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21AIST TODAY 2013-1Geological Survey and Applied GeoscienceAntifreeze protein of high activity produced from a snow mold fungus, Typhula ishikariensisCrystal structure of antifreeze protein from a snow mold fungusAntifreeze proteins (AFPs) preferentially adsorb to the surface of ice crystals, inhibiting their further growth. It is expected that AFPs can be applied to various industrial uses including frozen food and cold heat transfer. AFP from a psychrophilic fungus, Typhula ishikariensis (TisAFP) has been identified to exhibit ice growth inhibition effectively. In the present study, we determined the crystal structure of TisAFP and found that TisAFP is mainly composed of β-helical structure to fold into a semipear-like shape. In contrast to the other hyperactive AFPs with β-helical structures, there were much less repetitive residues aligned on the molecular surface of TisAFP. Site-directed mutational analysis revealed that the ice-binding site of TisAFP is located on the flattest surface of the molecule. In troughs of the ice-binding site there were aligned water molecules which seem to act as anchors for ice-binding. Fluorescence-based ice plane affinity analysis showed that TisAFP binds to both basal and prism planes of ice crystal, different from the other hyperactive AFPs. The unique feature of TisAFP that lacks the regularity in its ice-binding site provides the novel structural insight for hyperactive AFPs.Sakae TSUDAHidemasa KONDOBioproduction Research InstituteAIST TODAY Vol.12 No.12 p.13 (2012)(a) Three-dimensional structure of TisAFP, (b) Molecular surface of TisAFP (The ice-binding site (IBS) is drawn in yellow. Bound waters aligned at the ice-binding site are represented by blue balls.), (c) An illustration representing that TisAFP binds to the ice surface through the IBSMott transistor: a novel field effect transistor based on an electronic phase transitionElectrostatic controls of the metal-insulator transition of strongly correlated materials A Mott transition is a metal-insulator transition characteristic of strongly correlated electronic materials. Mott transistors based on an electrostatic triggering of the Mott transition are believed to surpass the conventional semiconductor FETs because of the vast functionalities and the intrinsically material-independent scaling limit. In this study, we have developed a prototype device of the Mott transistor with a CaMnO3 channel, a typical perovskite-type Mn oxide showing a Mott transition. In order to accumulate a large amount of carriers in the CaMnO3 channel, an electric double layer between the channel and ionic liquid was used for the gate dielectric. Gate voltage as small as 2 V was enough to induce a Mott transition and the insulating CaMnO3 channel changed to the metallic one drastically. Furthermore, gate-voltage dependence of the drain current showed large hysteresis, suggesting a potential application for novel nonvolatile memories.Schematic picture of a Mott transistor consisting of a compressive-strained CaMnO3 thin film and an example of the wiringAkihito SAWAIsao INOUEElectronics and Photonics Research InstituteShutaro ASANUMAInnovation Center for Advanced NanodevicesAIST TODAY Vol.12 No.10 p.16 (2012)Life Science and BiotechnologyGate-voltage dependence of the drain current in a CaMnO3-channel Mott transistor measured at room temperatureInformation Technology and Electronics a.b.c.3D structure ofTisAFPBound waters in the ice-binding siteSchematic model of TisAFP and iceIce surface+-CationDEME+GDS++++----Ionic liquidSepa-ratorCaMnO3channelIDSIGVDVGSubstrateAnion TFSI-D: DrainS:Source G:GateGate voltage (V)Drain current (μA)-2-10120.250.200.150.100.050.00

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