Self-Organization Phenomena in Active Streamings and Subcellular Dynamics

Abstract

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., an 'order-from-order' mechanism where ordered dynamics are composed of ordered molecular dynamics, much as the ordered dynamics of a watch is caused by orderly movements of its mechanical elements. In this paper we verify from studies on artificial active streamings in a streaming system reconstituted from rabbit skeletal F-actin and heavy meromyosin that one life phenomenon, active streaming, is caused by the 'orderfrom-order' mechanism. This will be also the case for muscle contraction. Moreover, it is probable that this mechanism generally works in biological motilities. We also clarify that dynamic cooperativity among molecules 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 the elementary cycle 0→1→2→0 repeatedly by using free energy at the molecular level. In a state far from thermodynamic equilibrium, dynamic cooperativity is yielded in 2→0 due to a kind of triggering action of neighborillg elements and breaks the thermodynamic detailed balance. In addition, dynamic cooperativity gives component molecules long-range correlations which depend on the structure of organelles or molecular assemblies. Dynamic cooperativity will give a high efficiency in chemomechanical conversions.