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[Objective]To explore the biological function of secreted protein AO-492 in the process of chitin induction from nematodetrapping fungus Arthrobotrys oligospora.[Method]The coding region of the main domain of chitinase AO-492 from A. oligospora was cloned and analyzed, and expressed in Pichia pastoris. The recombinant protein ReAO-Z492 was purified by nickel column affinity chromatography. The enzymatic activity of the recombinant protein under different temperature, pH and metal ion conditions was analyzed by NAG assay, and its biological function was analyzed by acting on Caenorhabditis elegans and eggs.[Result]The chitinase AO-492 had a signal peptide, no transmembrane domain, contained two chitin binding domains and a glycoside hydrolase 18 family domain, and the highly conserved substrate binding site of the glycoside hydrolase 18 family chitinase -SVGGWT- and the hydrolase active site -FDGGDLDWE-, as well as a typical TIM barrel molecular structure. Phylogenetic analysis showed that the protein had the closest genetic relationship with chitinase(EPS35099.1). SDS-PAGE and Western Blot analysis showed that the molecular weight of ReAO-Z492 was about 59 kD, which specifically reacted with mouse polyclonal antibody against A. oligospora. The optimal temperature and pH of ReAO-Z492 were 40℃ and 7.0, respectively. Mg2+ promoted the enzyme activity, while Ag+, Cu2+, Fe3+ and Zn2+ inhibited it. ReAO-Z492 had strong degrading activity on the body wall and egg shell of C. elegans.[Conclusion]The chitinase AO-492 of A. oligospora has a strong degradation effect on C. elegans and its eggs. [ABSTRACT FROM AUTHOR]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Engineering Geology / Gongcheng Dizhi Xuebao is the property of Journal of Engineering Geology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Hydrogeology & Engineering Geology / Shuiwendizhi Gongchengdizhi is the property of Hydrogeology & Engineering Geology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the meso-damage evolution law of rock under freeze-thaw environment, the red sandstone was taken as the research object. The freeze-thaw cycle test was firstly carried out, and then CT scanning was performed on the samples that experienced 0, 5, 10, 20 and 40 freeze-thaw cycles. The K-means clustering algorithm was used to realize the 2D pore identification of scanned images. The freeze-thaw failure mode of red sandstone was reproduced through 3D reconstruction, and the effective bearing volume of the sample was determined. The quantitative analysis of freeze-thaw damage of rock was realized at the meso-level. The results show that the threshold value can be determined by K-means clustering algorithm, and the binarization of CT images can be effectively achieved; 3D reconstructed model can reproduce the damage mode of red sandstone samples in the freeze-thaw process and the development characteristics of internal pores; with the increase of the number of freeze-thaw cycles, the damage variables based on the definition of effective bearing volume gradually increase and consistent with the development trend of pores, which can effectively reflect the damage evolution law of rock under the affect of freeze-thaw cycles, and provides a feasible method for the study of meso-damage of rock under freeze-thaw cycle. [ABSTRACT FROM AUTHOR]

In accordance with the occurrence characteristics and original defect properties for side slope with bedding rock mass，this paper studied the bifurcation behavior and stability behavior for side slope rock mass by using initial post-buckling theory and cusp catastrophic model, which derived its bifurcation equation and the calculation formula of bifurcation load, determined the upper and lower limit of buckling failure in a state of post-buckling, built the criteria for buckling failure of rock mass bedding slope, and presented an application with the example of Bawang mountain slope located the lower reaches of the Yalu River. The results indicate that the critical value at bifurcation point of the side slope with bedding rock mass is determined by its bifurcation set, the stability of the post-buckling equilibrium path and equilibrium configuration for side slope with bedding rock mass can be revealed by using initial post-buckling theory, and the threshold value of buckling failure can be obtained only if considering the actual defect for side slope with bedding rock mass. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The freeze-thaw cycling experiment was conducted for water-saturated sandstone under an open system to record the freeze-thaw deterioration process and failure characteristic of rock.And then the mechanical properties experiment with four kinds of confining pressures was carried out for sandstone on different freeze-thaw cycles (0,5,10,20,40 times).Subsequently,the influence law of freeze-thaw cycles and confining pressure on the physical and mechanical properties of rock was analyzed systematically.The result shows that the primary modes of freeze-thaw damage deterioration for sandstone are spalling mode,crack mode,shedding mode and fracture mode.With the increase of freeze-thaw cycles,the quality and density of rock samples present the trend of increasing at first and then decreasing,while the speed of the longitudinal wave decreases continuously.With the increase of confining pressure and the number of freeze-thaw cycles,the compaction property is enhanced gradually,the peak strain increases constantly,the plastic yield segment is becoming obviously,and the reduction rate of residual strength decreases,exhibiting the failure mode of enhanced ductility and weakened brittleness.While the elastic modulus,compressive strength and residual strength increase obviously with the increase of confining pressure,and decrease with the increase of freeze-thaw cycles.Through the nonlinear evolution of meso-structural damage,the rock displays the variation of macroscopic mechanical properties. [ABSTRACT FROM AUTHOR]