Effects of crossed states on photoluminescence excitation spectroscopy of InAs quantum dots

In this report, the influence of the intrinsic transitions between bound-to-delocalized states (crossed states or quasicontinuous density of electron-hole states) on photoluminescence excitation (PLE) spectra of InAs quantum dots (QDs) was investigated. The InAs QDs were different in size, shape, and number of bound states. Results from the PLE spectroscopy at low temperature and under a high magnetic field (up to 14 T) were compared. Our findings show that the profile of the PLE resonances associated with the bound transitions disintegrated and broadened. This was attributed to the coupling of the localized QD excited states to the crossed states and scattering of longitudinal acoustical (LA) phonons. The degree of spectral linewidth broadening was larger for the excited state in smaller QDs because of the higher crossed joint density of states and scattering rate

Characterization of infrared chemical sensors modified with ZnO nanowires for the detection of volatile organic compounds

In this paper we describe the application and characterization of zinc oxide (ZnO) nanowires in an infrared (IR) chemical sensing system for the detection of volatile organic compounds (VOCs). Under suitable conditions, we grew ZnO nanowires on the surfaces of IR internal reflection elements (IREs) and obtained successful results for the detection of VOCs. ZnO nanowires offer a large surface area to effectively adsorb the examined species; the sensitivity of these IR sensing systems was increased by 3- to 15-fold after surface treatment with the ZnO nanowires. To explore the performance of this type of sensor, we correlated the morphologies of the ZnO nanowires grown on the surfaces of the IREs with the adsorption behavior observed during the sensing of the VOCs. To characterize the properties of the ZnO nanowires during the detection of VOCs having a range of functionalities, we classified the VOCs and examined their enrichment factors by comparing the IR signals detected in the presence and absence of the ZnO nanowires. Our results indicate that the ZnO nanowires exhibited better performance for the detection of aromatic-type VOCs than they did for non-aromatic compounds. For quantitative analyses, we examined several compounds for their responses toward varying quantities of injected VOCs. Our results indicate that the IREs treated with ZnO nanowires display acceptable linearity in their standard curves; the linear regression coefficients were higher than 0.995 for a range of volatile compounds

Avian reovirus S1133-induced DNA damage signaling and subsequent apoptosis in cultured cells and in chickens

In this study, intracellular signaling in ARV S1133-mediated apoptosis was investigated. A microarray was used to examine the gene expression profiles of cells upon ARV S1133 infection and ARV-encoded pro-apoptotic protein sigma C overexpression. The analysis indicated that in the set of DNA-damage-responsive genes, DDIT-3 and GADD45 alpha were both upregulated by viral infection and sigma C overexpression. Further investigation demonstrated that both treatments caused DNA breaks, which increased the expression and/or phosphorylation of DNA damage response proteins. ROS and lipid peroxidation levels were increased, and ARV S1133 and sigma C caused apoptosis mediated by DNA damage signaling. ROS scavenger NAC, caffeine and an ATM-specific inhibitor significantly reduced ARV S1133- and sigma C-induced DNA breaks, DDIT-3 and GADD45 alpha expression, H2AX phosphorylation, and apoptosis. Overexpression of DDIT-3 and GADD45 alpha enhanced the oxidative stress and apoptosis induced by ARV S1133 and sigma C. In conclusion, our results demonstrate the involvement of the DNA-damage-signaling pathway in ARV S1133- and sigma C-induced apoptosis

Cucurbitane Triterpenoids from Momordica charantia and Their Cytoprotective Activity in tert-Butyl Hydroperoxide-Induced Hepatotoxicity of HepG2 Cells

Two novel pentanorcucurbitane triterpenes, 22-hydroxy-23,24,25,26,27-pentanorcucurbit-5-en-3-one (1) and 3,7-dioxo-23,24,25,26,27-pentanorcucurbit-5-en-22-mc acid (2) together with a new trinorcucurbitane triterpene, 25,26,27-trinorcucurbit-5-ene-3,7,23-trione (3) were isolated from the methyl alcohol extract of the stems of Momordica charantia. The structures of the new compounds were elucidated by spectroscopic methods. Compounds 2 and 3 showed potent cytoprotective activity in tert-butyl hydroperoxide (t-BHP)-induced hepatotoxicity of HepG2 cells

