Future energy from photosynthetic protein

By JW Dowey - 29 Nov 2013 13:30:1 GMT
Future energy from photosynthetic protein

The photosynthetic megacomplex from a cyanobacterium, which scientists have managed to isolate in its complete, functioning form, weighs about 6 million Daltons. It has three parts: on top is a light-harvesting antenna complex called a phycobilisome that captures and funnels the energy in sunlight to two reaction centers, Photosystem II (the complex protruding beneath the antenna) and Photosystem I (the complexes to either side Photosystem II). The whole megacomplex is embedded in a membrane shown as a green carpet. Credit: © Haijun Liu

The energy of sunlight is our energy source for almost everything. As the energy reaches proteins in leaves, they can transform it and exchange the electrons until great power can be aplied for growth, reproduction and of course, passed on to the animal consumer. Science has found the simpler mechanisms of early photosynthesisers easier to investigate, so cyanobacteria are the source of this latest research.

The results of this organic photo-electric research are similar to our parallel photovoltaic technologies that are developing fast, but purely organic, just as the computer chips of the future are seemingly to be constructed of protein. All we need to do is nick the photosynthetic complex out of the cell and copy its functions. The light-harvesting antenna of the complex takes photons and sends them to reaction centers. Cytochromes and other substances are needed for electron transfers just as you have in respiration. Once that is achieved, the possibility is that light at many intensities can be harvested anywhere.

What comes next isn't obvious. We certainly need to study how the cyanobacteria and plants manage to adapt to different conditions, but the prize will be to understand how the energy can be transferred out and stolen by the energy hungry human race. This is a good alternative to the photoelectric cell, but perhaps we will continue with the "hard" photovoltaic technology, even though it seems already out-of-date compared with soft tissues doing our work for us.

Haijun Liu and six colleagues, all from Washington University in St Louis, present their paper in the journal "Science.".