Terahertz electron paramagnetic resonance: A window on biological exploitation of quantum mechanics

每个读报纸或看电视新闻的人都会知道，我们正面临一场能源危机。世界上的化石燃料能源储量正在减少，但我们对能源的渴求却在以前所未有的速度加速。科学家和工程师梦想通过获取太阳的巨大能量来解决这个问题，通过分解水和形成氢气来储存能量。只要我们能找到一种高效而经济的方法来进行这种化学转化，这个梦想就可以成为现实。我们今天最大的希望在于利用自然界自身的生物催化剂--酶的力量来促进所需的化学反应。酶是非常有效的催化剂，使化学反应的速度比正常快数十亿倍。不幸的是，酶仅限于它们进化来催化的一系列特定的化学反应。到目前为止，根据我们的需求量身定做酶的尝试一直令人失望。考虑到我们对它们是如何工作的了解很少，这并不令人惊讶。传统的理论无法解释酶加速反应的惊人增长。一种新出现的酶催化理论表明，如果我们有一扇了解这个世界的窗口，我们会看到酶操纵一种被称为量子力学隧道效应的现象，使其成为自己的优势。我们设想化学反应克服减缓其进展的能量障碍，不是通过攀越它，而是通过直接穿过它。更奇怪的是，我们认为酶可能会利用其微妙的振动来挤压能量屏障，减小其厚度，以促进隧道效应并加快反应速度。这个项目试图确定酶是否真的进化到通过使用它们的运动来加速化学反应来操纵量子力学。为了做到这一点，将建造一种新的仪器，为这个世界提供一个独特的窗口。该仪器基于一种名为电子顺磁共振(EPR)的技术，是医院中更熟悉的磁共振成像(MRI)技术的近亲。虽然现有的仪器使用微波辐射，这限制了它们区分特征的能力，但这种新仪器将使用位于光谱的微波和红外部分之间的辐射，即所谓的太赫兹辐射。这将导致结构信息被精细地揭示出来。此外，太赫兹辐射的闪光将使用持续时间不到百万分之一秒的激光脉冲来产生，从而能够拍摄起作用的酶的快照。观察这些快速隧道过程的能力对于我们理解酶的功能是必不可少的，远远超出了现有仪器的能力范围。制作这些具有如此高清晰度结构信息的动作丰富的酶电影将依赖于多个太赫兹辐射爆发之间的精确计时。为了实现这些雄心勃勃的目标，该项目汇集了在激光开发、先进的EPR测量和仪器以及酶催化方面具有专业知识的工业和学术合作者。在我的领导下，这个项目将提供对成功开发这些非凡的生物催化剂至关重要的知识。

Everyone who reads a newspaper or watches the news on television will know that we are facing an energy crisis. The world's fossil-fuel energy reserves are dwindling and yet our thirst for energy is accelerating at an ever increasing rate. Scientists and engineers dream of solving this problem by harvesting the vast power of our Sun, storing its energy by breaking apart water and forming hydrogen gas. If only we could find an efficient and economical way of performing this chemical conversion the dream could become a reality. Our greatest hope today lies in harnessing the power of nature's own biological catalysts, enzymes, to promote desired chemical reactions. Enzymes are extremely efficient catalysts that allow chemical reactions to take place billions of times faster than normal. Unfortunately, enzymes are limited to the specific set of chemical reactions that they evolved to catalyse. Attempts to tailor enzymes to our needs have so far been disappointing. This is not surprising given our poor understanding of how they work. Conventional theory is unable to account for the incredible increases by which a reaction is speeded up by enzymes. A new emerging theory of enzyme catalysis suggests that if we had a window on this world we would see enzymes manipulating a phenomenon called quantum mechanical tunnelling to their advantage. We envisage chemical reactions overcoming the energy barrier that slows their progress, not by climbing over it, but by tunnelling directly through it. Even more strange, we think that enzymes might use their subtle vibrations to squeeze the energy barrier, reducing its thickness, to promote tunnelling and speed up the reaction. This project seeks to determine whether enzymes have indeed evolved to manipulate quantum mechanics, by using their movements to accelerate chemical reactions. In order to do this a novel instrument will be constructed to provide a unique window on this world. This instrument is based on a technique called Electron Paramagnetic Resonance (EPR), a cousin of the more familiar Magnetic Resonance Imaging (MRI) technology seen in hospitals. While existing instruments use microwave radiation, which limits their ability to distinguish features, this new instrument will use radiation that lies between the microwave and infra-red parts of the spectrum, so-called terahertz radiation. This will result in structural information being revealed in exquisite detail. In addition, flashes of terahertz radiation will be generated using pulses of laser light lasting less than one millionth of a millionth of a second enabling snap-shots to be taken of enzymes in action. The ability to watch these fast tunnelling processes is essential to our understanding of enzyme function and is far beyond the reach of existing instruments. Producing these action-packed enzyme movies with such high-definition structural information will rely on the precise timing between multiple bursts of terahertz radiation. To achieve these ambitious goals this project brings together a combination of industrial and academic collaborators with expertise in laser development, advanced EPR measurements and apparatus, and enzyme catalysis. Under my leadership, this project will provide knowledge crucially important to the successful exploitation of these remarkable biological catalysts.