Fluorescence quenching and measurement of captopril in pharmaceuticals

The mechanism of fluorescence quenching of the product S in the presence of captopril was studied. The maximum emission wavelength of the product S was at 405 nm with the excitation wavelength at 316 nm. It was found that the fluorescence quenching of product S was of a static one and the binding constant (K) was 9.29 × 106 J mol-1. A linear relationship was found between the relative fluorescence intensity of the product S-captopril system and the concentration of captopril. Under optimum conditions, the linear range of the calibration curve for captopril was 2~160 μg L-1 with a correlation coefficient of 0.9926 and a detection limit of 0.1 μg L-1. The relative standard deviation (RSD) was 3.60%. The analytical results of the pharmaceuticals obtained by this novel method agreed quite well with those obtained by the KIO3 titrimetry

Fluorescence quenching and measurement of captopril in pharmaceuticals

270-276The mechanism of fluorescence quenching of the product S in the presence of captopril was studied. The maximum emission wavelength of the product S was at 405 nm with the excitation wavelength at 316 nm. It was found that the fluorescence quenching of product S was of a static one and the binding constant (K) was 9.29 × 106 J mol-1. A linear relationship was found between the relative fluorescence intensity of the product S-captopril system and the concentration of captopril. Under optimum conditions, the linear range of the calibration curve for captopril was 2~160 μg L-1 with a correlation coefficient of 0.9926 and a detection limit of 0.1 μg L-1. The relative standard deviation (RSD) was 3.60%. The analytical results of the pharmaceuticals obtained by this novel method agreed quite well with those obtained by the KIO3 titrimetry

A Facile Synthesis and Optical Properties of Bundle-Shaped TbPO 4

Bundle-shaped TbPO4·H2O nanorods have been prepared by a facile hydrothermal technique and characterized by XRD, SEM, TEM, UV-Vis diffuse reflectance spectrum (DRS), photoluminescence (PL) spectrum, and lifetime. The results indicate that the obtained sample has hexagonal structure of TbPO4·H2O and is composed of nanorods bundles which is assembled from many single crystalline nanorods with the diameter of around 45 nm and the length of 2.3 μm. The growth of the single crystalline nanorod is along the (001) plane direction. Under the UV light irradiation, TbPO4·H2O nanorods bundles exhibit bright green emission corresponding to the D54→F7J (J=6,5,4,3) transitions of the Tb3+ ions, and the lifetime is determined to be about 0.24 ms

bifA Regulates Biofilm Development of Pseudomonas putida MnB1 as a Primary Response to H2O2 and Mn2+

Pseudomonas putida (P. putida) MnB1 is a widely used model strain in environment science and technology for determining microbial manganese oxidation. Numerous studies have demonstrated that the growth and metabolism of P. putida MnB1 are influenced by various environmental factors. In this study, we investigated the effects of hydrogen peroxide (H2O2) and manganese (Mn2+) on proliferation, Mn2+ acquisition, anti-oxidative system, and biofilm formation of P. putida MnB1. The related orthologs of 4 genes, mco, mntABC, sod, and bifA, were amplified from P. putida GB1 and their involvement were assayed, respectively. We found that P. putida MnB1 degraded H2O2, and quickly recovered for proliferation, but its intracellular oxidative stress state was maintained, with rapid biofilm formation after H2O2 depletion. The data from mco, mntABC, sod and bifA expression levels by qRT-PCR, elucidated a sensitivity toward bifA-mediated biofilm formation, in contrary to intracellular anti-oxidative system under H2O2 exposure. Meanwhile, Mn2+ ion supply inhibited biofilm formation of P. putida MnB1. The expression pattern of these genes showed that Mn2+ ion supply likely functioned to modulate biofilm formation rather than only acting as nutrient substrate for P. putida MnB1. Furthermore, blockade of BifA activity by GTP increased the formation and development of biofilms during H2O2 exposure, while converse response to Mn2+ ion supply was evident. These distinct cellular responses to H2O2 and Mn2+ provide insights on the common mechanism by which environmental microorganisms may be protected from exogenous factors. We postulate that BifA-mediated biofilm formation but not intracellular anti-oxidative system may be a primary protective strategy adopted by P. putida MnB1. These findings will highlight the understanding of microbial adaptation mechanisms to distinct environmental stresses

Mediation of Extracellular Polymeric Substances in Microbial Reduction of Hematite by Shewanella oneidensis MR-1

