pET-based System Research Articles

Effect of Mechanical Properties of Substrates on Flexibility of Ag Nanowire Electrodes under a Large Number of Bending Cycles

Ag nanowire electrodes have attracted considerable attention because of their potential applications in next-generation flexible electronics. However, there is a paucity of studies on the mechanical properties of Ag nanowire electrodes subjected to a large number of bending cycles. In this study, the effects of the substrate on the mechanical behavior of Ag nanowire electrodes were studied for a high bending frequency. The mechanical reliability of the Ag nanowire electrodes fabricated on a polyethylene terephthalate (PET) substrate was better than that for a polyimide (PI) substrate; the increase in the resistance of the PET-based Ag nanowire electrode was 1.07%, while that of the PI-based one was 1.23%. Nanoindentation tests showed that the elastic modulus of PI was larger than that of PET. This resulted in a lower bending strain on PET-based Ag nanowire electrodes compared to those on PI-based ones, because of the smaller distance from the neutral plane of the PET-based system. Our study showed that the mechanical properties of the substrate influenced the strain imposed on the thin layer on the substrates, which, in turn, determines the mechanical reliability of the thin-layer/substrate multilayer system.

Molecular Cloning and Chaperone Activity of DnaK from Cold-adapted Bacteria, KOPRI22215

E-mail: khlee@sejong.ac.krReceived April 6, 2011, Accepted April 21, 2011Psychrophilic bacteria have acquired cold-resistance in order to protect themselves against freezingtemperatures, which would otherwise be lethal. DnaK/DnaJ/GrpE systems are molecular chaperones whichfacilitate proper folding of newly synthesized proteins. Efficient folding processes are of great importanceespecially in a cold environment, such as the Arctic. In order to understand the protection mechanisms ofpsychrophilic bacteria against cold temperatures, we have explored a genome of KOPRI22215, tentativelyidentified as Psychromonas arctica, whose genome sequence has not yet been discovered. With an aim ofsearching for a coding gene of DnaK from KOPRI22215, we have applied a series of polymerase chainreactions (PCR) with homologous primers designed from other Psychromonas species and LA PCR in vitrocloning. 1917 bp complete coding sequence of dnaK from KOPRI22215 was identified including upstreampromoter sites. Recombinant plasmids to overexpress PaDnaK along with EcDnaK (DnaK of E. coli ) were thenconstructed in pAED4 vector and the pET-based system to induce PaDnaK expression by IPTG.Characterization assays of expressed PaDnaK were carried out by measuring survival rates upon 4 dayincubation at 4

Sensitive and Selective Photoinduced‐Electron‐Transfer‐Based Sensing of Alkylating Agents

Photoinduced-electron-transfer (PET)-based chemosensing is a very elegant way of reporting the presence of a guest species in solution. This method was successfully applied for the detection of different ionic species, such as cations, anions, and protons. Herein, we report on the application of the PET chemosensing concept for the efficient and selective detection of different alkylating agents. 2-(2-Dimethylaminoethyl)benzo[de]isoquinoline-1,3-dione (1) was found to be a highly selective and effective PET chemosensor that turns luminescent upon reacting with different alkylating agents. This PET-based system detected even rather weak alkylating agents, such as dichloromethane. A PET-based sensor that consists of 1 as the active component could detect rather low concentrations of alkylating agents in solution and in the gas phase.

Characterization ofEscherichia coliOtsA, a trehalose-6-phosphate synthase from glycosyltransferase family 20

The Ots gene cluster of Escherichia coli encodes the synthetic apparatus for the formation of alpha,alpha-1,1-trehalose, a non-reducing glucose disaccharide. The otsA gene encodes a trehalose-6-phosphate synthase, a glycosyltransferase which catalyses the synthesis of alpha,alpha-1,1-trehalose-6-phosphate from glucose-6-phosphate using a UDP-glucose donor. It has been classified into glycosyltransferase family GT-20 based upon amino-acid sequence similarities. The otsA gene has been cloned and recombinant protein overexpressed using a pET-based system in E. coli BL21 cells. The recombinant protein (MW approximately 54.7 kDa) is active and has been crystallized in two forms suitable for X-ray diffraction analysis. The first is orthorhombic, P2(1)2(1)2(1), with unit-cell parameters a = 104.1, b = 127.8, c = 179.9 A. Data for this form have been collected to 3.0 A resolution at the CLRC Daresbury Synchrotron Radiation Source. The second form has unit-cell parameters a = b = 141.9, c = 317.8 A and displays the apparent space group P4(2). These crystals diffract beyond 2 A resolution, but display merohedral twinning.