The symmetric eigenvalue complementarity problem

In this paper the Eigenvalue Complementarity Problem (EiCP) with real symmetric matrices is addressed. It is shown that the symmetric (EiCP) is equivalent to finding an equilibrium solution of a differentiable optimization problem in a compact set. A necessary and sufficient condition for solvability is obtained which, when verified, gives a convenient starting point for any gradient-ascent local optimization method to converge to a solution of the (EiCP). It is further shown that similar results apply to the Symmetric Generalized Eigenvalue Complementarity Problem (GEiCP). Computational tests show that these reformulations improve the speed and robustness of the solution methods.

     

Compositions for health products obtained by treatment of tomato with beta-cyclodextrin

The aim of this work was to produce lycopene-containing powders from tomato products by a solvent-free method making use of β-cyclodextrin (βCD). Powders were prepared by spray-drying a tomato concentrate (TC), one of the most bioavailable form of lycopene, after mechanical treatment with βCD in different weight ratios. The obtained product was centrifuged to eliminate partly food matrix and characterized for the amount of lycopene hydrodispersed/hydrosolubilized in the aqueous fraction. The chemical antioxidant activity of sera was evaluated too. Powders obtained by spray-drying sera exhibited good flow properties, a lycopene content between 0.4 and 1.09 mg/g and excellent water dispersability. The process developed, which makes use of βCD for the treatment of tomato products, turns to be of great interest to obtain a bulk material for nutraceuticals displaying superior biovailability of lycopene.     

Chromatography of plasmid DNA

Liquid chromatography plays a central role in process-scale manufacturing of therapeutic plasmid DNA (pDNA) for gene therapy and DNA vaccination. Apart from its use as a preparative purification step, it is also very useful as an analytical tool to monitor and control pDNA quality during processing and in final formulations. This paper gives an overview of the use of pDNA chromatography. The specificity of pDNA purification and the consequent limitations to the performance of chromatography are described. Strategies currently used to overcome those limitations, as well as other possible solutions are presented. Applications of the different types of chromatography to the purification of therapeutic pDNA are reviewed, and the main advantages and disadvantages behind each technique highlighted.     

On-line identification of tropane alkaloids from Erythroxylum vacciniifolium by liquid chromatography-UV detection-multiple mass spectrometry and liquid chromatography-nuclear magnetic resonance spectrometry

The bark of catuaba (Erythroxylum vacciniifolium Martius, Erythroxylaceae), a tree native to the northern part of Brazil, was investigated for its alkaloid content. With the aim of obtaining preliminary structure information on-line, the alkaloid extract was analysed by high-performance liquid chromatography coupled to diode array UV detection, to mass spectrometry and to nuclear magnetic resonance. Interpretation of on-line spectroscopic data obtained from this extract led to structural elucidation of six new alkaloids and partial identification of 18 potentially original alkaloids bearing the same tropane skeleton esterified in positions 3 and 6 by 1-methyl-1H-pyrrol-2-carboxylic acid and/or 4-hydroxy-3,5-dimethoxybenzoic acid.     

Utilisation of 1,3-dialkylimidazolium-2-carboxylates as CO2-carriers in the presence of Na and K: application in the synthesis of carboxylates, monomethylcarbonate anions and halogen-free ionic liquids

1,3-Dialkylimidazolium-2-carboxylate compounds have recently been fully characterised. Here we describe the utilisation of 1,3-dimethyl (1a) and 1-butyl-3-methyl-imidazolium-2-carboxylate (1b) in a carboxylation reaction with transfer of the CO₂ moiety to benzoylacetone and methanol for the synthesis, in high yield, of benzoylacetate and monoalkylcarbonate anions, respectively. Conversely, when compounds 1a and b are reacted with carbonylic substrates lacking C-H active bonds, a product resulting from nucleophilic attack of the 1,3-dialkylimidazol-2-ylidene species on the carbonyl moiety is obtained. The reported reactions can find applications in organic synthesis and in the synthesis of halogen-free ionic liquids.     

