Search

The mycobacterial SenX3–RegX3 two-component system consists of the SenX3 sensor histidine kinase and its cognate RegX3 response regulator. This system is a phosphorelay-based regulatory system involved in sensing environmental P(i) levels and induction of genes required for P(i) acquisition under P(i)-limiting conditions. Here we demonstrate that overexpression of the kinase domain of Mycobacterium tuberculosis PknB (PknB-KD(Mtb)) inhibits the transcriptional activity of RegX3 of both M. tuberculosis and Mycobacterium smegmatis (RegX3(Mtb) and RegX3(Ms), respectively). Mass spectrometry results, along with those of in vitro phosphorylation and complementation analyses, revealed that PknB kinase activity inhibits the transcriptional activity of RegX3(Mtb) through phosphorylation events at Thr-100, Thr-191, and Thr-217. Electrophoretic mobility shift assays disclosed that phosphorylation of Thr-191 and Thr-217 abolishes the DNA-binding ability of RegX3(Mtb) and that Thr-100 phosphorylation likely prevents RegX3(Mtb) from being activated through conformational changes induced by SenX3-mediated phosphorylation. We propose that the convergence of the PknB and SenX3-RegX3 signaling pathways might enable mycobacteria to integrate environmental P(i) signals with the cellular replication state to adjust gene expression in response to P(i) availability.

Recently, aqueous method has attracted lots of attention because it enables the solution-processed metal oxide thin film with high electrical properties in low temperature fabrication condition to various flexible devices. Focusing the development of aqueous route, many researchers are only focused on metal oxide materials. However, for expansive application of the aqueous-based metal oxide films, the systematic study of performance change with process variables for the development of aqueous-based metal oxide insulator film is urgently required. Here, we propose importance of process variables to achieve high electrical-performance metal oxide insulator based on the aqueous method. We found that the significant process variables including precursor solution temperature and humidity during the spin-coating process strongly affect chemical, physical, and electrical properties of AlOx insulators. Through the optimization of significant variables in process, an AlOx insulator with a leakage current value approximately 105 times smaller and a breakdown voltage value approximately 2–3 times greater than un-optimized AlOx was realized. Finally, by introducing the optimized AlOx insulators to solution-processed InOx TFTs, we successfully achieved InOx/AlOx TFTs with remarkably high average field-effect mobility of ∼52 cm2 V−1 s−1 and on/off current ratio of 106 at fabrication temperature of 250 °C.

Perceptions of risk from nuclear power generation have received considerable attention as a significant determinant of public acceptance of nuclear power—a requirement to draw social and political support for nuclear power generation. However, the distinction between the dimensions of risk perception and the differentiated effects of such dimensions has been less explored. The present study demonstrates that two distinct dimensions of risk perception from nuclear plants—perceived intrinsic risk and extrinsic risk—reveal contrasting patterns of influence on the acceptance of nuclear power. Our results, using a sample from South Korea, show that the relative effect of perceived extrinsic risk from nuclear plants on the acceptance of nuclear power (compared to that of intrinsic risk) is stronger at higher levels of such acceptance than at lower levels. This finding provides implications for public policy to encourage the acceptance of nuclear power. Such policy should selectively choose between the two approaches—reducing the public's perceived level of intrinsic risk and that of extrinsic risk—depending on whether the policy's aims is to soften opposing voices or to promote positive voices for nuclear power.

