Dynamic cooperativity of molecular processes in active streaming, muscle contraction, and subcellular dynamics: the molecular mechanism of self-organization at the subcellular level.

Life phenomena are a kind of ordered dynamics appearing in macroscopic systems, living systems. Schrödinger has proposed a molecular mechanism for the organization of life phenomena, i.e., 'order-from-order' mechanism where ordered dynamics are composed of molecular dynamics having order as the ordered dynamics of a watch is caused by orderly movements of its mechanical elements. However, neither evidence supporting the 'order-from-order' mechanism has been found in living systems nor the reason why molecular dynamics acquire order instead of disorder has been elucidated for more than 30 years. The latter is quite anomalous from the point of views of thermodynamics, which is based on disordered behaviors of molecules. In this paper, we verify from studies of a streaming system reconstituted from rabbit skeletal F-actin and HMM that one life phenomenon, active streaming, is caused by the 'order-from-order' mechanism. This is also the case for muscle contraction. Moreover, it is probable that this mechanism generally works at the subcellular level, not only in biological motilities but also in life phenomena at biomembranes. We also clarify that dynamic cooperativity among molecule gives rise to order in molecular dynamics. Hence, dynamic cooperativity is the key mechanism for life phenomena caused by the 'order-from-order' principle at the subcellular level. To produce dynamic cooperativity it is necessary for component molecules or elements to have three states, i.e., inactive (stable) state 0, energized or energy storing (quasi-stable) state 1, and active (unstable) state 2. Each molecule performs elementary cycle 0 yields 1 yields 2 yields 0 repeatedly by using free energy at the molecular level. In a state far from thermodynamic equilibrium dynamic cooperativity is yielded in 2 yields 0 due to a kind of triggering action of neighboring elements and breaks thermodynamic detailed balance. In addition, dynamic cooperativity gives component molecules long-range interactions which depend on the structure of organelles or molecular assemblies. Dynamic cooperativity is able to decrease entropy production and will give a high efficiency in chemo-mechanical conversions. Great progress would be achieved in the understanding of the molecular mechanisms and thermodynamic principles of energy transformations in biological systems, if molecular dynamics during transformation could be directly observed. This is not only because physical changes accompanied by specific movements of macromolecules are essentially involved but also because such molecular movements play a substantial role in energy transformation. Entirely new ideas will be needed for this purpose although high voltage electron microscopy or X-ray diffraction, for instance, is now expected as to be one of the possible tools in the future. Fortunately even at present it is possible to obtain important information on molecular dynamics from biochemical and physiological data, if analyses are properly performed...