A thieno-2H-chromene alpha-amino acid derivative: synthesis and photochromic properties

[structure: see text] A new photochromic thieno-2H-chromene alpha-amino acid derivative was prepared by C-N palladium-catalyzed cross-coupling of a bromothieno-2H-chromene with the aminated aromatic side chain of the methyl ester of a N,N-diprotected amino acid. Its good photochromic properties demonstrated by flash photolysis and continuous irradiation indicate a possible application in ophthalmic lenses. It may also be inserted into peptides to give photoinduced reversible structural changes.     

Electrocatalytic Properties of a Novel Poly‐1‐Naphthylamine‐Modified Electrode Using Ascorbic Acid as Molecule Probe

A glassy carbon electrode was modified with an electropolymerized film of 1‐naphthylamine in aqueous solution. The electrocatalytic properties of this modified electrode (ME) were investigated using ascorbic acid (AA) as probe molecule. The electrochemical behavior of AA in buffer solution was examined by voltammetry and amperometry. The results showed that the ME exhibited good electrocatalytic activity towards the oxidation of AA, as a consequence, it can be used as amperometric sensor of this analyte in a flow injection system with good sensitivity. Calibration curves were linear over the concentration range 0.05–1.50 mM with a phosphate buffer solution pH 3 as the carrier, the detection limit was 1 ppm (S/N=3). The methods were applied to the determination of AA in beverages and pharmaceutical products. A good correlation with a reference method was attained.     

31P{1H}-n.m.r. as a tool for identification of ruthenium isomers containing PPh3 or 1,4-bis(diphenylphosphino)butane ligands. X-ray structures of the cis-{RuCl2(PPh3)2 [4,4′-(-X)2-2,2′-bipy]} complexes [X=-H, -Me, -SMe and (-Cl, -Me)]

A series of cis-{RuCl₂(PPh₃)₂[4,4-(X)₂-2,2-bipy]} [cis-chlorines; X=-H, -Me, -SMe, and (-Cl,-Me)] complexes have had their structures determined by single crystal X-ray diffraction. The geometry of these complexes, also determined in CH₂Cl₂ solution by ³¹P{¹H}-n.m.r. spectroscopy, showed that the chemical shifts for the phosphorus atoms are slightly dependent on the pKa of the 4,4-(-X)₂-2,2-bipy ligands.     

Studies on the chromatographic fractionation of Trichoderma reesei cellulases by hydrophobic interaction

This work reports new studies on cellulases fractionation by hydrophobic interaction chromatography. The purification procedure for the Trichoderma reesei cellulase complex consists of gel permeation chromatography on Sephadex G-25M followed by an ultrafiltration step. The concentrated enzyme solution was then fractionated on Sepharose CL-6B modified by covalent immobilization of 1,4-butanediol diglycidyl ether. The influence of the mobile phase composition on the chromatographic behaviour of the T. reesei cellulase complex was investigated. By using 13% (w/v) ammonium sulphate in eluent buffer, a selective separation of beta-glucosidase with a two-fold increase in specific activity and a recovery of 60% cellobiase activity were obtained. Other commercial hydrophobic supports (octyl- and phenyl-Sepharose) were also tested and compared under the same conditions.     

Chemometric studies in the Lagoon of Venice, Italy. Annual evolution of sulphur species and relationship to biogeochemical cycles in lagoon water

During the period March 1997-March 1998 dimethyl sulphide (DMS), dimethylsulphoniopropionate (DMSP) and carbon disulphide (CS2) were determined weekly in the water of the Lagoon of Venice, Italy (at three stations located in the Giudecca Canal, the San Secondo Canal and the Rio di San Nicolò). At the same time, the following hydrological and biological variables were also measured: tide height, temperature, transmittance, fluorescence, pH, salinity, chlorinity, sulphate, ammonia, nitrite, nitrate, phosphate, silicate, chlorophyll a, phaeopigments, phytoplankton (abundance and biomass). Principal component analysis (PCA), applied as a dimension reduction tool, made it possible to summarize multivariate information in a small number of components, which highlighted the relationships between the temporal evolutions of the sulphur compounds with hydrological and biological variables in the seasonal biogeochemical cycle of the lagoon. In particular the overall temporal cycle, which begins with the development of biological activity in late winter and spring, followed by the predominance of degradation processes during the late summer and the remineralization of nutrients in autumn, is clearly described in the plane of the first two principal components, together with the interrelationships between all the relevant variables.