Addition of difluoromethyl radicals to glycals: a new route to alpha-CF2-D-glycosides

The synthesis of synthetically useful alpha-CF2-glycosides by radical addition of ethyl bromodifluoroacetate onto 2-benzyloxyglycals is described. The methodology provides an access to alpha-O-glycoside mimics and, potentially, to valuable alpha-O-glycoconjugate analogues.     

The Catalytic Mechanism of Human Parainfluenza Virus Type 3 Haemagglutinin‐Neuraminidase Revealed

Human parainfluenza virus type 3 (hPIV‐3) is one of the leading causes for lower respiratory tract disease in children, with neither an approved antiviral drug nor vaccine available to date. Understanding the catalytic mechanism of human parainfluenza virus haemagglutinin‐neuraminidase (HN) protein is key to the design of specific inhibitors against this virus. Herein, we used ¹H NMR spectroscopy, X‐ray crystallography, and virological assays to study the catalytic mechanism of the HN enzyme activity and have identified the conserved Tyr530 as a key amino acid involved in catalysis. A novel 2,3‐difluorosialic acid derivative showed prolonged enzyme inhibition and was found to react and form a covalent bond with Tyr530. Furthermore, the novel derivative exhibited enhanced potency in virus blockade assays relative to its Neu2en analogue. These outcomes open the door for a new generation of potent inhibitors against hPIV‐3 HN.     

Use of light and scanning electron microscopy to examine colonisation of barley rhizosphere by the nematophagous fungus Verticillium chlamydosporium

Barley roots were readily colonised by the nematophagous fungus Verticillium chlamydosporium. Light microscopy (LM) but also low temperature scanning electron microscopy (LTSEM) revealed details of the colonisation process. Hyphae were found on the rhizoplane often with dictyochlamydospores. Hyphae of V. chlamydosporium penetrated epidermal cells, often by means of appressoria. A hyphal network was formed in epidermal and cortical cells. Likewise, hyphal coils were found within root cells next to transverse cell walls. Cortical cells were the limits of fungal colonisation, since no hyphae were seen in the vascular cylinder. Modifications of root cell contents (phenolic droplets and callose appositions) were common three weeks after inoculation with V. chlamydosporium. These features may indicate induction of plant defence reactions in late stages of root colonisation by the fungus. Both LTSEM and LM have proved extremely useful to describe root colonisation by the fungus. The results found may have implications in the mode action of nematophagous fungi against plant parasitic nematodes.     

The asymptotic behavior of the R/S statistic for fractional Brownian motion

This paper provides a proof of the fact that asymptotically the R/S statistic and the self-similarity index of fractional Brownian motion agree in the expectation sense. In particular for fractional Gaussian noise time series, the R/S statistic is an estimator of the self-similarity index H. We also show that two other methods for estimating H yield consistent estimators.     

New insights into the Sn underpotential deposition on Au(100)

The underpotential deposition (UPD) of Sn in the system Au(100)/Sn²⁺, SO₄^2? has been studied by classical electrochemical techniques and in situ scanning tunneling microscopy. The results show that the Sn UPD initiates at relatively high potentials with the formation of a quasi‐hexagonal structure characterized as Au(100) ? (√2 × 7)R45°. This expanded overlayer contributes to the modification of the surface morphology which exhibits flat terraces with step edges showing angles of 60 or 120°. At lower potentials two‐dimensional (2D) islands are formed which tend to grow, causing a coverage increase. In the underpotential region close to the formation of the 3D bulk phase the long time polarization experiments indicate the formation of different Au–Sn alloy phases. Copyright © 2011 John Wiley & Sons, Ltd.     

Optical chemosensors and reagents to detect explosives

This critical review is focused on examples reported from 1947 to 2010 related to the design of chromo-fluorogenic chemosensors and reagents for explosives (141 references).     

13C Hyperfine Interactions in t-(13CH)x Studied by Electron Spin echoes

Electron Spin Echo (ESE) experiments have been performed on 9956 ^l3C-enriched trans-(CH)x. Strong modulation 1s observed In the envelope traced by the decay of the spin echoes. This modulation arises from the interaction of the paramagnetic defect with ¹³C nuclei. The electron-nuclear hyperfine coupling may be determined by Fourier transformation of the time domain signal. At 6K we find a maximum hyperfine coupling of 1.75 Mhz.     

On flipping the classroom in large first year calculus courses

Over the course of two years, 2012--2014, we have implemented a ‘flipping’ the classroom approach in three of our large enrolment first year calculus courses: differential and integral calculus for scientists and engineers. In this article we describe the details of our particular approach and share with the reader some experiences of both instructors and students.