The affinity ratio--its pivotal role in gold nanoparticle-based competitive colorimetric aptasensor

We present an important role of the ratio of affinities in unmodified gold nanoparticles-based colorimetric aptasensor reactions. An affinity ratio, representing the competitive interactions among aptamers, targets, and unmodified gold nanoparticles (umAuNPs), was found to be an important factor for the sensitivity (the performance), where the affinity ratio is the affinity of the aptamer to targets divided by the affinity to umAuNPs (K(dAuNP)/K(dTarget)). In this study, the five different aptamers having different affinity ratios to both umAuNPs and targets are used, and the degree of color change is well correlated with its affinity ratio. This result is verified by using a tetracycline binding aptamer (TBA) showing different affinities to its three derivatives, tetracycline, oxytetracycline and doxycycline. Based on this model, the sensitivity of umAuNPs based colorimetric detection for ibuprofen can be enhanced simply through reducing the ibuprofen binding aptamer's affinity to umAuNP by using bis (p-sulfonatophenyl) phenylphosphine as an AuNP-capping ligand, instead of using the citrate. As a result, a clear color change is observed even at a 20-fold less amount of ibuprofen. This study presents that the performance (detection sensitivity) of umAuNPs-based colorimetric aptasensors could be improved by simply adjusting the affinity ratio of the aptamers to targets and umAuNPs, without knowing the conformational changes of aptamers upon the target binding or needing any modification of aptamer sequences.     

MOSFET-BJT hybrid mode of the gated lateral bipolar junction transistor for C-reactive protein detection

In this study, we propose a novel biosensor based on a gated lateral bipolar junction transistor (BJT) for biomaterial detection. The gated lateral BJT can function as both a BJT and a metal-oxide-semiconductor field-effect transistor (MOSFET) with both the emitter and source, and the collector and drain, coupled. C-reactive protein (CRP), which is an important disease marker in clinical examinations, can be detected using the proposed device. In the MOSFET-BJT hybrid mode, the sensitivity, selectivity, and reproducibility of the gated lateral BJT for biosensors were evaluated in this study. According to the results, in the MOSFET-BJT hybrid mode, the gated lateral BJT shows good selectivity and reproducibility. Changes in the emitter (source) current of the device for CRP antigen detection were approximately 0.65, 0.72, and 0.80 μA/decade at base currents of -50, -30, and -10 μA, respectively. The proposed device has significant application in the detection of certain biomaterials that require a dilution process using a common biosensor, such as a MOSFET-based biosensor.     

Effect of lignocellulosic inhibitory compounds on growth and ethanol fermentation of newly-isolated thermotolerant Issatchenkia orientalis

A newly isolated thermotolerant ethanologenic yeast strain, Issatchenkia orientalis IPE 100, was able to produce ethanol with a theoretical yield of 85% per g of glucose at 42 °C. Ethanol production was inhibited by furfural, hydroxymethylfurfural and vanillin concentrations above 5.56 g L⁻¹, 7.81 g L⁻¹, and 3.17 g L⁻¹, respectively, but the strain was able to produce ethanol from enzymatically hydrolyzed steam-exploded cornstalk with 93.8% of theoretical yield and 0.91 g L⁻¹ h⁻¹ of productivity at 42 °C. Therefore, I. orientalis IPE 100 is a potential candidate for commercial lignocelluloses-to-ethanol production.     

Feasibility of hydrogen production from ripened fruits by a combined two-stage (dark/dark) fermentation system

Anaerobic fermentation for hydrogen (H₂) production was studied in a two-stage fermentation system fed with different ripened fruit feedstocks (apple, pear, and grape). Among the feedstocks, ripened apple was the most efficient substrate for cumulative H₂ production (4463.7 mL-H₂ L⁻¹-culture) with a maximum H₂ yield (2.2 mol H₂ mol⁻¹ glucose) in the first stage at a hydraulic retention time (HRT) of 18 h. The additional cumulative biohydrogen (3337.4 mL-H₂ L⁻¹-culture) was produced in the second stage with the reused residual substrate from the first stage. The major byproducts in this study were butyrate, acetate, and ethanol, and butyrate was dominant among them in all test runs. During the two-stage system, the energy efficiency (H₂ conversion) obtained from mixed ripened fruits (RF) increased from 4.6% (in the first stage) to 15.5% (in the second stage), which indicated the energy efficiency can be improved by combined hydrogen production process. The RF could be used as substrates for biohydrogen fermentation in a two-stage (dark/dark) fermentation system.     

