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Enantioselective hydrolysis of epoxides by epoxide hydrolase (EH) is one of the most attractive approaches for the synthesis of chiral epoxides. So far, attempts to develop an efficient epoxide hydrolase -mediated biotransformation have been limited by either the low activity or insufficient enantioselectivity of epoxide hydrolase. In this study, iterative saturation mutagenesis (ISM) of epoxide hydrolase from Agrobacterium radiobacter AD1 (ArEH) was performed for efficient production of (R)-epichlorohydrin. Six amino acid residues, I108, A110, D131, I133, T247, and G245, were selected for site saturation mutagenesis, and a sequential combination of positive mutants using ISM was constructed. Targeted mutagenesis generated five mutants (T247K, I108L, D131S, T247K/I108L, and T247K/I108L/D131S) with improved activity and enantioselectivity. Kinetics analysis showed that the best mutant, T247K/I108L/D131S, exhibited a 4.5-fold higher catalytic efficiency (k cat/K m) value and a 2.1-fold higher enantioselectivity (E value) towards epichlorohydrin than the wild-type (WT) enzyme. Molecular docking computations support the source of notably improved enantioselectivity. In addition, the triple mutant also displayed a significantly enhanced thermostability, with > 8-fold longer half-life at 50 °C than WT. A gram-scale kinetic resolution of (R,S)-epichlorohydrin was performed using T247K/I108L/D131S mutant as biocatalyst, affording a (R)-epichlorohydrin yield of 40.2% (> 99.9% enantiomeric excess) and an average productivity of 1410 g L−1 d−1. The engineered T247K/I108L/D131S variant is a promising biocatalyst for the enzymatic synthesis of (R)-epichlorohydrin.

Salt severely restricts cotton (Gossypium hirsutum) growth and production. The present study was undertaken to study the effect of salt-induced hydrogen peroxide (H2O2) on antioxidant enzymes in cotton. NaCl treatment or exogenous H2O2 was used to investigate the relationship between H2O2 content and levels of antioxidant enzymes including superoxide dismutase (SOD), ascorbate peroxidase (APX), peroxidase (POD), and catalase (CAT), as well as the transcriptional levels of corresponding genes. H2O2 content increased within 24 h following 200 mmol L–1 NaCl treatment. Both NaCl-induced and exogenous H2O2 increased the activity of antioxidant enzymes including APX and SOD and upregulated the transcriptional levels of GhcAPX1, GhFeSOD, and GhchlCSD. These increased activities and upregulated transcriptional levels were inhibited when the salt-induced H2O2 was scavenged by NAC. These results indicate that salt-induced H2O2 as a second signaling messenger modulates APX and SOD activities by regulating the transcription levels of corresponding genes, alleviating oxidative stress, and increasing salt tolerance in cotton.

To improve the operational stability and reusability of an epoxide hydrolase (EH) for the biosynthesis of optically active epoxides. A covalently immobilization strategy was employed to improve the stability of Agrobacterium radiobacter EH by using ethylenediamine (EDA)-functionalised epoxy resin LX-1000EP as carrier. Under the optimal conditions, the activity recovery of immobilized enzyme was 72 % and the specific activity was 634 U/g. Immobilized EH exhibited significantly enhanced thermal stability with a half-life of more than 6.8-fold at 50 °C than that of the free enzyme. A gram-scale kinetic resolution of (R,S)-epichlorohydrin using immobilized preparation as biocatalyst was performed and (R)-epichlorohydrin was obtained with 35 % yield and 99 % enantiomeric excess. The immobilized EH showed good operational stability and even after six reactions, it retained >85 % of the initial activity. The operational stability and recyclability of immobilized EH on an EDA-functionalized epoxy supports demonstrated its potential for producing (R)-epichlorohydrin.

