Palladium complexes with simple iminopyridines as catalysts for polyketone synthesis.

Four iminopyridines (N-N') differing in the nature of the substituents on the iminic carbon and on the ortho positions of the aryl ring (H or CH3) on the iminic nitrogen were used for the synthesis of neutral and monocationic palladium(ii) complexes of general formulae [Pd(CH3)Cl(N-N')] and [Pd(CH3)(NCCH3)(N-N')][PF6]. The detailed NMR characterization in solution highlighted that: (i) for both series of complexes, the Pd-CH3 signal is progressively shifted to a lower frequency on increasing the number of methyl groups on the ligand skeleton; (ii) for the neutral derivatives, the chemical shift of the (15)N NMR signals, determined through {(1)H,(15)N}-HMBC spectra, is significantly affected by the coordination to palladium; (iii) the coordination induced shift (CIS) of the nitrogen atom trans to the CH3 ligand is smaller than the other. The structure in the solid state for the neutral derivatives with all the four ligands was solved, pointing out that: (iv) the Pd-C bond distance increases with the basicity of the nitrogen-donor ligand; (v) the Pd-N bond distance correlates well with the CIS value. The combining of the solution and solid state structural features allows stating that: (vi) the Pd-CH3 singlet is a good probe for the electron donor capability of the ligand; (vii) the CIS value might be used as a probe for the strength of the Pd-N bond. All monocationic complexes generated active catalysts for the CO/vinyl arene copolymerization, leading to prevailingly syndiotactic polyketones. The catalyst performances, both in terms of catalyst productivity and polymer molecular weight, correlate well with the precatalyst structural features.

Trace metals in arcid clam Scapharca inaequivalvis: effects of molluscan extracts on bioluminescent bacteria.

The relationship between a supposed effect of molluscan extracts on bioluminescent bacteria and metal concentrations in the extracts was investigated. For this purpose a biotoxicological assay based on bioluminescent bacteria (BLB) and extracts from metal exposed molluscs, Scapharca inaequivalvis, was optimized to monitor Cd and Cu marine pollution. Cu and Cd concentrations increased in tissues of experimentally exposed molluscs. Molluscan extracts inhibited the bacterial luminescence, the inhibition decreasing as the time of mollusc exposure to metals increased, suggesting a reduction of the "bioactive" metals. In regard to the use of BLB test in environmental monitoring, the analysis of Cu, Cd, and metallothionein (MT) was first performed in tissues from molluscs collected in three different areas of Northern Adriatic Sea. Metal concentrations reached maximum values in the gills, while Cd was mostly bound to MT in the kidney. Significant differences in metals and MT concentrations were found depending on the sampling sites. The biotoxicological assay resulted slightly correlated with the biochemical parameters.

Bioluminescent bacteria assay of veterinary drugs in excreta of food-producing animals.

The residues of pharmacological treatments on food-producing animals, present in the manure dispersed on agricultural land, can impact environmental and human health through toxic, genotoxic, and drug-resistance development effects. Biotoxicity assays can easily reveal the presence of noxious substances and those based on bioluminescent bacteria (BLB) are particularly simple and rapid. A BLB assay was developed as microplate format by using various strains of Vibrio sp. and was employed to evaluate their response to pure antibiotic solutions and to residues extracted from excreta of antibiotic treated pigs and turkeys. The residues were quantified by HPLC analysis. The BLB assay can be proposed as an easy-to-perform screening tool to assess the presence of residues due to undeclared current, or recently ended, pharmacological treatments, as well as to evaluate their permanence in manure.

Application of matrix solid phase dispersion to the determination of imidacloprid, carbaryl, aldicarb, and their main metabolites in honeybees by liquid chromatography-mass spectrometry detection.

