Chirality-Induced Spin Selectivity in Biology:The Role of Spin-Polarized Electron Current in Biological Electron Transport & Redox Enzymatic Activity

量子力学是描述纳米尺度系统行为的基本理论。在过去的三十年里，我们在与基本生物功能相关的各种生物分子系统中看到了越来越多的量子力学效应的表现。在光合作用中，已经检测到捕光的光合作用复合体的长寿命振动相干。这种在室温下出人意料的长寿命量子相干赋予了天然光合作用复合体显着的能量转移效率。在鸟类导航中，隐色素蛋白内部的自由基对的光生成为一种磁感应机制。自由基对处于单态(不活跃)或三态(活跃)自旋态的时间受地面弱磁场方向的影响。这在许多鸟类和植物中被用作一种精确的指南针。上述自由基对机制也为解释活性氧物种(ROS)的产生和控制提供了科学基础，ROS在细胞信号和自我稳定中起着至关重要的作用。上述案例提供了新兴量子生物学领域的快速示例，该领域扩展到其他非常不同的领域，如嗅觉、认知、DNA氧化损伤等。在所有上述示例中，最引人注目的不仅仅是量子力学本身的表现，这一点出现在研究生物系统的分子水平上，而是自然界如何进化来控制这种分子尺度的过程来实现重要功能。理解自然界如何协调量子力学过程使其具有优势，这与当前的量子技术时代非常相关。上述例子告诉我们，电子自旋在生物过程中发挥着意想不到的重要作用。该项目建议研究一种基于电子自旋的新的量子生物效应，其影响扩展到所有手性氧化还原生物分子系统。其关键的潜在机制是基于手性诱导的自旋选择性(CISS)，它指的是手性分子结构固有的选择电子自旋的特定成分的能力，从而导致自旋极化。当电流流过手性分子系统时，瞬时电子经历的自旋极化程度类似于标准磁性设备在外加磁场下发生的情况。CISS效应提供了两个与生物学相关的基本成分：(1)它发生在室温下，(2)在没有外部磁场的情况下工作。我们的工作团队带来了一种独特的理论-实验方法，结合了先进的单肽/蛋白质电学表征和自旋极化电子传输理论的最新发展。利用这种协同作用的方法，该联盟已经在单个3纳米长的α-螺旋多肽序列中展示了极大的电子自旋极化(&gt；60%)，该序列被困在浸泡在生理介质中的受控纳米级间隙中。该项目建立在这些杰出结果的基础上，以(1)生成螺旋多肽中顺效应的原子图，(2)量化(1)通过氧化还原蛋白质的电荷传输的影响，以及(3)研究顺式效应对氧化还原酶反应的影响。我们预计，我们的结果将开辟量子生物学的一个新领域，为与疾病机制和生物能源相关的生物氧化还原化学带来基础知识。这种知识超越了生物领域，为量子信息中新材料和应用的设计带来了革命性的解决方案。

Quantum mechanics is the fundamental theory that describes the behaviour of nanoscale systems. In the past three decades, we have seen a growing number of manifestations of quantum mechanical effects in a variety of biomolecular systems connected to essential biological functions. In photosynthesis, long-lived vibrational coherences have been detected for light-harvesting photosynthetic complexes. Such unexpected long-living quantum coherence at room temperature confers remarkable energy transfer efficiencies to natural photosynthetic complexes. In avian navigation, photo-generation of a radical pair inside a cryptochrome protein is exploited as a mechanism of magnetoreception. The time the radical pair stays in a singlet (inactive) or a triplet (active) spin state is influenced by the direction of the weak terrestrial magnetic field. This is exploited as a precise compass in many bird species and plants. The above mentioned radical pair mechanism offers also scientific foundations to explain the production and control of Reactive Oxygen Species (ROS), with essential roles in cell signalling and homeostasis.The above cases provide a quick survey of examples in the emerging field of Quantum Biology, which extends to other very different areas such as olfaction, cognition, DNA oxidative damage, etc. The most striking point in all the above examples is not just the manifestation of quantum mechanics itself, which arises when studying the biological system down to the molecular level, but in how nature has evolved to control such molecular-scale processes to fulfil vital functions. Understanding how nature orchestrate quantum mechanical processes to its advantage is of much relevance to the current quantum technology era.The above examples have taught us about the unexpected important role of the electronic spin in biological processes. This project proposes to study a new quantum biological effect based on the electron spin whose impact extends to all chiral redox biomolecular systems. The key underlying mechanism is based on the Chirality-Induced Spin Selectivity (CISS), which refers the inherent ability of chiral molecular structures to select one particular component of electronic spin, thereby leading to spin polarization. When an electric current flows through a chiral molecular system, the transient electrons experience a degree of spin polarization similar to what occurs in a standard magnetic device under applied magnetic fields. The CISS effect presents two essential ingredients relevant to biology; (1) it occurs at room temperature and (2) operates in the absence of external magnetic fields. The translation of the CISS effect into biology means a chiral peptide scaffold surrounding a redox co-factor acts as a "smart matrix" which magnetically prepares the spin of the crossing electrons going into the redox centre.Our working team brings a unique theoretical-experimental approach combining advanced single-peptide/protein electrical characterization and the latest developments in the theory of spin-polarized electron transport. Using this synergistic approach, this consortium has already demonstrated exceedingly large electron spin polarization (>60%) in an individual 3 nanometres long alpha-helical peptide sequence trapped in a controlled nanoscale gap immersed in a physiological medium. This project builds upon these outstanding results to (1) generate an atomistic picture of the CISS effect in a helical peptide, (2) quantify the impact of (1) in the charge transport across a redox protein, and (3) study the CISS effect on a redox enzymatic reaction. We anticipate our results will open a new area in quantum biology bringing fundamental knowledge to biological redox chemistry relevant to disease mechanisms and bioenergy. This knowledge transcends the biological arena bringing revolutionary solutions to the design of new materials and applications in quantum information.