In this paper, novel photocatalysts were prepared by PO 4 3− and PO 4 3− /SO 4 2− surface modification of TiO 2 . Photocatalytic activities of these photocatalysts as affected by preparation conditions were studied by examining the degradation of aqueous methylthionine chloride solution. Their properties were measured and compared by XRD, IR and UV. The experimental results indicate that the modification of TiO 2 by PO 4 3− and PO 4 3− –SO 4 2− enhance distinctly its photocatalytic activity, especially the PO 4 3− –SO 4 2− /TiO 2 . The synergistic effect of photocatalytic decomposition and surface acidity of catalyst is observed by optimized the ratio of PO 4 3− and SO 4 2− . Super acidification of TiO 2 increases the absorbance of catalyst in ultraviolet region, and improves distinctly the photocatalytic activity on 365 nm light.

Shallow-depth acoustic reflection profiling survey has been conducted on the Tanlu fault zone in Laizhou Bay. It is found that the Tanlu fault zone is obviously active during the late Quaternary and it is still the dominating structure in this region. The Tanlu fault zone consists of two branches. The KL3 fault of the western branch is composed of several high angle normal faults which had been active during the period from the the latest Pleistocene to early Holocene, dissected by a series of northeast or approximate east-west trending fault which leaped sediment of the late Pleistocene. The Longkou fault of the eastern branch consists of two right-laterally stepped segments. Late Quaternary offsets and growth strata developed along the Tanlu fault zone verify that the fault zone retained active in the latest Pleistocene to the early Holocene. The Anqiu-Juxian fault that passes through the middle of Shandong and corresponds to the Longkou fault is composed of a series of right-laterally stepped segments. The active faults along the eastern branch of the Tanlu fault zone from the Laizhou bay to the north of Anqiu make up a dextral simple shear deformation zone which is characterized by right-lateral strike-slip movement with dip-slip component during the late Quaternary.

A nonlinear magnitude frequency equation has been derived in this paper on the assumption that all seismicity systems hold fractal characteristics, and according to the differences of relevant coefficients in the equation, seismicity systems are classified into two types: type I, the whole earthquake activity is controlled by only one great unified system; type II, the whole earthquake activity is controlled by more than one great system. One type of seismicity system may convert to the other type, generally. For example, a type I system will change to a type II system prior to the occurrence of a strong earthquake in North China. This change can be regarded as an index for earthquake trend estimation. In addition, the difference between b value in nonlinear magnitude frequency equation and that in linear equation and the term dΔM related to the coefficients of nonlinear terms obtained in this paper are proved to be a pair of available parameters for medium short term earthquake prediction.

Recent studies of the northeastern part of the Tibetan Plateau have called attention to two emerging views of how the Tibetan Plateau has grown. First, deformation in northern Tibet began essentially at the time of collision with India, not 10-20 Myr later as might be expected if the locus of activity migrated northward as India penetrated the rest of Eurasia. Thus, the north-south dimensions of the Tibetan Plateau were set mainly by differences in lithospheric strength, with strong lithosphere beneath India and the Tarim and Qaidam basins steadily encroaching on one another as the region between them, the present-day Tibetan Plateau, deformed, and its north-south dimension became narrower. Second, abundant evidence calls for acceleration of deformation, including the formation of new faults, in northeastern Tibet since ~15 Ma and a less precisely dated change in orientation of crustal shortening since ~20 Ma. This reorientation of crustal shortening and roughly concurrent outward growth of high terrain, which swings from NNE-SSW in northern Tibet to more NE-SW and even ENE-WSW in the easternmost part of northeastern Tibet, are likely to be, in part, a consequence of crustal thickening within the high Tibetan Plateau reaching a limit, and the locus of continued shortening then migrating to the northeastern and eastern flanks. These changes in rates and orientation also could result from removal of some or all mantle lithosphere and increased gravitational potential energy per unit area and from a weakening of crustal material so that it could flow in response to pressure gradients set by evolving differences in elevation. Key Points The north-south limits of Tibet were set by lateral variations in strength Roughly 15 million years ago, deformation of NE Tibet accelerated Since 20-15 million years ago, the orientation of shortening rotated eastward ©2013. American Geophysical Union. All Rights Reserved.