Bailey Damian Miles
Neurovascular Research Laboratory, Alfred Russel Wallace Building, Faculty of Life Sciences and Education, University of South Wales, Pontypridd, CF37 4AT UK.
Bioelectron Med. 2018 Oct 17;4:13. doi: 10.1186/s42234-018-0014-7. eCollection 2018.
Rising atmospheric oxygen (O) levels provided a selective pressure for the evolution of O-dependent micro-organisms that began with the autotrophic eukaryotes. Since these primordial times, the respiring mammalian cell has become entirely dependent on the constancy of electron flow with molecular O serving as the terminal electron acceptor in mitochondrial oxidative phosphorylation. Indeed, the ability to "sense" O and maintain homeostasis is considered one of the most important roles of the central nervous system (CNS) and likely represented a major driving force in the evolution of the human brain. Today, modern humans have evolved with an oversized brain committed to a continually active state and as a consequence, paradoxically vulnerable to failure if the O supply is interrupted. However, our pre-occupation with O, the elixir of life, obscures the fact that it is a gas with a Janus Face, capable of sustaining life in physiologically controlled amounts yet paradoxically deadly to the CNS when in excess. A closer look at its quantum structure reveals precisely why; the triplet ground state diatomic O molecule is paramagnetic and exists in air as a free radical, constrained from reacting aggressively with the brain's organic molecules due to its "spin restriction", a thermodynamic quirk of evolutionary fate. By further exploring O's free radical "quantum quirkiness" including emergent quantum physiological phenomena, our understanding of precisely how the human brain senses O deprivation (hypoxia) and the elaborate redox-signaling defense mechanisms that defend O homeostasis has the potential to offer unique insights into the pathophysiology and treatment of human brain disease.
不断上升的大气氧气（O）水平为依赖氧气的微生物进化提供了选择压力，这种进化始于自养真核生物。自这些原始时期以来，进行呼吸作用的哺乳动物细胞已完全依赖电子流的稳定性，分子氧作为线粒体氧化磷酸化中的终端电子受体。事实上，“感知”氧气并维持体内平衡的能力被认为是中枢神经系统（CNS）最重要的作用之一，并且可能是人类大脑进化的主要驱动力。如今，现代人类进化出了一个过度发达且持续活跃的大脑，因此，如果氧气供应中断，反而容易出现功能故障。然而，我们对氧气这种生命灵丹妙药的过度关注掩盖了一个事实，即它是一种具有两面性的气体，在生理控制的量下能够维持生命，但过量时却对中枢神经系统具有致命性。仔细观察其量子结构就能确切地明白原因；三重态基态双原子氧分子是顺磁性的，在空气中以自由基形式存在，由于其“自旋限制”，即进化命运的一种热力学特性，使其无法与大脑的有机分子发生剧烈反应。通过进一步探索氧气的自由基“量子特性”，包括新出现的量子生理现象，我们对人类大脑如何精确感知氧气剥夺（缺氧）以及维持氧气稳态的复杂氧化还原信号防御机制的理解，有可能为人类脑部疾病的病理生理学和治疗提供独特的见解。
