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Chemo-enzymatic route for chloramphenicol.

Pancreatic cancer (PC) is an aggressive human cancer. Appropriate methods for the diagnosis and treatment of PC have not been found at the genetic level, thus making epigenetics a promising research path in studies of PC. Histone methylation is one of the most complicated types of epigenetic modifications and has proved crucial in the development of PC. Histone methylation is a reversible process regulated by readers, writers, and erasers. Some writers and erasers can be recognized as potential biomarkers and candidate therapeutic targets in PC because of their unusual expression in PC cells compared with normal pancreatic cells. Based on the impact that writers have on the development of PC, some inhibitors of writers have been developed. However, few inhibitors of erasers have been developed and put to clinical use. Meanwhile, there is not enough research on the reader domains. Therefore, the study of erasers and readers is still a promising area. This review focuses on the regulatory mechanism of histone methylation, and the diagnosis and chemotherapy of PC based on it. The future of epigenetic modification in PC research is also discussed.

The recombinant rAgaZC-1 was a family GH50 β-agarase from Vibrio sp. ZC-1 (CICC 24670). In this paper, the mutant D622G (i.e., mutate the aspartic acid at position 622 to glycine) had better thermo-stability than rAgaZC-1, showing 1.5℃ higher T5010 (the temperature at which the half-time is 10 min) and 4-folds of half-time at 41℃, while they had almost same optimum temperature (38.5℃), optimum pH (pH6.0) and catalytic efficiency. Thermal deactivation kinetical analysis showed that D622G had higher activation energy for deactivation, enthalpy and Gibbs free energy than rAgaZC-1, indicating that more energy is required by D622G for deactivation. Substrate can protect agarase against thermal inactivation, especially D622G. Hence the yield of agarose hydrolysis catalyzed by D622G was higher than that by rAgaZC-1. The models of D622G and rAgaZC-1 predicted by homology modeling were compared to find that it is the improved distribution of surface electrostatic potential, great symmetric positive potential and more hydrophobic interactions of D622G that enhance the thermo-stability.

L-Threonine transaldolase (LTTA) is a putative serine hydroxymethyltransferase (SHMT) that can catalyze the trans-aldehyde reaction of L-threonine and aldehyde to produce L-threo-β-hydroxy-α-amino acids with excellent stereoselectivity. In the present study, an L-threonine transaldolase from Pseudomonas sp. (PsLTTA) was mined and expressed in Escherichia coli BL21 (DE3). A substrate spectrum assay indicated that PsLTTA only consumed L-threonine as the donor substrate and could accept a wide range of aromatic aldehydes as acceptor substrates. Among these substrates, PsLTTA could catalyze p-methylsulfonyl benzaldehyde and L-threonine to produce L-threo-p-methylsulfonylphenylserine with a high conversion rate (74.4%) and a high de value (79.9%). The conversion and stereoselectivity of PsLTTA were found to be dramatically influenced by the concentration of the whole cell, the co-solvent and the reaction temperature. Through conditional optimization, L-threo-p-methylsulfonylphenylserine was obtained with 67.1% conversion and a near-perfect de value (94.5%), the highest stereoselectivity for an L-threo-β-hydroxy-α-amino acid so far reported by enzymatic synthesis. Finally, synthesis of L-threo-p-methylsulfonylphenylserine at a 100 mL scale by whole-cell biocatalysis was conducted. This is the first systematic report of L-threonine transaldolase as a robust biocatalyst for preparation of β-hydroxy-α-amino acids, which can provide new insights for β-hydroxy-α-amino acids synthesis.

The relationship between unfolding and inactivation of Hypocrea orientalis β-glucosidase has been investigated for the first time. The secretion of β-glucosidase from H. orientalis is induced by raw cassava residues. The enzyme was 75 kD without glycosylation. Guanidine hydrochloride (GuHCl) could reversibly inactivate the enzyme with an estimated IC50 value of 0.4 M. The inactivation kinetics model by GuHCl has been established and the microscopic inactivation rate constants are determined. The values of forward inactivation rate constants of free enzyme are found to be larger than that of substrate–enzyme complex suggesting the enzyme could be protected by substrate during denaturation. Conformational change of the enzyme during denaturation is observed as the intrinsic fluorescence emission peaks appeared red-shift (334–354 nm) with intensity decreased following increase of GuHCl concentrations. Inactivation extent is found to be greater than conformation change of the whole enzyme, indicating that the active site of H. orientalis β-glucosidase might be a more flexible region than the whole enzyme.

