Leaves hold key to solar energy

Glasgow University scientists have made a dramatic breakthrough in the understanding of photosynthesis which could open up the way for new ways of harnessing solar power.

Neil Isaacs of Glasgow's chemistry department and Richard Cogdell of the division of biochemistry and molecular biology have been heading research for the past five years on obtaining the three dimensional structure of the complex of molecules which certain bacteria use to capture light for photosynthesis.

Photosynthesis is the means by which plants and some bacteria convert light into energy, and is the fundamental source of energy for life on Earth.

In a paper just published in the journal Nature, the pair describe the structure of the complex of proteins, chlorophyll and carotenoid molecules which capture light in photosynthetic bacteria.

Photosynthetic processes all take place using molecules embedded in the membranes, the outer walls, of cells. In photo-synthesis, light is captured by an assembly of molecules known as the light-harvesting complex.

The energy from this light is stored before being transmitted to another assembly called the reaction centre where the energy is converted to electrical energy inside the cell. The structure determined in Glasgow shows how the energy from light is captured, stored and transmitted to the reaction centre.

This is only the third membrane protein to have its structure determined, the first being the reaction centre. The team of German scientists who determined its structure a decade ago won the Nobel prize in 1988 for their work.

Now that the Glasgow team has revealed the structure of the light-harvesting complex, it is possible to see how light is captured and converted into electrical energy for the cell.

In a highly efficient process, the structure of the molecules enables light to be stored for short spells of time, measured in millionths of millionths of a second, but long enough for the organism to make use of it by converting it into electrical energy.

This blueprint from nature gives a design for manufacturing a new generation of solar power equipment which will operate under very low levels of light.

Professor Cogdell said that as well as opening up work in biophysics on understanding how the protein worked, Glasgow's findings would encourage biological research, in areas such as how hormones react with cells through membrane proteins.

There was a psychological barrier to break through before such research was begun, he said, since it could take between five and eight years to complete.

The Glasgow research had taken more than 11 years altogether. The funding had come predominantly through a rolling programme from the membranes initiative of the Biotechnology and Biological Sciences Research Council. But the funds threatened to run out had the breakthrough not come within the past 18 months.

"Funding bodies need to fight to maintain some long-termism and take a risk with some people," urged Professor Cogdell.