Capillary electrophoresis-mass spectrometry of basic proteins using a new physically adsorbed polymer coating. Some applications in food analysis

A new physically adsorbed capillary coating for capillary electrophoresis-mass spectrometry (CE-MS) of basic proteins is presented, which is easily obtained by flushing the capillary with a polymer aqueous solution for two min. This coating significantly reduces the electrostatic adsorption of a group of basic proteins (i.e., cytochrome c, lysozyme, and ribonuclease A) onto the capillary wall allowing their analysis by CE-MS. The coating protocol is compatible with electrospray inonization (ESI)-MS via the reproducible separation of the standard basic proteins (%RSD values (n = 5) < 1% for analysis time reproducibility and < 5% for peak heights, measured from the total ion electropherograms (TIEs) within the same day). The LODs determined using cytochrome c with total ion current and extracted ion current defection were 24.5 and 2.9 fmol, respectively. Using this new coating lysozymes from chicken and turkey egg white could be easily distinguished by CE-MS, demonstrating the usefulness of this method to differentiate animal species. Even after sterilization at 120 degrees C for 30 min, lysozyme could be detected, as well as in wines at concentrations much lower than the limit marked by the EC Commission Regulation. Adulteration of minced meat with 5% of egg-white could also be analysed by our CE-MS protocol.     

Spectrophotometric determination of nickel by extraction of the complex nickel-purpurin

A simple, sensitive procedure for extractive spectrophotometric determination of nickel has been developed. At pH 8.5, nickel reacts with purpurin (1,2,4-trihydroxyanthraquinone) to form a 1:1 red complex, extractable in methyl isobutyl ketone, with an absorption maximum at 525 nm. The characteristics of the complex, including optimum conditions of formation and extraction, and the adherence to Beer's law, are described. Nickel in cobalt and in iron and aluminum alloys has been determined by this method.     

Solving liquid chromatography mass spectrometry coelution problems in the analysis of environmental samples by multivariate curve resolution

Multivariate curve resolution-alternating least squares (MCR-ALS) is shown to be a powerful tool to resolve coelution problems in liquid chromatograpy-mass spectrometry (LC-MS) in scan mode. This investigation was performed using two types of LC columns, one traditional LC column of 25 cm length with a slow gradient and a shorter LC column of 7.5 cm with a rapid gradient which allowed much faster analysis and save of reagents and solvents. Mixtures of multiple biocide compounds were simultaneously analyzed in standard mixtures and in environmental samples (sediment and wastewater samples) with little sample pretreatment. Using the more traditional LC 25 cm column, all biocide compounds were properly resolved by MCR-ALS and quantitatively analyzed with estimated errors always below 20%. When fast chromatography (LC column of 7.5 cm) was used, MCR-ALS resolution of the more strongly coeluted compounds was also achieved but limitations were found in their simultaneous quantitative determination, specially for environmental samples.     

Hypoglycemic activity of a new carbohydrate isolated from the roots of Psacalium peltatum

A new ulopyranose isolated from aqueous extract of roots and rhizomas of Psacalium peltatum has been determined to have hypoglycemic activity at doses of 100 mg/kg, comparable to that of tolbutamide and insulin in alloxan diabetic mice. The skeletal structure of the new compound was established by spectral analysis.     

An unusual 3D coordination polymer based on bridging interactions of the nucleobase adenine

The first 3D coordination polymer containing a nucleobase as a bridging ligand, [[Cu2(mu-ade)4(H2O)2][Cu(ox)(H2O)]2 x approximately 14H2O]n (1), has been synthesized by reaction of adenine (Hade) with a basic solution of K2[Cu(ox)2] x 2H2O (ox = oxalato dianion). Compound 1 crystallizes in the trigonal space group R3 with a = b = 31.350(1) angstroms, c = 14.285(1) angstroms, V = 12158.7(10) angstroms3, and Z = 9. X-ray analysis shows a covalent 3D network in which the copper(II) centers are bridged by tridentate mu-N3,N7,N9 adeninate ligands. The compound has relatively large, nanometer-sized tubes associated with the self-assembly process directed solely by metal-ligand interactions. The covalent 3D framework remains intact upon removal of the guest water molecules trapped in the nanotubes. Magnetic measurements indicate an overall antiferromagnetic behavior of the compound.     