Penicillin V is a bacteriolytic β-lactam antibiotic drug. In the present work, we investigated the inhibitory effect of Penicillin V on the activity of mushroom tyrosinase for the first time. The molecular mechanism for the inhibition of tyrosinase by Penicillin V was investigated by means of kinetics analysis, fluorescence quenching and molecular docking techniques. The results showed that Penicillin V could inhibit both monophenolase and diphenolase activities with IC50 of 16.6 ± 0.5 and 11.0 ± 0.2 mmol/L, respectively. The inhibitory type of Penicillin V on mushroom was mixed type, and the values of KI and KIS were 13.46 and 17.26 mmol/L, respectively. The fluorescence quenching and molecular docking showed that Penicillin V could form static interaction near the catalytic pocket of the enzyme to hinder the transportation of substrate to the active site, as well as reduce the copper plasticity for catalysis. Our results contributed to the usage of Penicillin V as a novel tyrosinase inhibitor with dual effect in field of antimicrobial and food preservation and could also provide guidance for the design of novel tyrosinase inhibitors.

L-threonine aldolase (LTA) is a PLP-dependent enzyme that can reversibly catalyze aldol reaction of glycine and acetaldehyde to produce β-hydroxy-α-amino acids. In the present work, a putative lta gene from Actinocorallia herbida (AhLTA) was mined and over-expressed in Escherichia coli BL21 (DE3). The substrate spectrum assay indicated that AhLTA only used glycine as donor substrate and tolerated a wild range of aromatic aldehydes as acceptor substrates. It was found that the type and position of substituents in the aromatic aldehydes exerted a significant impact on the activity and stereoselectivity at β-carbon of AhLTA. Among those substrates, AhLTA could catalyze glycine and 4-methylsulphonyl benzaldehyde (14a) to produce L-threo-4-methylsulfonylphenylserine ((2S,3R)-14b) with high conversion (94.4%) and moderate stereoselectivity (19% de). By conditional optimization, the de value of (2S, 3R)-14b was improved to 61% and the conversion was 75%. Taken together, our study suggested that AhLTA might be a promising catalyst for producing chiral β-hydroxy-α-amino acids.

White-rot fungus Cerrena sp. strain HYB07 produces laccase with high yields and strong decolorization ability. Cerrena laccase was immobilized by preparing cross-linked enzyme aggregates (CLEAs), and ammonium sulfate and glutaraldehyde were the optimal precipitant and cross-linking agent, respectively. An activity recovery rate of 68.1% was obtained at pH 8 after precipitation with (NH 4 ) 2 SO 4 and cross-linking with 30 mM glutaraldehyde for 3 h at 25 oC. Immobilized Cerrena laccase demonstrated improved tolerance to NaCl, metal ions and organic solvents. NaCl was a mixed-type inhibitor of both free and immobilized laccases with 2, 2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) as the substrate, and the improvement of NaCl resistance by laccase immobilization was quantified kinetically. Laccase CLEAs had higher inhibition constants K I and K IS compared to free laccase, suggesting that the affinity of NaCl to laccase was attenuated by immobilization. Laccase CLEAs also displayed greater velocity and efficiency in Remazol Brilliant Blue Reactive decolorization in the presence of NaCl than free laccase. Greater differences in the half time ( t 1/2 ) of Remazol Brilliant Blue Reactive decolorization by free and immobilized laccases were observed with increasing NaCl concentrations.

Thermal inactivation kinetics of Hypocrea orientalis β-glucosidase and effect of glucose on thermostability of the enzyme have been determined in this paper. Kinetic studies showed that the thermal inactivation was irreversible and first-order reaction. The microscopic rate constants for inactivation of free enzyme and substrate-enzyme complex were both determined, which suggested that substrates can protect β-glucosidase against thermal deactivation effectively. On the other hand, glucose was found to protect β-glucosidase from heat inactivation to remain almost whole activity below 70°C at 20mM concentration, whereas the apparent inactivation rate of BG decreased to be 0.3×10(-3)s(-1) in the presence of 5mM glucose, smaller than that of sugar-free enzyme (1.91×10(-3)s(-1)). The intrinsic fluorescence spectra results showed that glucose also had stabilizing effect on the conformation of BG against thermal denaturation. Docking simulation depicted the interaction mode between glucose and active residues of the enzyme to produce stabilizing effect.

Relying on magnetron sputtering technology, a Polytetrafluoroethylene (PTFE) thin film was deposited on silicon substrate. We systematically investigated the atomic bonding, growth mode, and surface morphology of the as-prepared PTFE thin films by different nominal deposition power with different thicknesses. The mechanical properties including elastic modulus, hardness, strain rate sensitivity and creep resistance were carefully detected in a thick (1270 nm) PTFE film by an instrumental nanoindentation. In comparison to its bulk counterpart, PTFE thin film owns much higher elastic modulus and stronger resistances to the plastic and time-dependent plastic deformation. The results of its chemistry and mechanical properties show the films are hydrophobic and of higher mechanical strength. The enhanced mechanical properties of PTFE thin film could be intrinsically tied to its complex fluorocarbon groups which generated from the breakage and re-organization of C-F chains during sputtering process. The creep resistance of PTFE thin film was approximately two times stronger than the bulk PTFE.

