We investigated the relationship between whisker mechanoreceptive inputs and the neural responses to optical stimulation in layer 2/upper 3 (L2/U3) of the barrel cortex using optogenetics since, ideally, we should investigate interactions among inputs with spatiotemporal acuity. Sixteen whisker points of a transgenic rat (W-TChR2V4), that expresses channelrhodopsin 2 (ChR2)-Venus conjugate (ChR2V) in the peripheral nerve endings surrounding the whisker follicles, were respectively connected one-by-one with 16 LED-coupled optical fibres, which illuminated the targets according to a certain pattern in order to evaluate interactions among the inputs in L2/U3. We found that the individual L2/U3 neurons frequently received excitatory inputs from multiple whiskers that were arrayed in a row. Although the interactions among major afferent inputs ( MAI s) were negligible, negative interactions with the surrounding inputs suggest that the afferent inputs were integrated in the cortical networks to enhance the contrast of an array to its surroundings. With its simplicity, reproducibility and spatiotemporal acuity, the optogenetic approach would provide an alternative way to understand the principles of afferent integration in the cortex and should complement knowledge obtained by experiments using more natural stimulations.

Artificial creation of macroscopic motion triggered with structural change of small molecule is a challenging theme. In many approaches to create macroscopic motions, our salient points are in (1) using non-covalent assembly constructed in water, (2) actuation by small amount of synthesized molecular machine, (3) repeatability, and (4) spatially organized dynamics. To propagate the structural change of small molecules to macroscopic dynamics, intermolecular interaction is essential. However, simple interaction makes only simple behavior. To create highly hierarchical motion, organizations of cooperative interactions are necessary. In the symposium, mechanistic aspects of macroscopic motions of self-assemblies, in which water plays important roles, will be discussed. 2SDP-05 アクチンモノマーの会合と多価カチオンが媒介する同符号コ ロイド粒子間実効引力 Association of Actin Monomers and Effective Attraction between Like-Charged Colloidal Particles Mediated by Multivalent CationsRyo Akiyama (Dept. of Chem., Kyushu Univ.)Disassembly and assembly of actin filament change a cell shape and drive the motion of amoeba-like cell. Then, the association of actin monomer regulates this function. To discuss this association mechanism we studied the attractive interaction between macroanions mediated by multivalent cations using an integral equation theory with a simple model. The calculated results indicate that the effective attraction increases as the charge of macroanion becomes larger. This result supports a hypothesis of the regulation mechanics: The association is driven by the charge of monomer and the charge is regulated by the hydrolysis of ATP. We will discuss the detail of the scenario. 2SDP-06 タンパク質の構造ゆらぎと変化に対する相互作用成分解析 Interaction-Component Analysis on Protein Structure in Explicit Solvent Nobuyuki Matubayasi (Division of Chemical Engineering, Graduate School of Engineering Science, Osaka University)Using all-atom molecular dynamics simulation combined with a statisticalmechanical theory of solvation, the hydration effect is addressed on the structural fluctuation of cytochrome c in pure-water solvent. During the course of equilibrium fluctuation, the variation of the protein intramolecular energy is shown to be induced and compensated by the solvent water through the exchange of the electrostatic interaction energy. The urea effect on protein structure is also analyzed in terms of the transfer free energy from pure-water solvent to the urea-water mixed solvent. It is found that the transfer free energy correlates strongly with the change in the van der Waals interaction upon transfer and not with the change in the electrostatic interaction. The rodent whisker-barrel system has been an ideal model for studying somatosensory representations in the cortex. However, it remains a challenge to experimentally stimulate whiskers with a given pattern under spatiotemporal precision. Here we identified the selective expression of channelrhodopsin-2 (ChR2) in the large mechanoreceptive neurons in the trigeminal ganglion (TG) as well as their peripheral nerve endi...