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Huaixu Cheng,Zhidan Luo,Mingsheng Lu,Song Gao,Shujun Wang 한국미생물학회 2017 The journal of microbiology Vol.55 No.5
The hyperthermophilic α-amylase from Thermococcus sp. HJ21 does not require exogenous calcium ions for thermostability,and is a promising alternative to commercially availableα-amylases to increase the efficiency of industrial processeslike the liquefaction of starch. We analyzed the aminoacid sequence of this α-amylase by sequence alignments andstructural modeling, and found that this α-amylase closelyresembles the α-amylase from Pyrococcus woesei. The geneof this α-amylase was cloned in Escherichia coli and the recombinantα-amylase was overexpressed and purified witha combined renaturation-purification procedure. We confirmedthermostability and exogenous calcium ion independencyof the recombinant α-amylase and further investigatedthe mechanism of the independency using biochemical approaches. The results suggested that the α-amylase has a highcalcium ion binding affinity that traps a calcium ion that wouldnot dissociate at high temperatures, providing a direct explanationas to why the addition of calcium ions is not requiredfor thermostability. Understanding of the mechanism offersa strong base on which to further engineer properties of thisα-amylase for better potential applications in industrial processes.
Pressure-Induced Confined Metal from the Mott InsulatorSr3Ir2O7
Ding, Yang,Yang, Liuxiang,Chen, Cheng-Chien,Kim, Heung-Sik,Han, Myung Joon,Luo, Wei,Feng, Zhenxing,Upton, Mary,Casa, Diego,Kim, Jungho,Gog, Thomas,Zeng, Zhidan,Cao, Gang,Mao, Ho-kwang,van Veenendaal, American Physical Society 2016 Physical Review Letters Vol.116 No.21
<P>The spin-orbit Mott insulator Sr3Ir2O7 provides a fascinating playground to explore insulator-metal transition driven by intertwined charge, spin, and lattice degrees of freedom. Here, we report high-pressure electric resistance and resonant inelastic x-ray scattering measurements on single-crystal Sr3Ir2O7 up to 63-65 GPa at 300 K. The material becomes a confined metal at 59.5 GPa, showing metallicity in the ab plane but an insulating behavior along the c axis. Such an unusual phenomenon resembles the strange metal phase in cuprate superconductors. Since there is no sign of the collapse of spin-orbit or Coulomb interactions in x-ray measurements, this novel insulator-metal transition is potentially driven by a first-order structural change at nearby pressures. Our discovery points to a new approach for synthesizing functional materials.</P>