Hyperbranched rolling circle amplification as a rapid and sensitive method for species identification within the Cryptococcus species complex

The Cryptococcus species complex contains two closely related basidiomycetous yeasts: Cryptococcus neoformans and C. gattii, which cause cryptococcosis in humans and other animals. The species and varieties are characterized, by different clinical, epidemiological, biochemical and molecular features. The currently used identification methods are either time-consuming or not anymore commercially available. However, a rapid, sensitive and robust assay for the detection of these pathogens is vital for early diagnosis and appropriate treatment decisions. To overcome those limitations, four padlock probes targeting species-specific single nucleotide polymorphisms at the internal transcribed spacers (ITSs) of the RNA gene locus were developed and applied during isothermal hyperbranched rolling circle amplification (HRCA). The probes were tested against 99 samples, including 94 clinical cryptococcal cultures, three closely related Cryptococcus species, and two clinical specimens. The use of the padlock probes and the combination of probe signal amplification by HRCA provided a quick and sensitive assay for the accurate identification of C. neoformans var. grubii, C. neoformans var. neoformans and C. gattii. HRCA was also useful to detect hybrids, when they were heterozygous at the ITS locus. The HRCA results were in agreement with previous genotyping data based on PCR fingerprinting, amplified fragment length polymorphism and ITS sequencing.     

A Mediator‐Free Bienzyme Amperometric Biosensor Based on Horseradish Peroxidase and Glucose Oxidase Immobilized on Carbon Nanotube Modified Electrode

Multiwalled carbon nanotube (CNT) modified glassy carbon electrode immobilized with horseradish peroxidase (HRP) in Nafion coating showed direct electron transfer between HRP enzyme and the CNT‐modified electrode. A mediator‐free bienzyme glucose biosensor based on horseradish peroxidase and glucose oxidase was constructed. The bienzyme biosensor exhibited a high sensitivity for glucose detection at zero applied potential.     

Design and synthesis of novel magnetic core-shell polymeric particles

A novel synthetic strategy was developed for the preparation of magnetic core-shell (MCS) particles consisting of hydrophobic poly(methyl methacrylate) cores with hydrophilic chitosan shells and gamma-Fe2O3 nanoparticles inside the cores via copolymerization of methyl methacrylate from chitosan in the presence of vinyl-coated gamma-Fe2O3 nanoparticles. The magnetic core-shell particles were characterized with transmission electron microscopy, field-emission scanning electron microscopy, particle size and zeta-potential measurements, vibrating sample magnetometry, and atomic force microscopy, respectively. The MCS particles were less than 200 nm in diameter with a narrow size distribution (polydispersity = 1.09) and had a good colloidal stability (critical coagulation concentration = 1.2 M NaCl at pH 6.0). Magnetization study of the particles indicated that they exhibited superparamagnetism at room temperature and had a saturation magnetization of 2.7 A m2/kg. The MCS particles were able to form a continuous film on a glass substrate, where magnetic nanoparticles could evenly disperse throughout the film. Thus, these new materials should be extremely useful in various applications.     

Ruthenium-catalyzed asymmetric epoxidation of olefins using H2O2, part I: synthesis of new chiral N,N,N-tridentate pybox and pyboxazine ligands and their ruthenium complexes

The synthesis of chiral tridentate N,N,N-pyridine-2,6-bisoxazolines 3 (pybox ligands) and N,N,N-pyridine-2,6-bisoxazines 4 (pyboxazine ligands) is described in detail. These novel ligands constitute a useful toolbox for the application in asymmetric catalysis. Compounds 3 and 4 are conveniently prepared by cyclization of enantiomerically pure alpha- or beta-amino alcohols with dimethyl pyridine-2,6-dicarboximidate. The corresponding ruthenium complexes are efficient asymmetric epoxidation catalysts and have been prepared in good yield and fully characterized by spectroscopic means. Four of these ruthenium complexes have been characterized by X-ray crystallography. For the first time the molecular structure of a pyboxazine complex [2,6-bis-[(4S)-4-phenyl-5,6-dihydro-4H-[1,3]oxazinyl]pyridine](pyridine-2,6-dicarboxylate)ruthenium (S)-2 aa, is presented.     

Convenient method for epoxidation of alkenes using aqueous hydrogen peroxide

[reaction: see text] The complex [Ru(tpy)(pydic)] (1a) is an active catalyst for epoxidation of alkenes by aqueous 30% hydrogen peroxide in tertiary alcohols. The protocol is simple to operate and gives the corresponding epoxides in good to excellent yields. Chiral enantiopure [Ru(tpy)(pydic)] complexes have been synthesized and successfully applied in this procedure.     

Spectroscopic Measurement of Scattering Media by Parallel-Detection-Based Optical Coherence Tomography

We report on the spectroscopic optical coherence tomography of highly scattering media using a parallel detection scheme incorporated with an ultrabroadband femtosecond Ti:sapphire laser in the range of 700--880 nm. A plurality of spectrally-resolved reflectance profiles are simultaneously measured in a single longitudinal scan, from which information on the spectral content of the sample is derived. Differential absorption measurements of scattering media with known characteristics are performed to demonstrate the potential use in quantitative analysis.     

Pre-constructed dynamic geometry materials in the classroom – how do they facilitate the learning of ‘Similar Triangles’?

The use of dynamic geometry software (DGS) is becoming increasingly familiar among teachers, but letting students conduct inquiries using computers is still not a welcome idea. In addition to logistics and discipline concerns, many teachers believe that mathematics at the lower secondary level can be learned efficiently through practice alone. Thus, the application of DGS remains limited to demonstration and explanation. This article discusses how a set of pre-constructed dynamic geometry (DG) materials was designed to teach the ‘similar triangles’ concept. The reactions and behaviour of students with relatively low levels of mathematic achievement are also analysed. Finally, the potential value of pre-constructed DG materials, with lab sheets and teacher intervention, in inquiry activities for junior-level students is discussed.     

Flexible bivariate beta distributions

Bivariate beta distributions which can be used to model data sets exhibiting positive or negative correlation are introduced. Properties of these bivariate beta distributions and their applications in Bayesian analysis are discussed. Three methods for parameter estimation are presented. The performance of these estimators is evaluated based on Monte Carlo simulations. Examples are provided to illustrate how additional parameters can be introduced to gain even more modeling flexibility. A possible extension of the proposed bivariate beta model and a multivariate generalization are also discussed.