A method based on matrix solid phase dispersion (MSPD) using C18 as dispersant and dichloromethane-methanol as eluent and liquid chromatography-atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) has been developed for the simultaneous determination of imidacloprid, 6-chloronicotinic acid, carbaryl, aldicarb, aldicarb sulfoxide, and aldicarb sulfone in honeybees. The proposed method was compared with liquid-liquid extraction (LLE) combined with LC-APCI-MS analysis. Spiked blank samples were used as standards to counteract the matrix effect observed in the chromatographic determination. Recovery studies were performed at different fortification levels. Average recoveries by MSPD varied from 61% of 6-chloronicotinic acid to 99% of aldicarb sulfoxide and relative standard deviations were equal or lower than 14%. Limit of detections ranged from 0.004mgkg(-1) for imidacloprid to 0.09mgkg(-1) for 6-chloronicotinic acid. Results obtained by both methods were compared, MSPD showed higher recoveries and sensitivity than LLE for most pesticides, except for carbaryl. As MSPD is easier to perform, faster, consumes less sample and organic solvents than LLE, its application for pesticide analysis in honeybees is suggested.

Occurrence and distribution of pesticides in the province of Bologna, Italy, using honeybees as bioindicators.

Samples of honeybees (Apis mellifera, n = 92) from 14 beehive monitoring stations located in 3 townships in the province of Bologna were analyzed from April to October 2000. The concentration of 32 organophosphorus pesticides and 5 carbamates was determined through liquid-liquid extraction followed by gas chromatography with a nitrogen-phosphorus detector and liquid chromatography coupled to mass spectrometry using atmospheric pressure chemical ionization in positive and negative ion modes. The most contaminated samples were from Granarolo Emilia where cereals (wheat, sorghum, and corn), sugar beets, and potatoes are the main agriculture products. Thirty-five pesticides were detected, with organophosphorus being the most abundant ones. Malathion was detected in 58% of the samples (mean level 0.360 mg/kg) followed by fenithrothion in 53% of the samples (mean level 0.544 mg/kg) and pirimiphos methyl in 48% of the samples (mean level 0.006 mg/kg). Temporal trends showed that the maximum detection frequency occurred in late spring and was associated with the use of treatment products and less rainfall. The obtained results demonstrated the feasibility of using honeybees for assessing pesticide exposure in agriculture settings.

Automated and manual luminescent assay of antioxidant capacity: analytical features by comparison.

The analytical performances of a manual and a partially automated chemiluminescent (CL) assay, of total antioxidant capacity (TAC) were assessed. In both cases the light emitting reaction involved luminol, horseradish peroxidase and hydrogen peroxyde, but the emission kinetics and the parameters taken into account to calculate TAC values were completely different. The major characteristics expressing the quality of the two analytical methods, i.e. inaccuracy, repeteability and reproducibility, sensitivity, time required for the analysis and detection limit, were estimated by using standard solutions of Trolox. The reliability of the automated method, in comparison with the more validated manual one, was demonstrated testing food samples such as honey, wine and dietary supplements and performing a statistical analysis of the results. The comparison of the two series of data by t-test resulted in p values in the range 0.1-0.01. The time required for the analysis of each sample was reduced to one third using the automated method.

Determination of superoxide dismutase in erythrocytes by a chemiluminescent assay.

A highly rapid chemiluminescent assay for the determination of superoxide dismutase (SOD) activity in erythrocytes was developed. The inhibition of the luminescent emission caused by the decrease of generated superoxide anions was measured. The aim of this work was to verify the application of a non amplified luminol SOD luminescent assay (CLM) in erythrocytes starting from an amplified method already used for the determination of XOD activity in milk (CLME). Both the assays had a detection limit of 3x10(-2)+/-7x10(-3) U/ml of SOD at 2sigma level, and a linear range of activity from 5.2 to 0.03 U/ml of SOD. The imprecision of assays (repeatability) presented coefficients of variations ranging from 3.1 to 7.9% for the CLME method and from 0.6 to 17.7% for CLM method. Both luminescent techniques were compared using a spectrophotometric kit, that had a detection limit of 0.3 U/ml, and showed good agreement.

Chemiluminescent determination of xanthine oxidase activity in milk.

