LC�CMS�CMS Method for the Analysis of New Non-Imidazole Histamine H3 Receptor Antagonist 1-[3-(4-tert-Butylphenoxy)propyl]piperidine in Rat Serum��Application to Pharmacokinetic Studies

A sensitive and specific liquid chromatography electrospray ionisation-tandem mass spectrometry method for determination of new non-imidazole histamine H(3) receptor antagonist 1-[3-(4-tert-butylphenoxy)propyl]piperidine (DL76) in rat serum has been developed and validated. Chromatography was performed on a XBridge? C18 analytical column (2.1?×?30?mm, 3.5?μm, Waters, Ireland) with gradient elution using a mobile phase containing acetonitrile and water with an addition of 0.1% of formic acid. Detection was achieved by an Applied Biosystems MDS Sciex (Concord, Ontario, Canada) API 2000 triple quadrupole mass spectrometer. Electrospray ionization (ESI) was used for ion production. The limit of detection in the SRM mode was found to be 0.5?ng?mL(-1). The limit of quantification was 1?ng?mL(-1). The precision and accuracy for both intra- and inter-day determination of DL76 ranged from 1.65 to 15.09% and from 88.74 to 113.43%. The results of this analytical method validation allow to carry out pharmacokinetic studies in rats. The method was used for the pilot study of the pharmacokinetic behavior of DL76 in rats after intravenous administration.     

The identification of synthetic organic pigments in modern paints and modern paintings using pyrolysis-gas chromatography-mass spectrometry

A collection of more than 70 synthetic organic pigments were analysed using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). We report on the analysis of diketo-pyrrolo-pyrrole, isoindolinone and perylene pigments which are classes not previously reported as being analysed by this technique. We also report on a number of azo pigments (2-naphthol, naphthol AS, arylide, diarylide, benzimidazolone and disazo condensation pigments) and phthalocyanine pigments, the Py-GC-MS analysis of which has not been previously reported. The members of each class were found to fragment in a consistent way and the pyrolysis products are reported. The technique was successfully applied to the analysis of paints used by the artist Francis Bacon (1909-1992), to simultaneously identify synthetic organic pigments and synthetic binding media in two samples of paint taken from Bacon's studio and micro-samples taken from three of his paintings and one painting attributed to him.     

Freeze-fracture TEM imaging of robust order in swollen phases of amphiphilic diblock copolymers

We report on the structures exhibited by two different diblock poly(styrene)-b-poly(acrylic acid) (PS-b-PAA) copolymers in water, a selective solvent. Using a combination of X-ray scattering and freeze fracture-transmission electron microscopy (FF-TEM), we show that these structures can be widely swollen while retaining their initial morphology and a high degree of long-range order. The analysis of the FF-TEM pictures also evidences the presence of water crystallites of regular size and shape within the confined water domains. We relate the growth of these crystallites to the high local ionic strength of the water swelling the PAA brushes. Moreover, the confinement of the crystallites growth shows that the swollen phases have a very robust structure, potentially useful for confining colloidal particles.     

Integral geometry analysis of fluorescence micrographs for quantitative relative comparison of protein adsorption onto polymer surfaces

Most methods developed to study protein binding to distinct surfaces can only determine the average amount of adsorbed protein or merely provide (qualitative) information on its spatial distribution. Both these features can be characterized rigorously by integral geometry analysis of fluorescence micrographs. This approach is introduced here to compare the relative protein adsorption onto various polymer surfaces: polystyrene (PS), poly(methyl methacrylate) (PMMA), poly( n-butyl methacrylate) (PnBMA), poly( tert-butyl methacrylate) (PtBMA), and PS(PETA) and cross-linked poly(ethylene oxide) (PEO*(PETA)), admixed with pentaerythritol triacrylate (PETA). The polymeric surfaces were incubated for 15 min in phosphate-buffered saline (pH 7.4) containing 125 mug/mL fluorescently labeled lectins, either lentil lectin (LcH) or concanavalin A (ConA). Fluorescence images were recorded at identical conditions (physiological buffer, same exposure time, magnification, gain). For each image, taken a few times for each polymer, the distribution and average value of the normalized intensity were determined. The results show that the binding of LcH to PS(PETA), PtBMA, PS, PnBMA, PMMA, and PEO*(PETA) can be expressed by the ratio of the following values (mean +/- 95% confidence interval): 0.356 +/- 0.022, 0.298 +/- 0.030, 0.241 +/- 0.014, 0.083 +/- 0.008, 0.039 +/- 0.008, and 0.010 +/- 0.006, respectively. In turn, the relative adsorption of ConA is described by the values 0.252 +/- 0.016, 0.217 +/- 0.014, 0.222 +/- 0.016, 0.046 +/- 0.006, 0.116 +/- 0.008, and 0.006 +/- 0.002, respectively. Low dispersions of fluorescence intensity around average values indicate homogeneous distribution of adsorbed proteins. The introduced approach enables a fast and easy way not only to quantify the relative amount of bound proteins but also to characterize quantitatively the organization of their surface distribution, as demonstrated for patchlike protein adsorption onto the polymer blend surface.     

