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

为生产可再生能源提供技术是本世纪的重大挑战之一。除了石油、天然气和核能，还有水、风能和太阳能等替代能源。其中，后者实际上是一种无限的能量来源，我们认为应该尽一切努力获取太阳的能量。这并不是一项容易的任务，因为光能需要转化为一种可以按需储存和供应的能量。一种方便的存储介质是由原子组成的分子，这些原子通过能量丰富的共价键结合在一起。事实上，数百万年来，自然界通过自然光合作用以有机分子(化石燃料)的形式储存了太阳光。一种无碳的替代存储介质是分子氢，另外一个优点是，与氢一起存储的能量密度比化石燃料要大得多。因此，分子氢被认为是未来的主要能源载体之一。科学家面临的重大挑战之一是寻找或设计一种廉价的催化剂，使其能够从阳光中高效地生产氢气，并提供氢原子的来源，最好是水。显然，最可持续的制氢方法之一是光催化水氧化，尽管这一过程需要高效的催化剂。它们的设计绝不是微不足道的，很可能被视为当代材料科学的圣杯。我们在这里研究的一个可行的替代方案是利用生物分子(氢酶)，这种生物分子可以在绿藻和蓝藻等微生物中找到，能够进行光合作用分解水分。产氢微生物的中试工厂是存在的，但要将这一过程转化为商业可行性，必须克服一些重大障碍。需要解决的最重要的一个问题是生物体的氢酶对分子氧的高度敏感性。这种生物分子在厌氧条件下进化，暴露在大气中我们周围的氧气中会受到抑制或破坏。有证据表明，氢酶可以被修饰，从而降低分子对氧的敏感度。为了促进这一优化过程，我们建议通过发展新的分子模拟方法，从理论上研究氧化损伤的主要事件，即氧分子在氢酶活性部位的扩散和结合。这些模拟将有助于在分子水平上理解和解释最近的实验测量。例如，它们将让我们了解氧分子在破坏活性部位之前走的是什么途径，以及这个过程发生的速度有多快。从模拟中获得的微观信息对于氢酶的修饰(突变)的建议至关重要，该修饰(突变)的目的是限制分子氧的访问和结合，同时保持制氢的催化能力不变。建议的突变的影响将通过我们的模拟进行预测，并由一位实验同事在体外进行测试。该项目的长期目标是获得一种氢酶突变体，其耐氧性显著提高，可以用于技术规模的氢气生产。这将产生巨大的社会经济影响，因为氢气工业很可能在未来的能源市场上占据突出地位。

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.