A chemiluminescent method for determining xanthine oxidase (XOD) activity was developed and applied to the assay of milk enzyme activity using a photomultiplier luminometer. Various kinds of milk and cream samples were analysed for XOD content. In pasteurized milk, XOD activity depended on the fat content and in UHT milk it disappeared owing to the heat treatment. Milk sample preparation was very simple, requiring only homogenization at 40 degrees C followed by a 1:10 dilution with UHT ('XOD-free') milk. The assay was carried out at 25 degrees C. The response obtained from XOD standard solutions in milk was linear from 0.1 to 500 enzyme units (U) l-1, but for the actual milk samples values ranged only from 1 to 135 U l-1. The detection limit at 2 SD was 0.1 U l-1 in milk, while in buffer it was 100 times lower. The intra-assay and interassay CV for XOD activity in milk were 6-12%.

Development of a chemiluminescence competitive PCR for the detection and quantification of parvovirus B19 DNA using a microplate luminometer.

BACKGROUND: Quantitative PCR of viral nucleic acids can be useful clinically in diagnosis, risk assessment, and monitoring of antiviral therapy. We wished to develop a chemiluminescence competitive PCR (cPCR) for parvovirus B19. METHODS: Parvovirus DNA target sequences and competitor sequences were coamplified and directly labeled. Amplified products were then separately hybridized by specific biotin-labeled probes, captured onto streptavidin-coated ELISA microplates, and detected immunoenzymatically using chemiluminescent substrates of peroxidase. Chemiluminescent signals were quantitatively analyzed by a microplate luminometer and were correlated to the amounts of amplified products. RESULTS: Luminol-based systems displayed constant emission but had a higher detection limit (100-1000 genome copies) than the acridan-based system (20 genome copies). The detection limit of chemiluminescent substrates was lower (20 genome copies) than colorimetric substrates (50 genome copies). In chemiluminescence cPCR, the titration curves showed linear correlation above 100 target genome copies. Chemiluminescence cPCR was positive in six serum samples from patients with parvovirus infections and negative in six control sera. CONCLUSIONS: The chemiluminescence cPCR appears to be a sensitive and specific method for the quantitative detection of viral DNAs.

The effect of different solvents on the ATP/ADP content and growth properties of HeLa cells.

Testing of the effects of xenobiotics in cultured cells often requires the use of organic solvents to effect suspension of the test agents in cell culture media. However, the toxic effects of the solvents themselves may introduce artifacts, which obscure interpretation of the experimental results. In this article, the toxicity of different solvents commonly used for solvation of a variety of xenobiotic agents was studied. We show that ethanol, acetone, isooctane, methanol, and hexane were considerably less toxic than the more commonly used solvent, DMSO, when ATP content and growth rates of HeLa cells exposed to these solvents was measured.

A chemiluminescent flow sensing device for determination of choline and phospholipase D activity in biological samples.

A chemiluminescent flow-sensing device for the determination of phospholipase D (PLD) activity and/or choline (Ch) in biological samples using choline oxidase (ChO) and horseradish peroxidase (HRP) immobilized on Eupergit C (polymer beads of methacrylamide, N-methylene-bis-methacrylamide, and allyl-glycidyl-ether) was developed. The best results were obtained with immobilized ChO and HRP at a polymer beads wet weight ratio of 16:1. The optimized parameters of the developed sensing device were 56 microM luminol in working solution; sample volume, 60 microliters; flow rate, 0.3 ml/min; and sample throughput, 15/h. The detection limit (3 SD) using a luminescent enhancer was 1.2 microM for Ch, corresponding to 0.167 mIU of PLD activity per milliliter. Without enhancer the values were 3.0 microM and 0.417 mIU, respectively. The Ch recovery varied between 80.4 and 109%. The biological samples quenched the luminescent light to different extents, and this matrix effect was readily overcome by measuring the luminescent signal of added Ch standard. The flow biosensor was used for the determination of PLD in samples of different origin, including rape seeds during maturation.