Ultrasound-assisted green synthesis of nanocrystalline ZnO in the ionic liquid [hmim][NTf2]

For the first time, zinc oxide nanoparticles have been synthesized by the sonochemical method in an ionic liquid, 1-hexyl-3-methylimidazolium his (trifluoromethylsulfonyl) imide, liquid [hmim][NTf2] as a solvent. The morphology and structure of ZnO nanoparticles have been characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). A possible mechanism is proposed to explain the formation of ZnO nanostructures. (C) 2008 Elsevier B.V. All rights reserved.

LIQUID-CHROMATOGRAPHY THERMOSPRAY MASS-SPECTROMETRIC ASSAY FOR TRENBOLONE IN BOVINE BILE AND FECES

A liquid chromatography-thermospray mass spectrometric assay was developed and validated to confirm the presence of illegal residues of the synthetic androgenic growth promoter, trenbolone acetate, in cattle. The assay was specific for 17alpha-trenbolone, the major bovine metabolite of trenbolone acetate. Methods were developed for the determination of 17alpha-trenbolone in both bile and faeces, the most appropriate matrices for the control of trenbolone acetate abuse. The clean-up.procedure developed relied on enzymatic hydrolysis, followed by sequential liquid-liquid and liquid-solid extraction. The extracts were then subjected to immunoaffinity chromatography. 17alpha-Trenbolone was detected by selected ion monitoring at m/z 271 using positive ion thermospray ionisation. The limit of detection was approximately 0.5 ng/g in faeces and 0.5 ng/ml in bile.

Comparison of the efficiences of enzymatic and chemical hydrolysis of (nortestosterone and diethylstilboestrol) glucuronides in bovine urine

Residues of 19-nortestosterone (19-NT) and diethylstilboestrol (DES) are excreted in bovine urine, mainly conjugated to glucuronic acid. Prior to quantification, urine must be deconjugated, which is commonly performed by enzymatic or chemical hydrolysis. The efficiencies of two enzymatic and two chemical deconjugation methods were studied. The range of efficiencies obtained for DES were 51.8% (beta -glucuronidase, incubation at 37 degreesC overnight) and 2.7% (methanolic HCl), respectively. Similarly, efficiencies for NT ranged from 43.1% (beta -glucuronidase, incubation at 55 degreesC for 2 h) to 12.7% (methanolic HCl). The results highlight that within control laboratories significant underestimation of drug residue content in samples may occur, due to poor deconjugation. (C) 2001 Elsevier Science B.V. All rights reserved.

Enzymatic and chemoenzymatic synthesis of arene trans-dihydrodiols

Several potential approaches to the enzyme-catalysed synthesis of arene trans-diols have been examined including epoxidation/hydrolysis, bis-benzylic hydroxylation, cis-dihydroxylation/alcohol dehydrogenation/ketone reduction, cisdihydroxylation/cis-trans isomerisation. and multi-enzyme synthesis of trans-dihydrodiol secondary metabolites from primary metabolites. The lack of general applicability of these enzymatic methods has led to the development of several chemoenzymatic routes for the synthesis of a series of trans-dihydrodiols from the readily available cis-dihydrodiol precursors. Partial hydrogenation of cis-dihydrodiol metabolites to yield the corresponding cis-tetrahydrodiols followed by a regioselective Mitsunobu inversion process gave trans-tetrahydrodiols that were in turn converted to trans-dihydrodiols. The formation of anti-benzene dioxides or iron tricarbonyl complexes from the corresponding cis-dihydrodiol precursors provided shorter and more convenient chemoenzymatic routes to trans-dihydrodiols. The application of cis-dihydrodiol metabolites of polycyclic azaarenes in the synthesis of the corresponding arene oxides followed by chemical hydrolysis provides a convenient route to trans-dihydrodiols. (C) 2002 Elsevier Science B.V. All rights reserved.

