Using ultrafast imaging of moving energy in photosynthesis, scientists at Imperial College London have determined the speed of crucial processes for the first time, which could be copied to produce fuels by artificial photosynthesis.
During photosynthesis, plants harvest light and, though a chemical process involving water and carbon dioxide, convert this into energy. A vital part of this process is using the light energy to split water into oxygen and hydrogen.
This is done by an enzyme called Photosystem II. Light energy is harvested by ‘antennae’, and transferred to the reaction centre of Photosystem II, which strips electrons from water. This conversion of excitation energy into chemical energy, known as ‘charge separation’, is the first step in splitting water.
It was previously thought that the process of charge separation in the reaction centre was the slowest step in photosynthesis that created a ‘bottleneck’, in comparison to the transfer of energy along the antennae.
However, since the structure of Photosystem II was first determined in 2001, there was some suggestion the energy transfer step was the slowest part of photosynthesis, but it was not yet possible to prove experimentally.
Using ultrafast imaging of electronic excitations that uses small crystals of Photosystem II, scientists from Imperial College London and Johannes Kepler University (JKU) in Austria have now been able to prove that the slowest step is in fact the process through which the plants harvest light and transfer its energy through the antennae to the reaction centre.
The new insights into the precise mechanics of photosynthesis should help researchers hoping to copy the efficiency of natural photosynthesis to produce green fuels. The study is published in Nature Communications.
Study author Dr Jasper van Thor, from the Department of Life Sciences at Imperial, said: “We can now see how nature has optimised the physics of converting light energy to fuel, and can probe this process using our new technique of ultrafast crystal measurements.
“For example, is it important that the bottleneck occurs at this stage, in order to preserve overall efficiency? Can we mimic it or tune it to make artificial photosynthesis more efficient? These questions, and many others, can now be explored.”
Although the researchers could determine which step is faster, both steps occur incredibly quickly – the whole process takes a matter of nanoseconds, with the individual steps of energy transfer and charge separation taking only picoseconds.
Read more at http://www.imeche.org/news/news-article/ultrafast-imaging-of-photosynthesis-could-help-development-of-green-fuel