Molybdenum cofactor (Moco), molybdopterin (MPT) complexed with molybdenum, is an essential cofactor required for the catalytic center of diverse enzymes in all domains of life. Since Moco cannot be taken up as a nutrient unlike many other cofactors, Moco requires de novo biosynthesis. During the synthesis of MPT, the sulfur atom on the C-terminus of MoaD is transferred to cyclic pyranopterin monophosphate (cPMP) which is bound in the substrate pocket of MoaE. MoaD is a ubiquitin-like (Ubl) protein and has a C-terminal di-Gly motif which is a common feature of Ubl proteins. Despite the importance of free C terminal di-Gly motif of MoaD as a sulfur carrier, some bacteria encode a fused MPT synthase in which MoaD- and MoaE-like domains are located on a single peptide. Although it has recently been reported that the fused MPT synthase MoaX from Mycobacterium tuberculosis is posttranslationally cleaved into functional MoaD and MoaE in M. smegmatis, the protease responsible for the cleavage of MoaD-MoaE fusion protein has remained unknown to date. Here we report that the JAMM/MPN+ domain containing metalloprotease DR0402 (JAMMDR) from Deinococcus radiodurans can cleave the MoaD-MoaE fusion protein DR2607, the sole MPT synthase in D. radiodurans, generating the MoaD having a C-terminal di-Gly motif. Furthermore, JAMMDR can also cleave off the MoaD from MoaD-eGFP fusion protein suggesting that JAMMDR recognizes the MoaD region rather than MoaE region in the cleaving process of MoaD-MoaE fusion protein.

PerR is a metal-dependent peroxide sensing transcription factor which controls the expression of genes involved in peroxide resistance. The function of Bacillus subtilis PerR is mainly dictated by the regulatory metal ion (Fe2+ or Mn2+) coordinated by three N-donor ligands (His37, His91, and His93) and two O-donor ligands (Asp85 and Asp104). While H2O2 sensing by PerR is mediated by Fe2+-dependent oxidation of N-donor ligand (either His37 or His91), one of the O-donor ligands (Asp104), but not Asp85, has been proposed as the key residue that regulates the sensitivity of PerR to H2O2. Here we systematically investigated the relative roles of two O-donor ligands of PerR in metal-binding affinity and H2O2 sensitivity in vivo and in vitro. Consistent with the previous report, in vitro the D104E-PerR could not sense low levels of H2O2 in the presence of excess Fe2+ sufficient for the formation of the Fe2+-bound D104E-PerR. However, the expression of PerR-regulated reporter fusion was not repressed by D104E-PerR in the presence of Fe2+, suggesting that Fe2+ is not an effective corepressor for this mutant protein in vivo. Furthermore, in vitro metal titration assays indicate that D104E-PerR has a significantly reduced affinity for Fe2+, but not for Mn2+, when compared to wild type PerR. These data indicate that the type of O-donor ligand (Asp vs. Glu) at position 104 is an important determinant in providing high Fe2+-binding affinity required for the sensing of the physiologically relevant Fe2+-levels, in addition to its role in rendering PerR highly sensitive to physiological levels of H2O2. In comparison, the D85E-PerR did not show a perturbed change in Fe2+-binding affinity, however, it displayed a slightly decreased sensitivity to H2O2 both in vivo and in vitro, suggesting that the type of O-donor ligand (Asp vs. Glu) at position 85 may be important for the fine-tuning of H2O2 sensitivity.

An insufficient sensitivity of aptamer-integrated colorimetric gold nanoparticles (AuNPs) is a common challenge in the detection of environmental chemicals. We report the use of a modified aptamer/AuNP-based sensor in conjunction with a fluorescing single-stranded DNA aptamer for the sensitive detection of bisphenol A (BPA), which is a major endocrine disruptor (EDC). While an anti-BPA single-stranded DNA aptamer was bound with BPA, a weak fluorescence signal was observed upon the addition of SYBR Green-I (SG-I), which is specific to a duplex region of the free aptamer. This reaction was accompanied by a subsequent aggregation of unmodified AuNPs (citrate-stabilized AuNPs) at high salt concentrations, leading to a color change from reddish to purple. In contrast, the absence of BPA elicited a high fluorescence signal from SG-I and produced no color change in the AuNP solution even upon the addition of salt ions. Unlike aptamers that are labeled at their ends with fluorophores, our strategy gave rise to neither a loss of target-binding affinity nor a perturbation of the AuNP colorimetry. Thus, a quantitative analysis with a broad dynamic range was achieved by combining the fluorescent and colorimetric measurements at BPA concentrations ranging over four orders of magnitude. Our approach also yielded a greater detection sensitivity (as low as 9 pg·mL−1) than classical AuNP colorimetry or other aptamer-combined methods Moreover, this method enabled the detection of BPA in a small fraction extracted from thermal paper with a high specificity among EDCs. We anticipate that this approach will facilitate further advances in the design of traditional AuNP colorimetric sensors using different aptamers for chemical sensing in the environmental and clinical fields.