Effect of in vitro non-enzymatic glycosylation of human skin collagen on susceptibility to collagenase digestion

The effect of glycosylation on susceptibility of skin collagen to collagenase digestion was studied in a skin sample obtained at autopsy from the interscapular region of a 24 year old white male who had died of an acute illness and who had no history of diabetes. Homogeneous suspensions of insoluble collagen were prepared, and were incubated in 50 mmol l-1 dextrose at pH 7.35 and 37 degrees C for 7 days. Non-enzymatic glycosylation measured by the weak acid hydrolysis/thiobarbituric acid method increased from 13.1 +/- 1.0 (n = 5) to 45.2 +/- 5.5 (n = 8) nmol fructose per 10 mg collagen (P less than 0.001). Digestion of collagen using clostridial collagenase was monitored by measuring (a) hydroxyproline content and (b) absorption at 206 nm of the supernatant after centrifugation to remove substrate. The rate of digestion was similar in glycosylated and control collagen. We conclude that the ketoamine link formed in non-enzymatic glycosylation does not increase the resistance of collagen to enzymatic digestion. The possibility remains that subsequent rearrangement of this link could be important in this respect.

Ultrasound entropy may be a new non-invasive measure of pre-clinical vascular damage in young hypertensive patients

Background: The identification of pre-clinical microvascular damage in hypertension by non-invasive techniques has proved frustrating for clinicians. This proof of concept study investigated whether entropy, a novel summary measure for characterizing blood velocity waveforms, is altered in participants with hypertension and may therefore be useful in risk stratification.

Methods: Doppler ultrasound waveforms were obtained from the carotid and retrobulbar circulation in 42 participants with uncomplicated grade 1 hypertension (mean systolic/diastolic blood pressure (BP) 142/92 mmHg), and 26 healthy controls (mean systolic/diastolic BP 116/69 mmHg). Mean wavelet entropy was derived from flow-velocity data and compared with traditional haemodynamic measures of microvascular function, namely the resistive and pulsatility indices.

Results: Entropy, was significantly higher in control participants in the central retinal artery (CRA) (differential mean 0.11 (standard error 0.05 cms(-1)), CI 0.009 to 0.219, p 0.017) and ophthalmic artery (0.12 (0.05), CI 0.004 to 0.215, p 0.04). In comparison, the resistive index (0.12 (0.05), CI 0.005 to 0.226, p 0.029) and pulsatility index (0.96 (0.38), CI 0.19 to 1.72, p 0.015) showed significant differences between groups in the CRA alone. Regression analysis indicated that entropy was significantly influenced by age and systolic blood pressure (r values 0.4-0.6). None of the measures were significantly altered in the larger conduit vessel.

Conclusion: This is the first application of entropy to human blood velocity waveform analysis and shows that this new technique has the ability to discriminate health from early hypertensive disease, thereby promoting the early identification of cardiovascular disease in a young hypertensive population.

Wavelet entropy of Doppler ultrasound blood velocity flow waveforms distinguishes nitric oxide-modulated states

Wavelet entropy assesses the degree of order or disorder in signals and presents this complex information in a simple metric. Relative wavelet entropy assesses the similarity between the spectral distributions of two signals, again in a simple metric. Wavelet entropy is therefore potentially a very attractive tool for waveform analysis. The ability of this method to track the effects of pharmacologic modulation of vascular function on Doppler blood velocity waveforms was assessed. Waveforms were captured from ophthalmic arteries of 10 healthy subjects at baseline, after the administration of glyceryl trinitrate (GTN) and after two doses of N(G)-nitro-L-arginine-methyl ester (L-NAME) to produce vasodilation and vasoconstriction, respectively. Wavelet entropy had a tendency to decrease from baseline in response to GTN, but significantly increased after the administration of L-NAME (mean: 1.60 ± 0.07 after 0.25 mg/kg and 1.72 ± 0.13 after 0.5 mg/kg vs. 1.50 ± 0.10 at baseline, p < 0.05). Relative wavelet entropy had a spectral distribution from increasing doses of L-NAME comparable to baseline, 0.07 ± 0.04 and 0.08 ± 0.03, respectively, whereas GTN had the most dissimilar spectral distribution compared with baseline (0.17 ± 0.08, p = 0.002). Wavelet entropy can detect subtle changes in Doppler blood velocity waveform structure in response to nitric-oxide-mediated changes in arteriolar smooth muscle tone.