Self-Assembly Science

The Laboratory for Complex Energy Processes Self-Assembly Science Research Section

Professor : Masahiro KINOSHITA

We elucidate a variety of biological self-assembly and structureformation processes at molecular levels in a unified manner within the same theoretical framework.

(1) Nonlinear Behavior and Functioning Mechanism of Material Complex System

A material often exhibits high function when it is in contact with or mixed with another material. We refer to a system comprising multiple material constituents as a material complex system. Its typical examples are a biological system, colloidal suspension, and solid-liquid interface. The behavior of the system is far from the superposition of behaviors of its constituents and often highly functioning. The research on the system can lead to the exploration of novel technology and the development of new functioning materials. However, it requires the unification of research fields which have separately been systematized, and the collaboration of researchers in different fields is indispensible. In this research section, we have been collaborating with solid-state physicists, electrochemists,
and structural biologists on the metal-aqueous solution interface, drastic acceleration of chemical reactions within nanopores using the surface-induced phase transition, mechanism of RNA-protein recognition, and theoretical identification of thermostabilizing mutations for membrane proteins such as the G protein-coupled receptors (GPCRs).

(2) Theoretical Identification of Thermostabilizing Mutations for Membrane Proteins Such as G-protein Coupled Receptors (GPCRs)

GPCRs, transporters, and channels, which represent ~30% of the currently sequenced genomes, play imperative roles in sustaining life. Their malfunctioning causes a diversity of serious diseases. In particular, GPCRs are very important drug targets. However, due to their intrinsically low structural stability, it is difficult to determine their three-dimensional structures and/or to investigate the GPCR-drug binding modes. In this study, we are developing a reliable theoretical method based on statistical thermodynamics for identifying mutations leading to structural stabilization.

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(3) Unified Elucidation of Biological Self-Assembly and Ordering Processes

A variety of self-assembly processes (e.g., protein folding and association) and ordering processes (e.g., different types of molecular recognition, unidirectional movement of myosin along F-actin, and unidirectional rotation of the γ-subunit within F 1-ATPase) occur in biological systems. We wish to systematize a novel theory which enables us to elucidate them within the same framework in a unified manner. The temperature and pressure dependences and the effects of cosolvent and salt addition, which are common in these processes, provide a clue to the systematization. The key factor is the entropic effect originating from the translational displacement of water molecules coexisting with the biomolecules, in particular, biomoleculewater many-body entropic correlations. A hybrid of an integral equation theory and the morphometric approach originally developed by us is a major theoretical tool.

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