Air-stable inverted polymer solar cells (IPSCs) were demonstrated by incorporating ZnO electron transport layer (ETL) fabricated with low-cost and simple brush-painting. IPSC with brush-painted ZnO using commonly used 0.75 M zinc acetate solution in 95% 2-methoxyethanol and 5% ethanolamine showed poor efficiency and reproducibility. By optimizing precursor solution and substrate temperature, thieno[3,4-b]thiophene/benzodithiophene (PTB7): [6,6]-phenyl C71-butyric acid methyl ester (PC71BM) based IPSC with high power conversion efficiency (PCE) of 7.63% and desirable device stability was achieved. This indicates that because optimized process conditions are not necessarily transferrable between different techniques, it is worthy of investigation and discussion.

This study reports a robust and straightforward approach to fabricate polymer microcapsules with a silica reinforced polyelectrolyte thin shell layer. We showed that the layer-by-layer deposition of silica nanoparticles with polyelectrolytes remarkably reinforced the shell layer, which was experimentally demonstrated by focused ion beam analysis. Moreover, we demonstrated that the molecular degradation of a model antioxidant encapsulated in our capsule system was effectively hindered during long-term storage. This indicates that the presence of the silica nanoparticles-reinforced polyelectrolyte shell layer displayed enhanced cargo retention against leakage of the antioxidant as well as oxygen attack from the surroundings.

The determinants of the public's nuclear power acceptance have received considerable attention as decisive factors regarding nuclear power policy. However, the contingency of the relative importance of different determinants has been less explored. Building on the literature of psychological distance between the individual and the object, the present study demonstrates that the relative effects of different types of perceived risks regarding nuclear power generation differ across acceptance targets. Using a sample of Korea, our results show that, regarding national acceptance of nuclear power generation, perceived risk from nuclear power plants exerts a stronger negative effect than that from radioactive waste management; however, the latter exerts a stronger negative effect than the former on local acceptance of a nuclear power plant. This finding provides implications for efficient public communication strategy to raise nuclear power acceptance.

Despite the diagnostic potential of low-molecular-weight (LMW) thiols in human diseases, their rapid and simple detection is challenging due to their reversible redox changes. Herein, we report a rapid electrokinetic detection of LMW thiols using the interaction between Bacillus subtilis-derived organic hydroperoxide resistance regulatory protein (OhrRBS) and its operator DNA element in ion concentration polarization (ICP)-coupled microfluidic multiple channels. The dimeric OhrRBS was tightly bound to the dye-labeled dsDNA element with high binding affinity (KD ≈ 4 nM) under the reduced conditions. The presence of organic hydroperoxide (OHP) and LMW thiol (X–SH) caused rapid oxidation of the reduced Cys residue (OhrRBS–SH) of the protein into the sulfenic acid form (OhrRBS–SOH) by OHP and subsequently into the disulfide form (OhrRBS–S–S–X) by LMW thiol via S-thiolation, leading to a rapid release of OhrRBS from the fluorescent dsDNA element. Based on this principle, the fluorescence zones of the dsDNA-protein complex in response to LMW thiols were rapidly separated in the microfluidic channels by electrokinetic mobility. Owing to the ability of ICP-coupled microfluidics to concentrate charged samples, this electrokinetic method enabled the rapid determination ( 2 μM) of LMW thiols, depending on their molecular weights and concentrations. Additionally, this strategy enabled the simultaneous detection of free and total LMW thiols in mouse serum. These results suggest that the ICP-coupled microfluidic platform in combination with the OhrRBS–DNA complex will be useful for monitoring rapid redox changes of LMW thiols in real samples.

