Photoactivation: the assembly of the active site of the water oxidising enzyme

本项目旨在了解光系统2(PS2)的工作原理。这种酶存在于植物、藻类和一些微生物中。它是光合作用的主要太阳能转换器，光合作用是将太阳能转化为为生命提供动力的化学燃料的过程。地球上几乎所有的生命都依靠光合作用产生的能量生存。PS2不仅是一个重要的太阳能收集器，它也是唯一一种能够利用水制造燃料的酶。水(H2O)非常稳定；它需要大量的能量来分解它，一次两个分子，为燃料制造提供电子。PS2能够利用太阳能做到这一点。这个反应释放出质子(4H+)和氧气(O2)作为副产物。在没有O2的情况下，PS2在原始地球上的细菌中进化出来。这是生命进化过程中的一个关键事件。释放的氧气可以用于呼吸，这是一种比以前更有效的使用生物燃料的方式。能源利用效率的大幅提高意味着生物学可能会变得更加复杂：多细胞生命可能会发展。O2逃逸到大气中，并在紫外线辐射下转化为臭氧。然后形成的臭氧阻止了进一步致命的紫外线到达地球表面。总体而言，PS2提供了生命蓬勃发展的能量，让生命从石头下走出来，发展成我们所知的生命。正是这种酶改变了地球。这个项目的重点是PS2是如何工作的，以及与水反应的部分是如何内置到进行太阳能转换的部分中的。这种内在的过程被称为“光激活”，它发生在酶第一次制造和修复的时候。鉴于每一种植物和几乎每一种光合作用微生物都有数百万种这样的酶，而且每个PS2大约每30分钟需要修复一次，那么就有相当多的光活化正在进行。然而，人们对此知之甚少。众所周知，在光激活过程中，PS2对光损伤特别敏感。在压力条件下(太热、太冷、太干等)，这最终会杀死细胞，这可能会限制农作物的产量，并决定有机体的生存或死亡。我们希望了解这里发生了什么。这项工作可能对农民、农业科学产业、生态学家等有用，因为它应该允许开发提高作物产量和改善光合作用物种在不断变化的环境中生存的方法和过程。化石燃料是亿万年光合作用的产物，通过从古代大气中捕获二氧化碳，将太阳能转化为生物质。在地球时间尺度上，人类正处于将二氧化碳返还到大气中的过程中，这是“一眨眼的时间”，这正在改变地球。也许科学家目前面临的最大挑战是通过寻找化石燃料的替代品来解决能源/气候危机。越来越明显的是，太阳能是唯一足够大到可以做到这一点的替代能源。虽然将太阳能转换为电能很简单，但要解决我们的能源需求，特别是交通运输需求，我们需要燃料。太阳能燃料生产是一项至关重要的要求。自然光合作用是最大的太阳能燃料产生者，但它的速度缓慢且效率低下，我们不能依赖自然光合作用来取代需要亿万年才积累起来的化石燃料。人造太阳能燃料生产的目的是从自然光合作用中挑选出最好的特征，以制造出更高效的人工版本。水裂解酶是改变地球的酶，是这些研究的主要重点。目前的研究将提供关于这种酶如何工作、如何制造以及如何修复的关键信息：这些信息对于通过人工光合作用生产太阳能燃料至关重要。

This project is aimed at understanding how Photosystem 2 (PS2) works. This enzyme is found in plants, algae and some microbes. It is the main solar converter of photosynthesis, the process by which solar energy is converted to the chemical fuels used for powering life . Nearly all life on the planet runs on energy that came from photosynthesis. PS2 is important not just as a solar collector; it is the only enzyme that has is able to use water to make fuel. Water (H2O) is very stable; it takes a lot of energy to rip it apart, two molecules at a time, to provide electrons for fuel making. PS2 is able to do this using solar energy. This reaction releases protons (4H+) and oxygen gas (O2) as side-products.PS2 evolved in bacteria on the primitive Earth when O2 was absent. This was a key event in the evolution of life. The O2 released could be used for respiration, a much more efficient way of using biological fuels than existed previously. This drastic jump in the efficiency of energy use meant that biology could become much more complicated: multicellular life could develop. The O2 escaped to the atmosphere and was converted to ozone by UV radiation. The ozone formed then blocked further deadly UV from reaching the surface of the planet. Overall, PS2 provided the energy for life to flourish, allowed life to come out from under the stones and to develop into life as we know it. It is the enzyme that changed the planet.This project is focused on how PS2 works and how the part that reacts with water is built into the part that does the solar conversion. This building-in process is called "photoactivation" and it occurs when the enzyme is first made and when it is repaired. Given that every plant and nearly every photosynthetic microbe has many millions of these enzymes and that each PS2 needs to be repaired about every 30 minutes, then there is rather a lot of photoactivation going on. And yet very little is known about it. It is known that during photoactivation PS2 is particularly sensitive to being damaged by light. Under stress conditions (too hot, too cold, too dry, etc), this can end up killing the cell and this can limit the yields of crops and determine whether the organism lives or dies. We wish to understand what is going on here. The work is likely to be useful to farmers, the agri-science industry, ecologists etc because it should allow methods and processes to be developed for improving yields of crops and improving survival of photosynthetic species in a changing environment. The fossil fuels represent the product of eons of photosynthesis converting solar energy to biomass by the capture CO2 from the ancient atmosphere. Humans are in the process of returning the CO2 to the atmosphere in what is "the blink of an eye" on a planetary time-scale and this is changing the planet. Perhaps the biggest challenge to scientists at present is to solve the energy/climate crisis by finding alternatives to fossil fuels. It is becoming clear that solar energy is the only alternative energy source that is big enough to do this. While converting solar energy to electricity is straightforward, to solve our energy needs, particularly for transport, we require fuels. Solar fuel production is a crucial requirement. Natural photosynthesis is the biggest solar fuel producer however it does this slowly and inefficiently and we cannot rely on natural photosynthesis to replace fossil fuels that took eons to accumulate. Artificial solar fuel production aims to "cherry-pick" the best features from natural photosynthesis to make a more efficient artificial version. The water splitting enzyme, the enzyme that changed the planet, is the main focus of scrutiny for these studies. The current research will provide key information on how this enzyme works, how it is made and how it is repaired: information that is key for solar fuel production by artificial photosynthesis.