A digital PWM controller based on FPGA with the voltage feedback control mode is designed. The function blocks and the timing of the digital controller are introduced. The controller is applied in Buck circuits to verify the system function. The experimental results show that the designed controller has fast and strong real-time response speed with high reliability, which prove the correct theoretical analyses and feasibility of the proposed method.

The Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, also called the Guo Shou Jing Telescope) is a special reflecting Schmidt telescope. LAMOST's special design allows both a large aperture (effective aperture of 3.6 m–4.9 m) and a wide field of view (FOV) (5°). It has an innovative active reflecting Schmidt configuration which continuously changes the mirror's surface that adjusts during the observation process and combines thin deformable mirror active optics with segmented active optics. Its primary mirror (6.67 m × 6.05 m) and active Schmidt mirror (5.74m × 4.40m) are both segmented, and composed of 37 and 24 hexagonal sub-mirrors respectively. By using a parallel controllable fiber positioning technique, the focal surface of 1.75 m in diameter can accommodate 4000 optical fibers. Also, LAMOST has 16 spectrographs with 32 CCD cameras. LAMOST will be the telescope with the highest rate of spectral acquisition. As a national large scientific project, the LAMOST project was formally proposed in 1996, and approved by the Chinese government in 1997. The construction started in 2001, was completed in 2008 and passed the official acceptance in June 2009. The LAMOST pilot survey was started in October 2011 and the spectroscopic survey will launch in September 2012. Up to now, LAMOST has released more than 480000 spectra of objects. LAMOST will make an important contribution to the study of the large-scale structure of the Universe, structure and evolution of the Galaxy, and cross-identification of multi-waveband properties in celestial objects.

This paper describes the data release of the LAMOST pilot survey, which includes data reduction, calibration, spectral analysis, data products and data access. The accuracy of the released data and the information about the FITS headers of spectra are also introduced. The released data set includes 319 000 spectra and a catalog of these objects.

In order to optimize the cellulase (from Aspergillus glaucus) hydrolysis of pretreated rice straw, the effects of varying enzyme concentration, temperature, and pH were studied. The best experimental conditions found to degrade the pretreated rice straws were 24 h of incubation at 55 °C and pH 5.0, with an enzyme concentration of 48 mg/L. Urea is one of the important nitrogen sources used in fungi culture, but it is also a denaturant. The model of denaturation of endoglucanase (EG) in urea solutions was established. The denaturation was a slow, reversible reaction. Determination of microscopic rate constants showed k(+0)k'(+0), indicating that EG was protected by the substrate to a certain extent during denaturation. Comparison with the results from fluorescence emission spectroscopy revealed that the inactivation of EG occurred before the marked conformational changes could be detected.

The Large sky Area Multi-Object Spectroscopic Telescope (LAMOST) General Survey is a spectroscopic survey that will eventually cover approximately half of the celestial sphere and collect 10 million spectra of stars, galaxies and QSOs. Objects both in the pilot survey and the first year general survey are included in the LAMOST First Data Release (DR1). The pilot survey started in October 2011 and ended in June 2012, and the data have been released to the public as the LAMOST Pilot Data Release in August 2012. The general survey started in September 2012, and completed its first year of operation in June 2013. The LAMOST DR1 includes a total of 1202 plates containing 2,955,336 spectra, of which 1,790,879 spectra have observed signal-to-noise S/N >10. All data with S/N>2 are formally released as LAMOST DR1 under the LAMOST data policy. This data release contains a total of 2,204,696 spectra, of which 1,944,329 are stellar spectra, 12,082 are galaxy spectra and 5,017 are quasars. The DR1 includes not only spectra, but also three stellar catalogues with measured parameters: AFGK-type stars with high quality spectra (1,061,918 entries), A-type stars (100,073 entries), and M stars (121,522 entries). This paper introduces the survey design, the observational and instrumental limitations, data reduction and analysis, and some caveats. Description of the FITS structure of spectral files and parameter catalogues is also provided., 39 pages, 13 figures

Active optics is the most difficult part in LAMOST project. Especially for the segmented reflecting Schmidt plate Ma, in which both segmented mirror active optics and thin mirror (or deformable mirror) active optics are applied. To test and optimize the thin mirror active optics of Ma, and to approach the reality of operating environment of the telescope, an outdoor experiment system has been established. This experiment system is also a ‘small LAMOST’ with one sub-mirror of the primary mirror Mb and one sub-mirror of the Schmidt plate Ma, and with full scale in spacing (40 meters) between Ma and Mb. many parts of LAMOST were tested in the experiment system except segmented mirror active optics. Especially for force actuators, thin mirror support system, friction driving of the alt-azimuth mounting and its control system, wave front test along such a long optical path. This paper presents the experiment system, research and developments, and some experiment results.