Microwave-accelerated energy-efficient esterification of free fatty acid with a heterogeneous catalyst

This paper shows energy-efficiency of microwave-accelerated esterification of free fatty acid with a heterogeneous catalyst by net microwave power measurement. In the reaction condition of 5 wt% sulfated zirconia and 1:20 M ratio of oil to methanol at 60°C and atmospheric pressure, more than 90% conversion of the esterification was achieved in 20 min by microwave heating, while it took about 130 min by conventional heating. Electric energy consumption for the microwave heating in this accelerated esterification was only 67% of estimated minimum heat energy demand because of significantly reduced reaction time.     

Isoegomaketone induces apoptosis through caspase-dependent and caspase-independent pathways in human DLD1 cells

Isoegomaketone (IK) is an essential oil component of Perilla frutescens (L.), but the mechanism by which IK induces apoptosis has never been studied. The purpose of this study was to elucidate the IK-induced apoptotic pathway in DLD1 human colon cancer cells. We observed that IK treatment over 24 h significantly inhibited cell viability in a dose-dependent manner. We also found that IK triggered cleavage of PARP. Moreover, IK treatment resulted in cleavage of caspase-8, -9, and -3 in a dose- and time-dependent manner. IK treatment also resulted in cleavage of Bid and translocation of Bax, and triggered the release of cytochrome c from the mitochondria to the cytoplasm. Furthermore, it resulted in the translocation of apoptosis inducing factor (AIF), a caspase-independent mitochondrial apoptosis factor, from the mitochondria into the nucleus. Overall, these results suggest that IK induces apoptosis through caspase-dependent and capase-independent pathways in DLD1 cells.     

Microarray expression profiling of Spodoptera litura in response to oxidative stress

To examine the expression profile of oxidative stress responsive genes in Spodoptera litura, we constructed a cDNA library from S. litura injected with hydrogen peroxide (H(2)O(2)). Using a microarray chip composed of 2,964 cDNAs, we screened gene expression at 1, 3, 5, 7, and 9 h post H(2)O(2) injection. Data were clustered into 15 groups of genes that behave similarly across each time course. Seventy-three genes were identified as being at least twofold up- or downregulated after treatment with H(2)O(2) in S. litura. We constructed expressed sequence tags (ESTs) for genes that changed at least twofold after treatment with H(2)O(2) . The functional classification of these ESTs based on Gene Ontology showed that the ESTs are rich in genes involved in oxidoreductase activity (5.7%), defense (14.3%), cellular process (22.9%), and development (17.1%).     

Chk1 and Hsp90 cooperatively regulate phosphorylation of endothelial nitric oxide synthase at serine 1179

The effects of DNA damage on NO production have not been completely elucidated. Using ultraviolet (UV) irradiation as a DNA-damaging agent, we studied its effect on NO production in bovine aortic endothelial cells (BAEC). UV irradiation acutely increased NO production, the phosphorylation of endothelial NO synthase (eNOS) at serine 1179, and eNOS activity. No alterations in eNOS expression nor phosphorylation at eNOS Thr⁴⁹⁷ or eNOS Ser¹¹⁶ were found. SB218078, a checkpoint kinase 1 (Chk1) inhibitor, inhibited UV-irradiation-stimulated eNOS-Ser¹¹⁷⁹ phosphorylation and NO production. Similarly, ectopic expression of small interference RNA for Chk1 or a dominant-negative Chk1 repressed the UV-irradiation stimulatory effect, whereas wild-type Chk1 increased basal eNOS-Ser¹¹⁷⁹ phosphorylation. Purified Chk1 directly phosphorylated eNOS Ser¹¹⁷⁹ in vitro. Confocal microscopy and coimmunoprecipitation studies revealed a colocalization of eNOS and Chk1. In basal BAEC, heat shock protein 90 (Hsp90) predominantly interacted with Chk1. This interaction, which decreased significantly in response to UV irradiation, was accompanied by increased interaction of Hsp90 with eNOS. The Hsp90 inhibitor geldanamycin attenuated UV-irradiation-stimulated eNOS-Ser¹¹⁷⁹ phosphorylation by dissociating Hsp90 from eNOS. UV irradiation and geldanamycin did not alter the interaction between eNOS and Chk1. Overall, this is the first study demonstrating that Chk1 directly phosphorylates eNOS Ser¹¹⁷⁹ in response to UV irradiation, which is dependent on Hsp90 interaction.