Szent-Györgyi A
Ciba Found Symp. 1978(67):3-18. doi: 10.1002/9780470720493.ch2.
The surrounding world can be divided into two parts: alive and inanimate. What makes the difference is the subtle reactivity of living systems. The difference is so great that it is reasonable to suppose that what underlies life is a specific physical state, 'the living state'. Living systems are built mainly of nucleic acids and proteins. The former are the guardians of the basic blueprint while the business of life is carried on by proteins. Proteins thus have to share the subtle reactivity of living systems. A closed-shell protein molecule, however, has no electronic mobility, and has but a low chemical reactivity. Its orbitals are occupied by electron pairs which are held firmly. The situation can be changed by taking single electrons out of the system. This unpairs electrons, leaves half-occupied orbitals with positive electron holes, making the molecules into highly reactive paramagnetic free radicals. The reactivity of the system depends on the degree of its electronic desaturation. Electrons can be taken out of protein molecules by 'electron aceptors' in 'cahrge transfer'. When life began, our globe was covered by dense water vapour. There was no light and no free oxygen. Electron acceptors could be made out of trioses by concentrating their carbon atoms as carbonyls at one end of the molecule. The resulting methylglyoxal is a weak acceptor which made a low level of development possible. When light appeared, free oxygen was generated by the energy of photons. Oxygen is a strong electron acceptor. Its appearance opened the way to the present level of development. The transfer of electrons from protein to oxygen is effected by a complex chemical mechanism which involves ascorbic acid.
有生命的和无生命的。造成这种差异的是生命系统微妙的反应活性。这种差异非常巨大，以至于有理由推测生命的基础是一种特定的物理状态，即“生命状态”。生命系统主要由核酸和蛋白质构成。前者是基本蓝图的守护者，而生命活动则由蛋白质进行。因此，蛋白质必须具备生命系统的微妙反应活性。然而，一个闭壳层的蛋白质分子没有电子流动性，化学反应活性也很低。其轨道被紧紧束缚的电子对占据。通过从系统中取出单个电子可以改变这种情况。这会使电子不成对，留下带有正电子空穴的半充满轨道，从而使分子变成高反应活性的顺磁性自由基。系统的反应活性取决于其电子不饱和程度。在“电荷转移”过程中，电子可以被“电子受体”从蛋白质分子中取出。生命起源时，我们的地球被浓密的水蒸气覆盖。没有光，也没有游离氧。通过将三碳糖分子一端的碳原子浓缩为羰基，可以形成电子受体。由此产生的甲基乙二醛是一种弱受体，它使得较低水平的发展成为可能。当光出现时，光子能量产生了游离氧。氧是一种强电子受体。它的出现为当前的发展水平开辟了道路。从蛋白质到氧的电子转移是通过一种复杂的化学机制实现的，其中涉及抗坏血酸。
