Efficient enantioselective synthesis of condensed and aromatic-ring-substituted tyrosine derivatives

An efficient access to both condensed and conjugated tyrosine analogues of high enantiomeric purity is described. Novel ring-substituted tyrosines were synthesized by Suzuki cross couplings of appropriately protected l-3-iodotyrosine with a series of activated and deactivated boronic acid derivatives to achieve the target compounds in high yields. d- and l-4-hydroxy-1-naphthylalanines were readily prepared from the corresponding alpha-enamide in two different approaches, by asymmetric hydrogenation as well as by unselective hydrogenation and enzymatic resolution of the racemic mixture.     

A memetic Differential Evolution approach in noisy optimization

This paper proposes a memetic approach for solving complex optimization problems characterized by a noisy fitness function. The proposed approach aims at solving highly multivariate and multi-modal landscapes which are also affected by a pernicious noise. The proposed algorithm employs a Differential Evolution framework and combines within this three additional algorithmic components. A controlled randomization of scale factor and crossover rate are employed which should better handle uncertainties of the problem and generally enhance performance of the Differential Evolution. Two combined local search algorithms applied to the scale factor, during offspring generation, should enhance performance of the Differential Evolution framework in the case of multi-modal and high dimensional problems. An on-line statistical test aims at assuring that only strictly necessary samples are taken and that all pairwise selections are properly performed. The proposed algorithm has been tested on a various set of test problems and its behavior has been studied, dependent on the dimensionality and noise level. A comparative analysis with a standard Differential Evolution, a modern version of Differential Evolution employing randomization of the control parameters and four metaheuristics tailored to optimization in a noisy environment has been carried out. One of these metaheuristics is a classical algorithm for noisy optimization while the other three are modern Differential Evolution based algorithms for noisy optimization which well represent the state-of-the-art in the field. Numerical results show that the proposed memetic approach is an efficient and robust alternative for various and complex multivariate noisy problems and can be exported to real-world problems affected by a noise whose distribution can be approximated by a Gaussian distribution.     

Evaluation of sample preparation methods for elastomer digestion for further halogens determination

In this work, three sample preparation methods were evaluated for further halogen determination in elastomers containing high concentrations of carbon black. Samples of nitrile-butadiene rubber, styrene-butadiene rubber, and ethylene-propylene-diene monomer elastomers were decomposed using oxygen flask combustion and microwave-induced combustion (MIC) for further Br and Cl determination by ion chromatography (IC), inductively coupled plasma optical emission spectrometry (ICP OES), and inductively coupled plasma mass spectrometry (ICP-MS). Extraction assisted by microwave radiation in closed vessels was also evaluated using water or alkaline solution. Digestion by MIC was carried out using 50 mmol l⁻¹ (NH₄)₂CO₃ as the absorbing solution. The effect of the reflux step was also evaluated. Accuracy was evaluated using certified reference materials with polymeric matrix composition and by comparison of results using neutron activation analysis. Agreement for Br and Cl was better than 95% by MIC using 5 min of reflux, and no statistical difference was found using IC, ICP OES, and ICP-MS for determination of both analytes. For MIC, the relative standard deviation (RSD) was lower than 5%. Using extraction in closed vessels, a high amount of residues was observed, and recoveries were lower than 45% for both analytes. For oxygen flask combustion, the agreement was similar using MIC but RSD was higher (20%). The residual carbon content, an important parameter used to evaluate the digestion efficiency, was always below 1% for MIC. Using MIC, it was possible to digest elastomers with high efficiency, resulting in a single solution suitable for halogen determination by different techniques.     

Identification of regioisomers in a series of N-substituted pyridin-4-yl imidazole derivatives by regiospecific synthesis,GC/MS,and 1H NMR

The regiospecific synthesis of 2a (Scheme 3), a novel and potent pyridinyl imidazole inhibitor of p38 MAP (mitogen-activated protein) kinase, and the regioselective preparation of its regioisomer 2b (Scheme 4) are described. Chromatographic and spectroscopic data are presented, which in this class of compounds allow the unambiguous identification of regioisomers prepared by a nonregiospecific synthetic strategy. Biological data demonstrating the importance of the correct regiochemistry for inhibition of p38 are given.     

