Tabony J, Pochon N, Papaseit C
Commissariat a l'Energie Atomique, Departement de Biologie Moleculaire et Structurale, Laboratoire de Resonanc Magnetique en Biologie Metabolique, C.E.A. Grenoble, France.
Adv Space Res. 2001;28(4):529-35. doi: 10.1016/s0273-1177(01)00381-7.
The molecular processes by which gravity is transduced into biological systems are poorly, if at all, understood. Under equilibrium conditions, chemical and biochemical structures do not depend upon gravity. It has been proposed that biological systems might show a gravity dependence by way of the bifurcation properties of certain types of non-linear chemical reactions that are far-from-equilibrium. We have found that in-vitro preparations of microtubules, an important element of the cellular cytoskeleton, show this type of behaviour. On earth, the solutions show macroscopic self-ordering, and the morphology of the structures that form depend upon the orientation of the sample with respect to gravity at a critical moment at an early stage in the development of the self-organised state. An experiment carried out in a sounding rocket, showed that as predicted by theories of this type, no self-organisation occurs when the microtubules are assembled under low gravity conditions. This is an experimental demonstration of how a very simple biochemical system, containing only two molecules, can be gravity sensitive. At a molecular level this behaviour results from an interaction of gravity with macroscopic concentration and density fluctuations that arise from the processes of microtubule contraction and elongation.
重力转化为生物系统的分子过程，即便有人了解，也知之甚少。在平衡条件下，化学和生化结构并不依赖于重力。有人提出，生物系统可能通过某些远离平衡的非线性化学反应的分岔特性来表现出对重力的依赖性。我们发现，细胞骨架的重要组成部分微管的体外制剂表现出这种行为。在地球上，溶液呈现出宏观的自排序现象，并且在自组织状态发展的早期关键阶段，形成的结构形态取决于样品相对于重力的取向。在探空火箭上进行的一项实验表明，正如这类理论所预测的那样，当微管在低重力条件下组装时，不会发生自组织现象。这是一个仅包含两种分子的非常简单的生化系统对重力敏感的实验证明。在分子层面，这种行为是由重力与微管收缩和伸长过程中产生的宏观浓度和密度波动相互作用导致的。