To demonstrate fully brush-painted planar heterojunction perovskite solar cells (PeSCs), poly (3,4-ethylendioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) hole transport layer (HTL), CH3NH3PbI3 perovskite photoactive layer, and [6,6]-phenyl C61-butyric acid methyl ester (PCBM) electron acceptor layer are successively brush-painted. In particular, correlation between morphology of perovskites and overall performance of PeSCs are investigated depending on the perovskites precursor. Devices with brush-painted perovskite using generally used N,N-dimethylformamide (DMF) solvent show poor performance and large deviation in cell-performance. However, PeSCs with brush-painted perovskite employing protic 2-Methoxyethanol (2-M) as DMF-alternative solvent exhibit comparable power conversion efficiency (PCE) of 9.08% to conventional spin-coated device and excellent reproducibility in device performance is observed as well. Furthermore, a fully brush-painted PeSC based on flexible substrates, showing PCE of 7.75%, is successfully demonstrated.

MoS2 counter electrodes obtained via spin-coating of MoS2 nanosheets followed by thermal treatment at varied temperatures were used as highly transparent counter electrodes in dye-sensitized solar cells, and the effect of temperatures on electrocatalytic activity as well as overall power conversion efficiency (PCE) of DSSCs was investigated. DSSC with thermally treated MoS2 at 100 °C exhibited comparable PCE of 7.35% to conventional Pt contained DSSC showing 7.53%, whereas cell performance with MoS2 thermally treated at higher temperature over 300 °C showed significant decrease in PCE due to the chemical change of MoS2 to poor electrocatalytic MoO3.

In many Gram-positive bacteria PerR is a major peroxide sensor whose repressor activity is dependent on a bound metal cofactor. The prototype for PerR sensors, the Bacillus subtilis PerRBS protein, represses target genes when bound to either Mn(2+) or Fe(2+) as corepressor, but only the Fe(2+)-bound form responds to H2O2. The orthologous protein in the human pathogen Staphylococcus aureus, PerRSA, plays important roles in H2O2 resistance and virulence. However, PerRSA is reported to only respond to Mn(2+) as corepressor, which suggests that it might rely on a distinct, iron-independent mechanism for H2O2 sensing. Here we demonstrate that PerRSA uses either Fe(2+) or Mn(2+) as corepressor, and that, like PerRBS, the Fe(2+)-bound form of PerRSA senses physiological levels of H2O2 by iron-mediated histidine oxidation. Moreover, we show that PerRSA is poised to sense very low levels of endogenous H2O2, which normally cannot be sensed by B. subtilis PerRBS. This hypersensitivity of PerRSA accounts for the apparent lack of Fe(2+)-dependent repressor activity and consequent Mn(2+)-specific repressor activity under aerobic conditions. We also provide evidence that the activity of PerRSA is directly correlated with virulence, whereas it is inversely correlated with H2O2 resistance, suggesting that PerRSA may be an attractive target for the control of S. aureus pathogenesis.

A microbial fuel cell (MFC) is a bio-electrochemical system that drives a current by mimicking bacterial interactions found in nature. Usually, MFCs use Nafion as a PEM to separate the electrodes while permitting protons transfer between the anode and cathode. However, Nafion is expensive and accounts for a large percentage of the costs in MFC configuration. Here, we show MFCs using hydrocarbon-based PEM, disulfonated poly (arylene ether sulfone) (BPSH), which is considered as one of alternative PEM, and relatively inexpensive as compared with Nafion. BPSH membranes exhibit a comparable performance to Nafion 212. Especially, BPSH 40 and 60 (mole %) have higher proton conductivity than Nafion 212. In a two-chamber system, MFC with BPSH 40 shows higher voltage than that with Nafion 212. MFCs with BPSH 20 and 30 show lower voltage decline than other PEMs. In a single-chamber system, a voltage of MFC with BPSH 40 shows about 30% higher (17 mV) than that with Nafion 212 (13 mV) with internal resistance of 10 Ω. In addition, The MFC with BPSH 40 produced about 10% higher maximum power density (126 mW m−2) than that with Nafion 212 (111 mW m−2).

