Evaluation of VIDAS Immuno-Concentration Salmonella (ICS)/VIDAS Salmonella (SLM) immunoassay method for detection of Salmonella in selected foods (Method Modification 2001.09): collaborative study

A new method for detection of Salmonella in foods in a minimum of 24 h was adopted as an AOAC Official First Action Method for selected foods (2001.09) using both the VIDAS Immuno-Concentration Salmonella (ICS) and VIDAS Salmonella (SLM) methods.     

The preparation of phenacylpyrazoles,acylpyrazoles, imidazolylisoxazoles and imidazolylpyrazoles from c(α)-dianions of oximes,phenylhydrazones and acylhydrazones

C(α),O-Dilithiooximes, C(α), N-dilithiophenylhydrazones, or C(α), N-dilithioacylhydrazones were prepared in an excess of lithium diisopropylamide (LDA) and condensed with a variety of esters followed by acid-cyclization to give substituted isoxazoles and pyrazoles.     

Gentamicin assay in human serum by solid-phase extraction and capillary electrophoresis

We describe the development of a capillary electrophoresis method for the determination of gentamicin C1, C1a, C2a, and C2 components in human serum. Using a weak cation-exchanger with 20 mM phosphate buffer, pH 7.4, 200 mM borate buffer, pH 9.0, and ammonia/methanol, solid-phase extraction (SPE) of gentamicin components from the human sera was performed. The extract was derivatized with 1,2-phthalic dicarboxaldehyde/mercaptoacetic acid reagent. The derivatives were separated with a background electrolyte comprising 60 mM 2-(N-cyclohexylamino)ethanesulfonic acid (CHES) buffer at pH 9.5 containing 31.6% m/v methanol, and quantified with UV-light absorption detection at 230 nm. The identity of the gentamicin components was confirmed by mass spectrometry. The SPE recovery of the gentamicin ranged from 78% to 93%. The calibration curves were linear from the concentration limit of quantitation (LOQ) to 30 mg/L for the gentamicin mixture. The LOQ for gentamicin C1 was 0.33 mg/L, for C2a 0.23 mg/L, C2 0.25 mg/L, C1a 0.27 mg/L and the concentration limit of detection (LOD) for C1 was 0.15 mg/L, C2a 0.11 mg/L, C2 0.12 mg/L, C1a 0.13 mg/L. Intra-assay relative standard deviation (RSD) values were for C1 (5%), C1a (7%), C2 (6.5%) and C2a (9%); inter-assay RSD values were for C1 (11%), C1a (13.3%), C2 (15%) and C2a (14%). The Pearson's correlation between capillary electrophoresis and immunoassay revealed a linear relationship between these two techniques with r = 0.9. This method for determination of gentamicin C1, C1a, C2a, and C2 in human serum can thus be used in the entire therapeutic concentrations range of gentamicin.     

Probing of individual semiconductor nanowhiskers by TEM-STM.

Along with rapidly developing nanotechnology, new types of analytical instruments and techniques are needed. Here we report an alternative procedure for electrical measurements on semiconductor nanowhiskers, allowing precise selection and visual control at close to atomic resolution. We use a combination of two powerful microscope techniques, scanning tunneling microscopy (STM) and simultaneous viewing in a transmission electron microscope (TEM). The STM is mounted in the sample holder for the TEM. We describe here a method for creating an ohmic contact between the STM tip and the nanowhisker. We examine three different types of STM tips and present a technique for cleaning the STM tip in situ. Measurements on 1-microm-tall and 40-nm-thick epitaxially grown InAs nanowhiskers show an ohmic contact and a resistance of down to 7 kOmega.     

Highly enantio- and diastereoselective one-pot synthesis of acyclic epoxy alcohols and allylic epoxy alcohols

In this report, we outline a highly enantio- and diastereoselective one-pot method for the efficient synthesis of synthetically useful acyclic epoxy alcohols and allylic epoxy alcohols. Our method takes advantage of a highly enantioselective C-C bond-forming reaction to set the initial chirality. The resulting allylic zinc alkoxide intermediate is then epoxidized in situ using either dioxygen or TBHP in the presence of a titanium tetraalkoxide. Epoxy alcohols with up to three contiguous stereocenters are formed in one pot with excellent enantio- and diastereoselectivity. In cases where the zinc alkoxide intermediates contain two different allylic olefins, the more electron-rich double bond is chemoselectively epoxidized to afford an allylic epoxy alcohol. This method represents a highly efficient, stereoselective, and chemoselective approach to the synthesis of a wide range of useful epoxy alcohol and allylic epoxy alcohol products that were previously difficult to access.     

