Development and characterization of a magnetic bead-quantum dot nanoparticles based assay capable of Escherichia coli O157:H7 quantification

The development and characterization of a magnetic bead (MB)-quantum dot (QD) nanoparticles based assay capable of quantifying pathogenic bacteria is presented here. The MB-QD assay operates by having a capturing probe DNA selectively linked to the signaling probe DNA via the target genomic DNA (gDNA) during DNA hybridization. The signaling probe DNA is labeled with fluorescent QD₅₆₅ which serves as a reporter. The capturing probe DNA is conjugated simultaneously to a MB and another QD₆₅₅, which serve as a carrier and an internal standard, respectively. Successfully captured target gDNA is separated using a magnetic field and is quantified via a spectrofluorometer. The use of QDs (i.e., QD₅₆₅/QD₆₅₅) as both a fluorescence label and an internal standard increased the sensitivity of the assay. The passivation effect and the molar ratio between QD and DNA were optimized. The MB-QD assay demonstrated a detection limit of 890 zeptomolar (i.e., 10⁻²¹ mol L⁻¹) concentration for the linear single stranded DNA (ssDNA). It also demonstrated a detection limit of 87 gene copies for double stranded DNA (dsDNA) eaeA gene extracted from pure Escherichia coli (E. coli) O157:H7 culture. Its corresponding dynamic range, sensitivity, and selectivity were also presented. Finally, the bacterial gDNA of E. coli O157:H7 was used to highlight the MB-QD assay's ability to detect below the minimum infective dose (i.e., 100 organisms) of E. coli O157:H7 in water environment.     

茄黄斑螟性信息素化学的结构签定(英文)

本文采用TLC、GC、微量臭氧化和GC-MS等分析方法,从茄黄斑螟雌蛾性腺体提取物中,分离和鉴定出性信息素反-11-十六碳烯醇乙酸酯(1a)。触角电位和田间试验证明,天然提取物和合成样品均有强烈的生物活性。     

Biologisch aktive 3,3-Dimethylbicyclo[2.2.2]octane: Synthesen in der Isocamphanreihe, 35. Mitt.

Summary The bicyclo[2.2.1]- and [2.2.2]-systems are part of numerous biological active substances. Continuing our syntheses in the isocamphane series the homologous isocamphanes of mecamylamine (1 a) and of the fungicidal bicyclic compound2 were synthesized. Furthermore the syntheses ofE-homoisosantalene (15) andE,E-homoisosantalol (16) are described.

     

Tandem cross metathesis and intramolecular aza-Michael reaction to synthesize bicyclic piperidines and indolizidine 167E

We have successfully transformed the terminal alkenes of dihydropyridones to the α,β-unsaturated esters by cross metathesis (CM). After detosylation the secondary amides can undergo the intramolecular aza-Michael reaction to give the bicyclic piperidine structures. The stereoselectivity of the aza-Michael reaction is determined by the size of the newly formed ring. With simple transformations we have also achieved the synthesis of indolizidine 167E.     

High power impulse magnetron sputtering (HIPIMS) and traditional pulsed sputtering (DCMSP) Ag-surfaces leading to E. coli inactivation

This study addresses the high power impulse magnetron sputtering (HIPIMS) deposition of Ag-nanoparticle films on polyester and the comparison with films deposited by direct current pulsed magnetron sputtering (DCMSP). The first evidence is presented for the Escherichia coli bacterial inactivation by HIPIMS sputtered polyester compared to Ag-polyester sputtered by DCMSP. HIPIMS layers were significantly thinner than the DCMSP sputtered layers needing a much lower Ag-loading to inactivate E. coli within the same time scale. The Ag-nanoparticle films sputtered by DCMSP at 300 mA for 160 s was observed to inactivate completely E. coli within 2 h having a content of 0.205% Ag wt%/polyester wt%. HIPIMS-sputtered at 5 A for 75 s led to complete E. coli bacterial inactivation also within 2 h having a content Ag 0.031% Ag wt%/polyester wt%. The atomic rate of deposition with DCMSP is 6.2 × 10¹⁵ atoms Ag/cm² s while with HPIMS this rate was 2.7 × 10¹⁵ atoms Ag/cm² s. The degree of ionization of Ag⁺/Ag²⁺ and Ar⁺/Ar²⁺ was proportional to the target current applied during HIPIMS-sputtering as determined by mass spectroscopy. These experiments reveal significant differences at the higher end of the currents applied during HIPIMS sputtering as illustrated by the ion-flux composition. X-ray photoelectron spectroscopy (XPS) was used to determine the surface atomic concentration of O, Ag, and C on the Ag-polyester. These surface atomic concentrations were followed during the E. coli inactivation time providing the evidence for the E. coli oxidation on the Ag-polyester. X-ray diffraction shows Ag-metallic character for DCMSP sputtered samples for longer times compared to the Ag-clusters sputtered by HIPIMS leading to Ag-clusters aggregates. Ag-nanoparticle films on polyester sputtered by HIPIMS contain less Ag and are thinner compared to Ag-nanoparticle films sputtered by DCMSP.     

Concise Synthesis of (3Z)-Dodecen-12-olide,Pheromone Component of the Emerald Ash Borer

Emerald ash borer (EAB), Agrilus planipennis Fairmaire, is an invasive insect that has killed millions of ash trees in Canada and the USA. (3Z)-Dodecen-12-olide is a known female-produced pheromone of this insect, and a concise, three-step synthesis of a 2:1 blend of (3Z)-dodecen-12-olide and (3E)-dodecen-12-olide starting from commercially available (2-carboxyethyl)triphenylphosphonium bromide and 10-bromo-1-decene is described. The key steps in this synthesis are a lithium-salt-free Wittig reaction and an intramolecular S_N2 esterification. Both of these macrocyclic lactones are behaviorally active toward EAB, and the 2:1 blend whose synthesis is described here has the potential to be a detection agent, mating disruptor, or mass trapping agent, which could be used in the control of EAB.     

气相色谱法测定化妆品中的 VE 含量

介绍了一种用气相色谱法准确快速测定品中ＶＥ２含量的新方法。该法以ＶＣ作保护剂,用环已烷提取样品,ＳＥＰ－ＰＡＫ ＡＬＵＭ－Ａ小柱净化。以氯氰菊酯内标物,在１？５％ＯＶ＝－１７色谱柱上进行分离,测定化妆口中ＶＥ含量。内标物与样品的分离度为１．５５。平均回收纺为９４．３％～９８．８％,相对标准偏差为１．７％～３．５％（ｎ＝５）。