High-level expression, purification, polyclonal antibody preparation against recombinant OprD from Pseudomonas aeruginosa

OprD is a specific porin which can binds imipenem and carbapenems in Pseudomonas aeruginosa. OprD loss plays a central role in mediating carbapenem resistance. Therefore, purification of oprD protein lays a pavement for the study in vivo and in vitro. In our study, the oprD gene was cloned into pQE30 expression vector, in frame with a sequence coding an N-terminal hexahistidine tag to allow purification by Ni2+ column. The recombinant OprD-6His was overproduced in inclusion form in Escherichia coli M15. OprD-6His was purified under denatured conditions using Ni-NTA conjugates. Antiserum against this recombinant OprD-6His protein was prepared in rabbit. Western blot analysis and enzyme linked immunosorbent assay (ELISA) were carried out to identify the reaction abilities and sensitivity of anti-OprD-6His polyclonal antibody to purified OprD-6His. Our results indicated that it was induction of E. coli M15 cells with 0.5 mM of isopropylthio-d-galactoside (IPTG) at 33°C for 4 h that the predicted 48 kDa OprD-6His fusion protein was expressed as the form of inclusion bodies with about 55-65 mg of OprD-6His per liter of culture. Western blot showed that recombinant OprD-6His protein could be identified by self-developed  anti-OprD-6His polyclonal antibody. Anti-OprD-6His polyclonal antibody was detectable with 1000 times dilution of the original polyclonal antibody solution. In conclusion, higher level expression of OprD was available in the pQE30 expression system at optimal condition. Self-prepared polyclone antibody can effectively detect difference of porin expression in P. aeruginosa with higher sensitivity and specificity.Key words: Pseudomonas aeroginosa; OprD; polyclonal antibody

A fast algorithm to estimate generation capacity tripped by emergency control for transient stability of large power system

2008-2009 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

The optical microscopy with virtual image breaks a record: 50-nm resolution imaging is demonstrated

We demonstrate a new 'microsphere nanoscope' that uses ordinary SiO2 microspheres as superlenses to create a virtual image of the object in near field. The magnified virtual image greatly overcomes the diffraction limit. We are able to resolve clearly 50-nm objects under a standard white light source in both transmission and reflection modes. The resolution achieved for white light opens a new opportunity to image viruses, DNA and molecules in real time

Interfacial magnetic vortex formation in exchange-coupled hard-soft magnetic bilayers

The exchange coupling between a hard magnetic layer MnBi and a soft magnetic layer Co-Fe has been found to significantly improve the maximum energy product. In this work, the spin structure of exchange-coupled MnBi:Co-Fe bilayers is experimentally investigated by X-ray magnetic circular dichroism (XMCD) and polarized neutron reflectometry (PNR). We find that the out-of-plane magnetization reversal process of the MnBi:Co-Fe bilayer structure involves formation of a curling-type twisting of the magnetization in the film plane at low or intermediate reversal fields. Micromagnetic simulations are further performed to provide a detailed view of the spins at the curling center. Reminiscent of chiral spin structures known as spin bobbers, this curling in the exchange-coupled hard-soft magnetic bilayers is a new type of skyrmionic spin structure and worth further investigation

Pacific warm pool excitation, earth rotation and El Niño southern oscillations

2002-2003 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Initial Growth of Single-Crystalline Nanowires: From 3D Nucleation to 2D Growth

The initial growth stage of the single-crystalline Sb and Co nanowires with preferential orientation was studied, which were synthesized in porous anodic alumina membranes by the pulsed electrodeposition technique. It was revealed that the initial growth of the nanowires is a three-dimensional nucleation process, and then gradually transforms to two-dimensional growth via progressive nucleation mechanism, which resulting in a structure transition from polycrystalline to single crystalline. The competition among the nuclei inside the nanoscaled-confined channel and the growth kinetics is responsible for the structure transition of the initial grown nanowires

Structural and magnetic phase diagram of CeFeAsO1-xFx and its relationship to high-temperature superconductivity

We use neutron scattering to study the structural and magnetic phase transitions in the iron pnictides CeFeAsO1-xFx as the system is tuned from a semimetal to a high-transition-temperature (high-Tc) superconductor through Fluorine (F) doping x. In the undoped state, CeFeAsO develops a structural lattice distortion followed by a stripe like commensurate antiferromagnetic order with decreasing temperature. With increasing Fluorine doping, the structural phase transition decreases gradually while the antiferromagnetic order is suppressed before the appearance of superconductivity, resulting an electronic phase diagram remarkably similar to that of the high-Tc copper oxides. Comparison of the structural evolution of CeFeAsO1-xFx with other Fe-based superconductors reveals that the effective electronic band width decreases systematically for materials with higher Tc. The results suggest that electron correlation effects are important for the mechanism of high-Tc superconductivity in these Fe pnictides.Comment: 19 pages, 5 figure

Radial Growth of Qilian Juniper on the Northeast Tibetan Plateau and Potential Climate Associations

There is controversy regarding the limiting climatic factor for tree radial growth at the alpine treeline on the northeastern Tibetan Plateau. In this study, we collected 594 increment cores from 331 trees, grouped within four altitude belts spanning the range 3550 to 4020 m.a.s.l. on a single hillside. We have developed four equivalent ring-width chronologies and shown that there are no significant differences in their growth-climate responses during 1956 to 2011 or in their longer-term growth patterns during the period AD 1110–2011. The main climate influence on radial growth is shown to be precipitation variability. Missing ring analysis shows that tree radial growth at the uppermost treeline location is more sensitive to climate variation than that at other elevations, and poor tree radial growth is particularly linked to the occurrence of serious drought events. Hence water limitation, rather than temperature stress, plays the pivotal role in controlling the radial growth of Sabina przewalskii Kom. at the treeline in this region. This finding contradicts any generalisation that tree-ring chronologies from high-elevation treeline environments are mostly indicators of temperature changes

The use of nanocrystal quantum dot as fluorophore reporters in molecular beacon-based assays

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