For the identification of irradiated food, current analysis methods have limitations regarding presence and stability of radiation-induced markers. In this study, different spice blends with small quantity of different irradiated (0, 1 and 10 kGy) spice powders, such as red pepper, garlic or ginger, were investigated using PSL and TL techniques. In PSL-based screening analysis, the spice blends containing 10% of irradiated materials (1 or 10 kGy) were determined as intermediate or positive. In TL results, the blends containing 1% of 1 or 10 kGy-irradiated spices showed the typical TL glow curves that could be interpreted as positive. The blends with irradiated garlic powder provided more good results where identification was possible at 0.5% mixing of irradiated sample. However, the TL ratios of all spice blends were

Buforin IIb is a novel cell-penetrating anticancer peptide derived from histone H2A. In this study, we enhanced the cancer targeting specificity of buforin IIb using a tumor-associated enzyme-controlled activation strategy. Buforin IIb was fused with an anionic peptide (modified magainin intervening sequence, MMIS), which neutralizes the positive charge of buforin IIb and thus renders it inactive, via a matrix metalloproteinases (MMPs)-cleavable linker. The resulting MMIS:buforin IIb fusion peptide was completely inactive against MMPs-nonproducing cells. However, when the fusion peptide was administrated to MMPs-producing cancer cells, it regained the killing activity by releasing free buforin IIb through MMPs-mediated cleavage. Moreover, the activity of the fusion peptide toward MMPs-producing cancer cells was significantly decreased when the cells were pretreated with a MMP inhibitor. Taken together, these data indicate that the cancer targeting specificity of MMIS:buforin IIb is enhanced compared to the parent peptide by reactivation at the specialized areas where MMPs are pathologically produced.

In Bacillus subtilis most peroxide-inducible oxidative stress genes are regulated by a metal-dependent repressor, PerR. PerR is a dimeric, Zn2+-containing metalloprotein with a regulatory metal-binding site that binds Fe2+ (PerR:Zn,Fe) or Mn2+ (PerR: Zn,Mn). Reaction of PerR:Zn,Fe with low levels of hydrogen peroxide (H2O2) leads to oxidation of two His residues thereby leading to derepression. When bound to Mn2+, the resulting PerR:Zn,Mn is much less sensitive to oxidative inactivation. Here we demonstrate that the structural Zn2+ is coordinated in a highly stable, intrasubunit Cys4:Zn2+ site. Oxidation of this Cys4:Zn2+ site by H2O2 leads to the formation of intrasubunit disulfide bonds. The rate of oxidation is too slow to account for induction of the peroxide stress response by micromolar levels of H2O2 but could contribute to induction under severe oxidative stress conditions. In vivo studies demonstrated that inactivation of PerR:Zn,Mn required 10 mm H2O2, a level at least 1000 times greater than that needed for inactivation of PerR:Zn,Fe. Surprisingly even under these severe oxidation conditions there was little if any detectable oxidation of cysteine residues in vivo: derepression was correlated with oxidation of the regulatory site. Because oxidation at this site required bound Fe2+ in vitro, we suggest that treatment of cells with 10 mm H2O2 released sufficient Fe2+ into the cytosol to effect a transition of PerR from the PerR:Zn,Mn form to the peroxide-sensitive PerR: Zn,Fe form. This model is supported by metal ion affinity measurements demonstrating that PerR bound Fe2+ with higher affinity than Mn2+.