Hydrophilic polymer drug from a derivative of salicylic acid: synthesis, controlled release studies and biological behavior

Hydrophilic polymeric drugs bearing "Triflusal" (4-trifluoromethylsalicylic acid), a drug widely used as antithrombogenic agent (Disgren), have been prepared by free radical copolymerization of methacryloyloxyethyl [2-(acetyloxy)-4-(trifluoromethyl)] benzoate (HTRF) and N,N'-dimethylacrylamide (DMA). The reactivity ratios of both monomers have been determined by 1H NMR spectra by applying non-linear least square treatments to the copolymerization equation (terminal model), and the kinetic parameters obtained indicated that the microstructure of copolymer chains is homogeneous, with a random distribution of the active HTRF units along the copolymer chains. That means that for the copolymer system THDMA22 used in this work, HTRF units are mainly isolated in relatively long DMA sequences. Therefore, in this structure the intramolecular interactions between adjacent HTRF units are negligible. Release of Triflusal from THDMA22 has been studied in vitro using buffered solutions at pH = 2, 7.4 and 10 and 37 degrees C. The system showed an interesting pseudo-zero order release profile at pH = 7.4 during several months. It has been also evaluated the pharmacological activity and the behavior of the system in contact with biological media. In this sense, we have carried out some in vitro studies about the antiaggregant properties and biocompatibility of THDMA22. Results demonstrate that this copolymer inhibits platelet aggregation in its macromolecular form and presents a good biocompatibility with Human Osteoblastic Cells (HOS).     

Tracking of the effects of the plasticizer on the water uptake and free volume changes of methylcellulose

The structural changes in methylcellulose containing poly(ethylene glycol) (PEG 400) as plasticizer caused by water absorption during storage were evaluated. In order to elucidate the structural changes in the polymer, water‐uptake measurements and positron annihilation lifetime spectroscopy (PALS) were utilized. The PEG concentrations relative to the total polymer content were varied within the range 0–75% w/w. The Doppler‐spectra were characterized by means of the conventional parameters S and W. A transition from a single phase to two phases was found in the methylcellulose films above PEG; a content of 33% w/w. The first step of ageing is merely a conformational change, after which the electron structure remains more or less the same, while both S and W indicate significant changes during the second slow step of ageing. Accurate determination of the plasticizer concentration relating to the single‐phase to two‐phase transition of Metolose‐PEG films has a great impact from the aspect of the application of a stable composition for coating of solid dosage forms. Copyright © 2007 John Wiley & Sons, Ltd.     

Synthesis and catalytic application of octahedral lewis base adducts of dichloro and dialkyl dioxotungsten(VI)

Complexes of the composition W(O)(2)(Cl)(2)L(2) and W(O)(2)(R)(2)L(2) (R = Me, Et; L(2) = bidentate Lewis base ligand) have been prepared and are fully characterized (including an exemplary X-ray crystal structure of W(O)(2)(Cl)(2)(4,4'-di-tert-butyl-2,2'-bipyridine)). This latter compound crystallizes in the orthorhombic space group P2(1)2(1)2(1) with a = 8.3198(1) A, b = 13.3224(2) A, c = 18.0415(2) A, and Z = 4. The title complexes are applied as catalysts in olefin epoxidation catalysis with tert-butyl hydroperoxide (TBHP) as the oxidizing agent. The W(VI) complexes display only moderate turnover frequencies but can be reused several times without loss of catalytic activity. The highest activity can be achieved at reaction temperatures of ca. 90 degrees C. Chloro derivatives are somewhat more active than alkyl complexes, and sterically less crowded complexes show also higher activities than their congeners with bulky ligands L(2). Kinetic examinations show that the catalyst formation is the rate determining step and it is observed that tert-butyl alcohol, the byproduct of the epoxidation reaction, acts as a competitor for TBHP, thus lowering the reaction velocity during the course of the reaction but not irreversibly destroying the catalyst.     

Spectrophotometric and polarographic studies of pyridin-2-aldehyde guanylhydrazone-Fe(II) system

The analytical properties of iron(II)-PAG system are described. The optimal conditions for a spectrophotometric determination of iron are

shown. A determination of Fe(II) with PAG can be performed in a concentration range varying from 0.5 to 4.7 ppm of iron, the molar absorptivity is 1.3 × 10⁴ liters · mol^?1, at 380 nm and the relative error (95% confidence level) is ±0.3% for 1.9 ppm of iron.A polarographic behavior of iron(II)-PAG system has been attempted. Iron gives well-defined diffusion-controlled reduction wave with half-wave potential ?0.42 V at 8.5 pH value. The electrode process is discussed.     

Synthesis of three marine natural sesterterpenolides from methyl isoanticopalate. First enantioselective synthesis of luffolide

[Reaction: see text]. The synthesis of three marine sponge metabolites, luffolide (4), 5, and 6, are described for the first time, establishing the absolute configuration of these compounds. The key intermediate, aldehyde 17, was obtained from methyl isoanticopalate, 11. The addition of 3-furyllithium to 17 and subsequent photochemical oxidation give the gamma-hydroxybutenolide 5 and its epimer at C-16. Sesterterpenolide 6 is obtained by dehydration of 5. From the key aldehyde 17, luffolide (4) was obtained in six steps.