The minimum number of components in 4-regular perfect systems of difference sets

The number of components m in regular (m, 5, c)-systems is given in the literature to date by the inequality m ? 4c ? 2 (Bermond et al., “Proceedings, 18th Hungarian Combin. Colloq.”, North-Holland, Amsterdam, 1976). The case m = 4c ? 2 is called extremal. It is proved that (4c ? 2, 5, c)-systems do not exist. An example of a (4c, 5, c)-system with c = 2, is given. Since, in a 4-regular system, m must be even, loc. cit., it is concluded that the lower bound on the number of components is given by m >/ 4c.     

Differences between predicted and observed sequences in Saccharomyces cerevisiae

We recently studied the protein composition of a Saccharomyces cerevisiae wine yeast strain (K310) of enological interest. About 2,500 spots of 8-250 kDa observed molecular mass were resolved by two-dimensional gel electrophoresis. Experimental molecular masses and isoelectric points were calculated for most of them. Twenty-seven proteins were subjected to Edman microsequencing. N-terminal sequences of 12/27 proteins were determined, whereas internal sequences of 6/27 proteins were obtained following in situ proteolysis. Comparison between the experimental data and those reported in the SWISS-PROT database revealed some differences between genotypic and phenotypic sequences. These are indicative of the changes a protein can undergo with respect to the primary structure coded by the genomic DNA. Our results highlight the need to complement genomic analysis with detailed proteomics in order to refine the vast amount of information provided by DNA sequencing and to find an exact correlation between genome and proteome.     

Nuclear magnetic resonance spectroscopic method for the estimation of competitive equilibrium constants

A nuclear magnetic resonance method is described which yields precise estimates of competitive equilibrium constants for systems in which two or more complexing agents compete for common species. Chemical-shift data under rapid exchange conditions are required, but neither analytical not equilibrium concentrations are needed. The method is demonstrated by estimating equilibria of proton exchange between aniline and pyridinium ion, proton exchange between triethylamine and diisopropylammonium ion, and cyclohexaamylose exchange between m- and p-hydroxybenzoic acids. The precisions of the equilibrium constants are similar to or better than those obtained from classical methods and are relatively free from interferences.     

Development of a liquid chromatography-tandem mass spectrometry method for the identification of natural androgen steroids and their conjugates in urine samples

An analytical procedure for the determination of natural steroids and their conjugates was developed and applied to bovine and human urine. Fifteen compounds (free and conjugated) after extraction by solid-phase were identified by liquid chromatography-tandem mass spectrometry (LC-MS-MS) in multiple reaction monitoring (MRM). Free and conjugated steroids were detected all together in the same chromatographic analysis respectively in positive and negative ionization. This procedure reveals to be time-saving, because it overcomes the need of further sample pre-treatment steps, such as enzymatic hydrolysis and derivatisation.The recovery for each compound was around 80%. Limit of detection of each steroid free or conjugated has been evaluated.     

The planning of marketing strategies in consumer credit: an approach based on graphical chain models for ordinal variables

This paper explores the potential of graphical chain models in defining marketing strategies in the consumer credit field. When ordinal variables are involved, the potential can be increased by exploiting the ordinal scale of variables. In the presented research, the effectiveness of ordinal methods is analysed in three important activities for building a score-card: (1) in coarse classifying of variables, (2) in model selection and (3) in measuring the prediction accuracy of the model.     

Amorphous silicon-carbon films prepared by reactive evaporation

Summary An ion-beam-assisted deposition (IBAD) technique, based on reactive evaporation using hydrogen/ methane gas mixture, has been used for the preparation ofa-Si_1−x C _x : H films. Measurements are reported on the composition, optical gap, infra-red vibrational absorption bands and on the electrical dark-conductivity temperature dependence to verify the reliability of this deposition method. On increasing the compositional parameterx up to 0.35, the IR results show an increasing hydrogenation and the presence of Si-CH₃ units in addition to the ones with the carbon fully coordinated with the silicon, while the optical-gap and the dark-conductivity activation energies reached the values of 2.44 eV and 0.77 eV, respectively. The authors of this paper have agreed to not receive the proofs for correction