Development and characterization of monoclonal antibodies against avian reovirus sigma C protein and their application in detection of avian reovirus isolates

Avian reovirus (ARV) is a non-enveloped virus with a segmented double-stranded RNA genome surrounded by a double icosahedral capsid shell. ARVs are associated with viral arthritis, immunosuppression, and enteric diseases in poultry. The sigma C protein was involved in induction of apoptosis and neutralization antibody. In the present study, sigma C-His protein was expressed in Sf9 insect cells and purified by immobilized metal affinity chromatography. Eight monoclonal antibodies (mAbs) against sigma C-His and three mAbs against His were screened from hybridoma cells produced by fusion of splenocytes from immunized mice with NS1 myeloma cells. Among the eight mAbs against sigma C protein, all belonged to the IgG isotype except three for IgM. It was discovered that all anti-His mAbs were mixtures of IgG and IgM isotypes. mAbs reacted with sigma C-His protein in a conformation-independent manner based on dot blot and western blotting assays. The competitive binding assay indicated that all mAbs recognized the same epitope on sigma C protein that was conserved in different isolates. Compared with the commercial anti-ARV S1133 polyclonal antibody, mAb (D15) had universal reactivity to all serotypes or genotypes of ARVs tested. This monoclonal antibody may therefore be useful for the development of an antigen-capture enzyme-linked immunosorbent assay for rapid detection of field isolates

Deciphering the roles of fatty acids and oils in fungichromin enhancement from Streptomyces padanus

Fungichromin (FC), a polyene macrolide antibiotic, was found to be useful in the treatment of resistance for plant diseases such as Rhizoctonia damping-off of cabbage and tomato late blight. A novel strain, Streptomyces padanus PMS-702, was employed to study the cultivation conditions for FC production. When using linoleic acid as an additive, a negative effect on FC production was observed. On the contrary, when using oleic acid in concentration of 0.01 M (2.82 g/L), a 3.5-fold enhancement of FC production with a slight increase in cell biomass was obtained. To study the effects of plant oils, various plant oils were used as additives. It was found that all the plant oils (namely, corn oil, olive oil and etc.) promote FC production up to about 4.9-fold as compared to that without such an addition. A quantitative analysis on FC yield indicated that, at a lower concentration, fatty acids and plant oils play roles as both a stimulator and a carbon source whereas, at a higher concentration, they serve mainly as the carbon source. This morphological study showed that the addition of fatty acids and oils in the medium vary the cell membrane permeability. The fact that FC could be rapidly secreted out into the medium after its synthesis as well as its stimulatory effect attributed to a dramatic increase in FC production. (C) 2010 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved

BMP-regulated exosomes from Drosophila male reproductive glands reprogram female behavior

Male reproductive glands secrete signals into seminal fluid to facilitate reproductive success. In Drosophila melanogaster, these signals are generated by a variety of seminal peptides, many produced by the accessory glands (AGs). One epithelial cell type in the adult male AGs, the secondary cell (SC), grows selectively in response to bone morphogenetic protein (BMP) signaling. This signaling is involved in blocking the rapid remating of mated females, which contributes to the reproductive advantage of the first male to mate. In this paper, we show that SCs secrete exosomes, membrane-bound vesicles generated inside late endosomal multivesicular bodies (MVBs). After mating, exosomes fuse with sperm (as also seen in vitro for human prostate-derived exosomes and sperm) and interact with female reproductive tract epithelia. Exosome release was required to inhibit female remating behavior, suggesting that exosomes are downstream effectors of BMP signaling. Indeed, when BMP signaling was reduced in SCs, vesicles were still formed in MVBs but not secreted as exosomes. These results demonstrate a new function for the MVB–exosome pathway in the reproductive tract that appears to be conserved across evolution.</jats:p