Extracellular electron transfer (EET) plays a fundamental role in microbial reduction/oxidation of minerals. Extracellular polymeric substances (EPS) surrounding the cells constitute a matrix that separates the cell’s outer membrane from insoluble minerals and environmental fluid. This study investigated the effects of EPS on EET processes during microbial reduction of hematite by the iron-reducing strain Shewanella oneidensis MR-1 (MR-1). Electrochemical characterization techniques were employed to determine the influence of EPS components on the redox ability of MR-1. Cells with removed EPS exhibited approximately 30% higher hematite reduction than regular MR-1 cells, and produced a current density of 56 μA cm-2, corresponding to 3–4 fold that of regular MR-1. The superior EET of EPS-deprived cells could be attributed to direct contact between outer membrane proteins and hematite surface, as indicated by more redox peaks being detected by cyclic voltammetry and differential pulse voltammetry. The significantly reduced current density of MR-1 cells treated with proteinase K and deoxyribonuclease suggests that the electron transfer capacity across the EPS layer depends mainly on the spatial distribution of specific proteins and electron shuttles. Exopolysaccharides in EPS tend to inhibit electron transfer, however they also favor the attachment of cells onto hematite surfaces. Consistently, the charge transfer resistance of cells lacking EPS was only 116.3 Ω, approximately 44 times lower than that of regular cells (5,139.1 Ω). These findings point to a negative influence of EPS on EET processes for microbial reduction/oxidation of minerals

Genome-wide analysis of circular RNAs in goat skin fibroblast cells in response to Orf virus infection

Orf, caused by Orf virus (ORFV), is a globally distributed zoonotic disease responsible for serious economic losses in the agricultural sector. However, the mechanism underlying ORFV infection remains largely unknown. Circular RNAs (circRNAs), a novel type of endogenous non-coding RNAs, play important roles in various pathological processes but their involvement in ORFV infection and host response is unclear. In the current study, whole transcriptome sequencing and small RNA sequencing were performed in ORFV-infected goat skin fibroblast cells and uninfected cells. A total of 151 circRNAs, 341 messenger RNAs (mRNAs), and 56 microRNAs (miRNAs) were differently expressed following ORFV infection. Four circRNAs: circRNA1001, circRNA1684, circRNA3127 and circRNA7880 were validated by qRT-PCR and Sanger sequencing. Gene ontology (GO) analysis indicated that host genes of differently expressed circRNAs were significantly enriched in regulation of inflammatory response, epithelial structure maintenance, positive regulation of cell migration, positive regulation of ubiquitin-protein transferase activity, regulation of ion transmembrane transport, etc. The constructed circRNA-miRNA-mRNA network suggested that circRNAs may function as miRNA sponges indirectly regulating gene expression following ORFV infection. Our study presented the first comprehensive profiles of circRNAs in response to ORFV infection, thus providing new clues for the mechanisms of interactions between ORFV and the host

Phylogenetic distribution of the capsid assembly protein gene (g20) of cyanophages in paddy floodwaters in Northeast China.

Numerous studies have revealed the high diversity of cyanophages in marine and freshwater environments, but little is currently known about the diversity of cyanophages in paddy fields, particularly in Northeast (NE) China. To elucidate the genetic diversity of cyanophages in paddy floodwaters in NE China, viral capsid assembly protein gene (g20) sequences from five floodwater samples were amplified with the primers CPS1 and CPS8. Denaturing gradient gel electrophoresis (DGGE) was applied to distinguish different g20 clones. In total, 54 clones differing in g20 nucleotide sequences were obtained in this study. Phylogenetic analysis showed that the distribution of g20 sequences in this study was different from that in Japanese paddy fields, and all the sequences were grouped into Clusters α, β, γ and ε. Within Clusters α and β, three new small clusters (PFW-VII∼-IX) were identified. UniFrac analysis of g20 clone assemblages demonstrated that the community compositions of cyanophage varied among marine, lake and paddy field environments. In paddy floodwater, community compositions of cyanophage were also different between NE China and Japan

Mechanical response of the sealing packer based on two rubber materials at high temperatures

The compression packer is an important downhole oil production tool, and its failure is mainly attributed to the degradation of its embedded rubber cylinders under the action of high temperatures. In the present study we have made a comprehensive investigation on the mechanical response of the sealing packer based on two rubber materials at high temperatures. Firstly, by measuring the material parameters under different temperatures, we established the constitutive relationships of the two rubber materials (Aflas and Kalrez) in consideration of the temperature effect, in the light of the Mooney-Rivlin model. Next, the sealing performances of two optimized packers were analyzed including Aflas and Kalrez rubber cylinders. The effects of high temperature and the initial setting pressure on the sealing effects of these two optimized packers were probed based on the finite element analysis (FEA), and the ranges of temperature and initial setting pressure for best sealing were determined. This study can provide some ideas for the material selection and structural optimization for sealing packers, aiming to ensure the safe operation of the packers in severe environments