A sodF gene coding for iron- and zinc-containing superoxide dismutase (FeZnSOD) of Streptomyces griseus was cloned and sequenced. A 5' end of 0.8-kb sodF transcript was mapped at the 57 nucleotides upstream from an ATG initiation codon. Employing expressions of sodF::xylE fusions in trans in Streptomyces lividans, nickel-responsive transcriptional repression was found to be relieved if mutations were introduced into an operator sequence of inverted-repeat, TTGCAN(7)TGCAA, which traverses the 5' end (+1, G) of the sodF mRNA. Nickel-dependent interaction between cell extracts and sodF regulatory DNA, monitored through gel-mobility shift assay, was abolished when the operator was mutated. Recombinant sodF operon having operator mutations showed protein level and enzyme activity, which were no longer repressed by nickel, suggesting that nickel-responsive repression of FeZnSOD is regulated mainly at the level of transcription through the operator.

In order to estimate more exactly the performance of wire-plate electrostatic precipitators (ESP), a new computational scheme has been developed, where the involved physical phenomena such as corona-field, turbulent electrohydrodynamic (EHD) flow field, in situ particle charging and turbulent motion of particles are treated simultaneously. To overcome the deficiencies of the Eulerian method used up to now, a Lagrangian particle-tracking method coupled with the Monte-Carlo method for simulating the stochastic nature of turbulence is used. The scheme is applied to the analysis of an experimental wire-plate ESP of short length (Kihm, Ph.D. thesis, Stanford University, Stanford, 1987), where the effect of developing flow in the entrance region is substantial. The simulation results for two different flow conditions of high and low turbulent intensity at the inlet clearly reproduced the steeper increase of efficiency with voltage for low turbulence case observed in the experiment, and also the efficiency values agree very well with the experimental data for one particle size of 4 μm.

Two unique isozymes of superoxide dismutase (EC 1.15.1.1) were purified to apparent homogeneity from Streptomyces griseus by a purification procedure consisting of ammonium sulfate precipitation and chromatographies on DEAE Sephacel, Sephacryl S-200, and DEAE 5PW. Superoxide dismutase I was composed of four identical subunits of 13.0 kDa. The absorption spectrum of superoxide dismutase I exhibited absorption bands at 276 and 378 nm and a broad shoulder at 530 nm. The g values of electron paramagnetic resonance spectrum of superoxide dismutase I were g1 = 2.304, g2 = 2.248, and g3 = 2.012 and the resonance centered at g3 = 2.012 was split into triplet, indicating nickel-containing superoxide dismutase. Superoxide dismutase I contained 0.89 g-atom of nickel per mole of 13.0-kDa subunit. Superoxide dismutase II was composed of four identical subunits of 22.0 kDa. The absorption spectrum of superoxide dismutase II showed the featureless absorption band in the range of 300-500 nm. The g values of electron paramagnetic resonance spectrum of superoxide dismutase II were gz = 4.762, gx = 4.072, and gy = 3.742, indicating iron-containing superoxide dismutase. Superoxide dismutase II uniquely contains 0.40 g-atom of iron per mole of monomer as well as 0.43 g-atom of zinc per mole of monomer. The immunological cross-reactivity between two isozymes was not found. Nickel-containing superoxide dismutase was widely distributed within the genus Streptomyces; however, iron- and zinc-containing superoxide dismutase was not found in S. albus and S. longisporoflavus, on the basis of the immunological cross-reactivity.

A control method which drives the permanent magnet A.C. servo motor without the detection of the rotor position by the absolute position transducer such as an absolute encoder or a resolver is described. Only an incremental encoder is coupled to the motor shaft in order to obtain information about electrical commutation, motor speed, and motor position. A fuzzy algorithm is developed in order to estimate the absolute rotor position which is essential to electrical commutation. The center of gravity method defuzzifies the output variables of the fuzzy rules to generate the current command for estimation. A pulse interval measurement method is discussed, which enables the measurement of the motor speed and the motor position with the same resolution from a standstill to the rated speed. A digital current control method is proposed, which makes the permanent magnet A.C. servo motor fed by impressed currents. The entire control algorithm is implemented on the control system consisting of a digital signal processor (DSP) ADSP2101. Experimental results show that the proposed control scheme can be effectively used in controlling the permanent magnet A.C. servo motor with only an incremental encoder as a position transducer with high dynamic performance.