How hydrogenases work at the atomic level

可再生能源是利用阳光的同义词，但太阳并不总是发光的。在绿色植物中，来自阳光的能量通过将水和二氧化碳转化为糖和氧气来储存。科学家们对发现模仿绿叶中发生的过程的方法非常感兴趣，不是为了产生糖，而是通过分解丰富的水来产生氢（H2）。氢是所有分子中最小的，因此是未来最重要的主要燃料：除了利用阳光本身，氢可以从任何普通的电能来源（如风力发电场的剩余电力）产生。储存在氢气中的能量要么通过燃烧释放出来，要么在燃料电池中转化为电能，但氢气也是制造肥料和其他化学品（包括运输用液体燃料）的原材料。在学习如何以低成本最有效地利用和生产氢气的过程中，科学家们再次将目光投向了大自然本身。最近，在发现微生物如何有效地生产和利用氢作为代谢物方面取得了很大进展，并且现在已经知道了被称为氢化酶的酶催化这一反应的机制的许多细节。“激活”氢意味着在两个氢原子之间形成或断开化学键。在氢化酶的活性位点上，电子从其他原子处进入或离开氢分子，仅仅很小的距离就很关键。酶已经进化到每个活性位点的原子都在正确的位置。这项即将进行的研究将确定氢化酶活性位点上每个不同原子的位置和作用，为科学家们绘制未来氢催化剂的“蓝图”。为了在原子水平上确定这些信息，需要基因工程与使用x射线衍射以尽可能高的分辨率进行结构定义相结合。通过x射线检测氢原子的位置是不容易的，尤其是当它们在像酶这样的大分子中时，因此一个重要的挑战将是通过仔细注意样品的均匀性和结晶来实现极高的分辨率。人们还将努力测试通过制造一种基因工程变体来获得一种“被困在作用中的”氢化酶结构的可行性，这种变体中H2被束缚但不能进一步反应。这项研究的最终目标是看看这种“被困在活动中的”氢化酶的结构是否可以用中子衍射来确定，因为中子能够精确定位氢原子的精确位置，从而有可能观察到氢分子本身。

Renewable energy is synonymous with exploiting sunlight, but the sun does not always shine. In green plants, energy from sunlight is stored by using it to convert water and carbon dioxide into sugars and oxygen. Scientists are very interested in discovering ways of mimicking the processes occurring in the green leaf, not so much to produce sugars but to make hydrogen (H2) by splitting water an abundant resource. Hydrogen, the smallest of all molecules, is therefore the most important primary fuel of the future: aside from using sunlight itself, H2 can be produced from any common source of electrical energy (such as surplus electricity from windfarms). The energy stored in H2 is released either by combustion or by its conversion back into electricity in fuel cells, but H2 is also a raw material for making fertilisers and other chemicals including liquid fuels for transport. In learning how to use and produce H2 most efficiently, at low cost, scientists are looking again to nature itself. Much progress has recently been made in discovering how effective microorganisms are in producing and using hydrogen as a metabolite, and many details of the mechanism by which enzymes known as hydrogenases catalyse this reaction are now known. 'Activating' hydrogen means making or breaking the chemical bond between two hydrogen atoms. Electrons are moved into or from the hydrogen molecule from other atoms in the active site of hydrogenases, and just tiny distances are critical. The enzymes have evolved to have every atom of the active site in just the right place. The research to be carried out will identify the positions and roles of each of the different atoms of the active site of hydrogenases, leading scientists to a 'blueprint' by which to create the hydrogen catalysts of the future. To determine this information at the atomic level requires genetic engineering to be combined with structural definition at the highest resolution possible using x-ray diffraction. It is not easy to detect the positions of hydrogen atoms by x-rays and this is particularly the case when they are in giant molecules like enzymes: therefore an important challenge will be to achieve extremely high resolution by careful attention to sample homogeneity and crystallisation. Efforts will also be made to test the feasibility of obtaining a structure of a hydrogenase 'trapped in action' by making a genetically-engineered variant in which H2 is bound but cannot react further. The ultimate goal of the research would be to see if the structure of such a 'trapped in action' hydrogenase can be determined using neutron diffraction, as neutrons are able to pinpoint the accurate position of hydrogen atoms, making it possible to observe the hydrogen molecule itself.