Molecular modeling,NMR spectroscopy,and conformational analysis of 3′,4′-anhydrovinblastine

The assignment of the proton spectrum of 3′,4′-anhydrovinblastine is reported. Assignments are made for several protons for which only approximate assignments were available previously. Homonuclear TOCSY and ROESY spectra were utilized in conjunction with HMQC and HMBC spectra in making the assignment. Correlations in the ROESY spectrum suggested a preferred conformation of the cleavamine (upper) portion of 3′,4′-anhydrovinblastine in which the 21-methyl of the 20/21 ethyl group of the vindo-line (lower) portion is in proximity to the H14′ and 16′-NH resonances of the cleavamine. In a Monte Carlo search, the global minimal energy structure was oriented with the 16-methoxyl group oriented toward the H14′ and 16′-NII resonances. Two other structures, the second and tenth lowest in energy, 0,2 kJ and 8 kJ higher in energy, respectively, brought the 21-methyl group in proximity to the H14′ and 16′-NH resonances in a fashion consistent with the ROESY data. The preferred solution conformation of 3′,4′-anhy-drovinblastine is consistent with the reported solution conformation of vinblastine.     

Method development and validation for the analysis of didanosine using micellar electrokinetic capillary chromatography

A selective MEKC method was developed for the analysis of didanosine in bulk samples. Successful separation of didanosine from 13 of its potential impurities, derived from the various synthetic preparation procedures, was achieved. As CZE gave poor separation selectivity, MEKC was preferable. The use of EKC allowed achievement of the separation in a significantly shorter time than conventional HPLC. An anionic long-chain surfactant, lithium dodecyl sulfate (LiDS), was used as the pseudostationary phase and sodium tetraborate buffer as the aqueous phase. In order to obtain the optimal conditions and to test the method robustness, a central composite response surface modeling experiment was performed. The optimized electrophoretic conditions include the use of an uncoated fused-silica capillary with a total length of 40 cm and an ID of 50 microm, a BGE containing 40 mM sodium tetraborate and 110 mM LiDS at pH 8.0, an applied voltage of 18.0 kV, and the capillary temperature maintained at 15 degrees C. The method was found to be robust. The parameters for validation such as linearity, precision, and sensitivity are also reported. Three commercial bulk samples were analyzed with this system.     

Chemical and Pharmacological Potential of Coccoloba cowellii,an Endemic Endangered Plant from Cuba

Coccoloba cowellii Britton (Polygonaceae) is an endemic and critically endangered plant that only grows in Camagüey, a province of Cuba. In this study, a total of 13 compounds were identified in a methanolic leaf extract, employing a dereplication of the UHPLC-HRMS data by means of feature-based molecular networking (FBMN) analysis in the Global Natural Products Social Molecular Network (GNPS), together with the interpretation of the MS/MS data and comparison with the literature. The major constituents were glucuronides and glycosides of myricetin and quercetin, as well as epichatechin-3-O-gallate, catechin, epicatechin and gallic acid, all of them being reported for the first time in C. cowellii leaves. The leaf extract was also tested against various microorganisms, and it showed a strong antifungal effect against Candida albicans ATCC {"type":"entrez-nucleotide","attrs":{"text":"B59630","term_id":"2614348"}}B59630 (azole-resistant) (IC₅₀ 2.1 µg/mL) and Cryptococcus neoformans ATCC {"type":"entrez-nucleotide","attrs":{"text":"B66663","term_id":"2640641"}}B66663 (IC₅₀ 4.1 µg/mL) with no cytotoxicity (CC₅₀ > 64.0 µg/mL) on MRC-5 SV2 cells, determined by the resazurin assay. Additionally, the extract strongly inhibited COX-1 and COX-2 enzyme activity using a cell-free experiment in a dose-dependent manner, being significantly more active on COX-1 (IC₅₀ 4.9 µg/mL) than on COX-2 (IC₅₀ 10.4 µg/mL). The constituents identified as well as the pharmacological activities measured highlight the potential of C. cowellii leaves, increasing the interest in the implementation of conservation strategies for this species.     

Intermediate precision study on a capillary electrophoretic method for chlortetracycline

We describe an intermediate precision study on a capillary electrophoretic (CE) method for chlortetracycline. It is shown how in one setup the influence of the factors time, analyst, and equipment on the precision can be investigated. As different types of CE equipments were included, the transferability of the method could be examined. Both the qualitative and quantitative aspect of the method were investigated. It was shown that small adaptations in method conditions can have a large influence on the method transferability. Although the method could be transferred to different types of CE equipments, the precision of the method was found poor when the between-equipment variability was taken into account. Despite the use of an internal standard, the between injection variability was found rather high.