The use of protein crystallography led in 1995 to Richard Cogdell's (botany) and Neil Isaacs's (chemistry) research groups determining the three dimensional structure of a light-harvesting complex (LH2) from the purple bacterium Rhodopseudomonas acidophila.
The LH2 complex is a major component of the photosynthetic apparatus of those species of bacteria that use light as a source of energy. In these bacteria, bacteriochlorophyll pigments in the light-harvesting complexes absorb light. This energy is then funnelled to another large protein-pigment complex, called the reaction centre, where it is converted into a chemically useable form. This capture and transfer process operates with nearly 100% efficiency.
The structure of the light-harvesting complex revealed how the energy is captured and then transmitted on to a reaction centre. It showed how the protein scaffold holds the pigments in precise orientations that maximise the efficiency of energy transfer; how the assembly protects itself against damage by species of reactive oxygen formed by the incident light; and how some bacteria have adapted to grow under low-light conditions by mutating specific amino acids in the proteins.
This study has led to research into ways of using solar energy to produce fuels.