Development of a microscopic gas diffusion-reaction model for a H2 producing biocatalyst

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Providing the technology for production of renewable energy is one of the grandchallenges of this century. There are alternatives to oil, gas and nuclear such as water, wind and solar power. Of those, the latter is a virtually unlimited power source and we think that every effort should be undertaken to try to harvest the power of the sun. This is not an easy task because light energy needs to be converted into a form of energy that can be stored and supplied on demand. A convenient storage medium are molecules comprised of atomsthat are held together by energy-rich covalent bonds. Indeed, over millions of years nature has stored sun light in form of organic molecules (fossil fuels) via natural photosynthesis. A carbon-free alternative storage medium is molecular hydrogen with the added advantage that the energy density that can be stored with hydrogen is significantly larger than for fossil fuels. Thus, molecular hydrogen is envisaged as one of the primary energy carriers of the future. One of the grand challenges for scientists is to find or design a cheap catalyst that allows for efficient production of hydrogen from sunlight and a source for hydrogen atoms, ideally water. Clearly, one of the most sustainable approaches to hydrogen production is photocatalytic water oxidation, although this process requires efficient catalysts. Their design is by no means trivial and can probably be considered as the holy grail of contemporary material science. A viable alternative that we investigate here is to exploit biological molecules (hydrogenases) that can be found in microbes such as green algae and cyanobacteria capable of photosynthetic water splitting. Pilot plants of H2 producing organisms exist, but there are major barriers that must be overcome to bring the process to commercial viability. The most important one that needs to be addressed is the high sensitivity of the organism's hydrogenase to molecular oxygen. Evolved under anaerobic conditions, the biomolecule gets inhibited or damaged upon exposure of the oxygen that is around us in the atmosphere. There is evidence that hydrogenases may be modified so as to render the molecule less sensitive to oxygen. In order to facilitate this optimization process we proposehere to investigate theoretically the primary events of the oxidative damage, that is diffusion and binding of oxygen molecules to the active site of hydrogenases, by developing novel molecular simulation methods. The simulations will help to understand and interpret recent experimental measurements on a molecular level. For example, they will allow us to understand which pathways oxygen molecules take before they damage the active site and how fast this process occurs. The microscopic information gained from simulation will be vital for the suggestion of modifications (mutations) of hydrogenase that aim to restrict the access and the binding of molecular oxygen while leaving the catalytic power for hydrogen production unchanged. The effects of the suggested mutations will be predicted by our simulations and tested in vitro by an experimental colleague. The long term goal of this project is to obtain a hydrogenase mutant with significantly increased aerotolerance, which can be used for hydrogen production on a technological scale. This would have a tremendous socio-economic impact as the hydrogen industry is likely to take a prominent position on the future energy market.