J-PARC (Japan Proton Accelerator Research Complex) is now under construction. The facility promises to deliver neutron intensities that are at least an order of magnitude (or more) higher than those at existing sources: traditional nuclear reactors such as JRR-3 in JAEA. New prospects for neutron in biology with use of a diffractometer (BIX-P1), small angle scattering (HI-SANS) and inelastic scattering spectrometer (DIANA) will be proposed. BIX-P1 will provide new insight of nature of the chemical bonds and molecular recognition mechanism in proteins on the basis of hydrogen and hydration in proteins. HI-SANS will open a new horizon for studying multi-component biological systems in whole hierarchal levels. DIANA will reveal the dynamical properties of proteins with relation to the hydration water and will be intensively used to direct the application such as drug design.

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Four decades have passed since linker histone H1 was discovered. In spite of many efforts, structural and functional roles of linker histone in the chromatin formation still remain to be elucidated. Notable studies related to linker histones have been reported recently, such as findings of specific roles in cell division, interaction modes of its globular domain with DNA and higher order structure of chromatin. The recent advance will be reviewed.

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Stochasticity of chemical reaction is particularly prominent in small systems, such as cells. Recent experimental and theoretical studies reveal that stochastic cellular reactions generate fluctuations, which affect the behaviors of downstream reactions. Here, I show how large each reaction generate fluctuation, and how large the fluctuation is amplified in the downstream reaction. I discuss the possibility that such propagating fluctuations convey information about reaction networks.

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We recently demonstrated that the conger eel galectins, Congerin I and II, have evolved under significant selective pressure, with the emergence of a new strand-swap structure between subunits in Congerin I. To understand the structure-thermostability relationship of Congerins, and seek clues to the mechanism of their evolution, we improved the thermostability of Congerin II by rational design and in vitro evolutionary protein engineering. A resulting Tyr16/Thr88 double mutant exhibited structural features and thermostability similar to the naturally thermostable isoform, Congerin I. Thus, under artificial selective pressure, Congerin II partially reproduced the natural evolution of Congerin I.

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Recent exponential increase of three-dimensional structural information by structural genomics revealed that a lot of proteins from hyper-thermophilic organisms have oligomeric structures. Based on these findings, it has been proposed that oligomerization is one of the strategies for enhancing thermostability of proteins in thermophilic organism. Here I describe how oligomerization contributes to the thermostability in protein L-isoaspartyl-O-methyltransferase from Sulfolobus tokodaii from its crystal structural and mutational analyses.

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In the biological system, various processes of the self-assembly and formation of ordered structure (e.g., protein folding, molecular recognition, association of protein molecules, and protein-membrane association) occur to sustain life. By referring to our results of analyses using statistical-mechanical theories, we argue that the entropic gain originating from the translational movement of water molecules play crucially important roles in these processes.

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