Interactions between antimicrobial polynorbornenes and phospholipid vesicles monitored by light scattering and microcalorimetry

Antimicrobial polynorbornenes composed of facially amphiphilic monomers have been previously reported to accurately emulate the antimicrobial activity of natural host-defense peptides (HDPs). The lethal mechanism of most HDPs involves binding to the membrane surface of bacteria leading to compromised phospholipid bilayers. In this paper, the interactions between biomimetic vesicle membranes and these cationic antimicrobial polynorbornenes are reported. Vesicle dye-leakage experiments were consistent with previous biological assays and corroborated a mode of action involving membrane disruption. Dynamic light scattering (DLS) showed that these antimicrobial polymers cause extensive aggregation of vesicles without complete bilayer disintegration as observed with surfactants that efficiently solubilize the membrane. Fluorescence microscopy on vesicles and bacterial cells also showed polymer-induced aggregation of both synthetic vesicles and bacterial cells. Isothermal titration calorimetry (ITC) afforded free energy of binding values (Delta G) and polymer to lipid binding ratios, plus revealed that the interaction is entropically favorable (Delta S>0, Delta H>0). It was observed that the strength of vesicle binding was similar between the active polymers while the binding stoichiometries were dramatically different.     

Oxidation of phenothiazine dyes by manganese(III) in sulfuric acid solution

Manganese(III) sulfato complexes cause the oxidative degradation of methylene blue and its partially and fully N-demethylated derivatives, azure B and thionine dyes, respectively, in sulfuric acid media. The reaction proceeds through a colored reactive organic radical generated in the first stage via one-electron oxidation of the starting material, leading to a mixture of N-demethylated and/or deaminated species. The rates of formation of the methylene blue and azure B radicals are much higher than those of their further decomposition, whereas the generation of the thionine radical is much slower than its immeasurably fast decay. The kinetics of decomposition of all three dyes and the methylene blue and azure B radicals were studied spectrophotometrically under isolation conditions at 298 K. The first stage of each reaction proceeds according to a second-order rate expression, being first order in the dyes and in the manganese(III) concentrations. Dependence of the pseudo-first-order rate constants on the oxidant concentration for the second stage exhibits a saturation effect under the applied conditions. It is postulated that electron transfer takes place between the [Mn(SO₄)₃]³⁻ complex and the protonated form of the dye. The reactivity order of the dyes as determined from the second-order rate constants for the first reaction stage corresponds to the order of their HOMO energies.     

Preparation and characterization of new mouldable cellulose-AESO biocomposites

A new concept of using acrylated epoxidized soybean oil (AESO) in the production of 3D cellulose biocomposites was evaluated. Cellulose-AESO composites were prepared by dissolving pulp in N,N-dimethylacetamide/lithium chloride and adding AESO and an initiator to the solutions followed by thermal curing and compression moulding at room temperature. The resulting biocomposites were characterized by FE-SEM, FT-IR, XRD, GC, TGA and nano- and microindentation. SEM images indicated the presence of spherical morphology and FT-IR together with TGA results showed no hydrogen or covalent bonding between the two components. The existence of hydrophobic interactions between AESO molecules and cellulose hydrophobic domains was proposed. AESO aggregates captured and covered by cellulose chains increase the flexibility of the composites acting as specific plasticizer and after polymerization introduce strength to the material. It was found that the optimal amount of AESO for achieving both desired hardness and good mouldability should be below 20 %.     

Phosphomimetic sulfonamide and sulfonamidoxy analogues of (Lyso)phosphatidic acid

Lysophosphatidic acid (LPA) and phosphatidic acid (PA) are potent bioactive lipid mediators of signal transduction and are inactivated by phosphatases. To obtain receptor-isoform selective ligands with neutral phosphomimetic head groups, we performed the stereoselective synthesis of LPA and PA analogues with trifluoromethanesulfonamide and trifluoromethanesulfonamidoxy moieties replacing the phosphomonoester.