 460 μmol mg chlorophyll-1 h-1, which is equivalent to 105 ± 22 e-PSI-1 s-1. Cyanobacteria evolve O2 at a rate of approximately 400 μmol mg chlorophyll-1 h-1, which is equivalent to 47 e-PSI-1 s-1, given a PSI to photosystem II ratio of 1.8. The greater than twofold electron throughput by this hybrid biological/organic nanoconstruct over in vivo oxygenic photosynthesis validates the concept of tethering proteins through their redox cofactors to overcome diffusion-based rate limitations on electron transfer.

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