チュウトウド コウネツセイ サイキン Geobacillus stearothermophilus セイイク オンド ヘンイカブ ニ オケル タンパクシツ ハツゲン カイセキ

Optimum growth of moderately thermophile Geobacillus stearothermophilus (Bst) has been observed at 55ºC, and suppressed by the downshift to lower temperature. In order to understand the relationship between growth temperature and protein expression, we made Bst mutant strains which were adapted to lower temperature (30ºC) compared with wild type strain, and then we examined their protein expression under various growth temperatures. When they were cultured at 55ºC, different expression patterns of six proteins (P1-P6) were observed between wild type and mutant strains, whereas five proteins (A1-A5) were found only in mutant strains cultured at 37ºC. Furthermore, expression of five proteins (DS1-DS5) was increased according to the downshift of growth temperature to 37ºC. Among all 16 proteins, abundant three proteins (P1, DS3, and DS5) were electroblotted to PVDF membrane, followed by analyzed N-terminal amino acid sequences. As a result, it was suggested that P1 must be Surface-layer protein A (sbsA), whereas DS3 and DS5 were unknown proteins

Molecular dynamics simulations on interaction between dislocation and Y2O3 nanocluster in FE

For a new insight on the mechanical properties of oxide dispersion strengthened (ODS) steels from atomistic viewpoints, we have implemented molecular dynamics simulations on the interaction between Y2O3 nanocluster and dislocation in bcc Fe. There is so far no all-round interatomic potential function that can represent all the bonding state, i.e. metal, ion and covalent systems, so that we have adopted rough approximation. That is, each atom in Y2O3 is not discriminated but treated as “monatomic” pseudo-atom; and its motion is represented with the simple pairwise potential function as same as Johnson potential for Fe. The potential parameters are fitted to the energy change in the hcp infinite crystal, by using the ab-initio density functional theory(DFT) calculation for explicitly discriminated Y and O. We have set edge/screw dislocation in the centre of periodic slab cell, and approached it to the “YO” monatomic nano-cluster coherently precipitated in bcc-Fe matrix. The dislocation behavior is discussed by changing the size and periodic distance of the nano-cluster. Among the many useful results, we have obtained a conclusion that the edge dislocation is strongly trapped by YO sphere larger than the diameter of d =0 .9nm, while the screw dislocation shows various behavior, e.g. it cuts through the precipiate without remarkable resistance if the dislocation line tension is high, or it changes the slip plane leaving jogs at the position anterior to the precipiate with loose line tensio

Three-dimensional shapes and distributions of long-period stacking ordered structures in Mg₉₇Zn₁Gd₂ cast alloys characterized by electron tomography

Three-dimensional (3D) configurations of 14H long-period stacking ordered (LPSO) structures formed in Mg97Zn1Gd2 cast alloys at intermediate stages of the formation process have been studied by single tilt-axis electron tomography using high-angle annular dark-field scanning transmission electron microscopy. Lateral morphology of the 14H LPSO is clearly visualized by reconstructing 3D volumes. An existence of "dent-shaped" area was found in a 3D reconstructed volume for the first time. The edge of LPSO shows a characteristic triangular shape with an angle of 60°, which indicates that the growth front is parallel to {112¯0}Mg. It is suggested that in-plane irregular or characteristic shapes are related to the lateral growth mechanism of LPSO. Electron tomography has proven to be an indispensable tool to characterize in-plane structural information of LPSO formed in α-Mg matrix

Quantum gapped state in a spin-1/2 distorted honeycomb-based lattice with frustration

We successfully synthesized ($p$-Py-V)[Cu(hfac)$_2$], a verdazyl-based complex. Molecular orbital calculations revealed five types of intermolecular interactions between the radical spins and two types of intramolecular interactions between the radical and the Cu spins, resulting in a spin-1/2 distorted honeycomb-based lattice. Additionally, competing ferromagnetic and antiferromagnetic (AF) interactions induce frustration. The magnetization curve displayed a multistage increase, including a zero-field energy gap. Considering the stronger AF interactions that form dimers and tetramers, the magnetic susceptibility and magnetization curves were qualitatively explained. These findings demonstrated that the quantum state, based on the dominant AF interactions, was stabilized due to the effects of frustration in the lattice. Hence, the exchange interactions forming two-dimensional couplings decoupled, reducing energy loss caused by frustration and leading to frustration-induced dimensional reduction.Comment: 6 pages, 5 figure

アミトロール テイコウセイ ダイチョウキン カブ ニオケル タンパクシツ ハツゲン カイセキ

It was reported that the E.coli mutant strain exhibited the resistance against amitrole (AT) which had used as a pesticide and inhibits the bacterial growth. In order to elucidate the mechanism on the AT-resistance in E.coli, we prepared the E.coli mutant strain by treating with chemical mutagen, MNNG, and then selected the AT-resistant E. coli strain. The obtained mutant strain was possible for proliferating even in the M9 minimal medium containing 2 mg/ml AT. Therefore, we examined the expressed proteins in the mutant strain, which was cultured under various conditions. As a result, it was suggested the expression of 22 kDa protein (P1) was suppressed as the AT concentration was increased in M9 medium. By the amino acid sequence analysis, it was proved that P1 must be alkyl hydroperoxide reductase C22 protein (ahpC). On the other hand, the expression of P2 protein in mutant strain has increased in the M9 medium containing 2mg/ml AT, and partial amino acid sequence of P2 was consistent with zinT (yodA) protein. From these results, it is likely that the amitrole-resistance in E.coli might be regulated by soxRS regulon, not oxy R, like adaptation for the oxidative stress

Threonine 138 is crucial for the Quaternary Structure and the Thermostability of Thermus thermophilus Inorganic Pyrophosphatase.

Inorganic pyrophosphatase (EC. 3.6.1.1) from Thermus thermophilus (Tth PPase) forms the thermostable hexamer，and it was suggested from X-ray studies that its intersubunit interactions stabilize the whole molecule. However，the contribution of Thr138 at the intertrimer interface to quatemary structure and thermostability was unknown functionally. Therefore，we prepared four Thr138-substituted variants (T138A，V ，N ，and H) by site-directed mutagenesis. Then，thermostabilities of the enzyme activity and the quatemary structure for T138V and A were decreased relative to those of the wild type Tth PPase，whereas T138H and N variants remained much hexamer contents and the enzyme activity than T138V and A. Therefore，we suggest that the polar group in Thr138 of Tth PPase is more crucial than the methyl group for thermostability and quatemary structure，and it may contribute to the formation of stable trimer-trimer interface