Functional Binding Surface of a β‐Hairpin VEGF Receptor Targeting Peptide Determined by NMR Spectroscopy in Living Cells

In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast ¹⁵N‐edited NMR spectroscopic experiments. To this aim, ¹⁵N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope‐edited NMR spectroscopic experiments, including ¹⁵N relaxation measurements, allowed a precise characterization of the in‐cell HPLW epitope recognized by VEGFR2.     

Synthesis and gas barrier characterization of poly(ethylene isophthalate)

Poly(ethylene isophthalate) (PEI) was synthesized for this research with essentially a condensation polymerization of isophthalic acid and ethylene glycol catalyzed by zinc acetate and antimony trioxide. Several samples were obtained, and their characteristics were observed and compared with poly(ethylene terephthalate) (PET). The synthesized PEI samples were chemically identified by ¹H NMR. Thermal analysis with differential scanning calorimetry (DSC) yielded results that indicate the samples were primarily amorphous, with a glass‐transition temperature of 55–60 °C. Molecular weights of these PEI samples were also obtained through intrinsic viscosity measurements (Mark–Houwink equation). Molecular weights varied with conditions of the polymerization, and the highest molecular weight achieved was 21,000 g/mol. Finally, the diffusion coefficient, solubility, and permeability of CO₂ gas in PEI were measured and found to be substantially lower than in PET, as anticipated from their isomeric chemical structures. This is because in PET the phenyl rings are substituted in the para (1,4) positions, which allows for their facile flipping, effectively permitting gases to pass through. However, the meta‐substituted phenyl rings in PEI do not permit such ring flipping, and thus PEI may be more suitable for barrier applications. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 4247–4254, 2004     

Determination of climbazol in shampoos by reversed-phase liquid chromatography

A method based on ior-pair reversed-phase liquid chromatography is reported for the determination of climbazol, a preservative used in cosmetic products. The column was packed wit LiChrosob RP-18, the mobile phase was acetonitrile-sodium perchlorate (0.05 M, pH 3.0) (40 + 60) and detection was at 224 nm. The method was applied to the analysis of commercial shampoos. The detection limit was 10 ng injected and calibration linearity was observed up to 6 μg.     

Cu+(H2) and Na+(H2) adducts in exchanged ZSM-5 zeolites

Cu(I) ions in Cu-ZSM-5 form Cu+(H2) complexes, stable at room temperature and sub-atmospheric H2 pressure, which do not have any homogeneous analogue except for matrix-isolated [Cu(eta2-H2)Cl]. Comparison with the unstable Na+(H2) adducts formed in the parent Na-ZSM-5 zeolite allow the conclusion that the Cu(I)/H2 bond is governed by sigma-pi overlap forces.     

The dimensions of the alternating polyesteramide 6NT6

The Flory-Williams rotational isomeric state models describing the conformational characteristics of polyesters and polyamides are combined to calculate the dimensions of the alternating polyesteramide (PEA) of the type 6NT6. The calculated ratio of unperturbed dimensions $\text{(〈r}{}^2\text{〉}{}_{\mathrm{o}}\text{/M}\text{)}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ is $\text{1.03}\text{A}\text{?}\text{/gmole}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ in excellent agreement with the value $\text{1.00}\text{A}\text{?}\text{/gmole}{}^{\mathrm{<mtext>1</mtext><mtext>2</mtext>}}$ recently obtained from an intrinsic viscosity-molecular weight study of PEA.     

Fluoropolyethers end‐capped by polar functional groups. III. Kinetics of the reactions of hydroxy‐terminated fluoropolyethers and model fluorinated alcohols with cyclohexyl isocyanate catalyzed by organotin compounds

The kinetics of the dibutyltin dilaurate (DBTDL)‐catalyzed urethane formation reactions of cyclohexyl isocyanate (CHI) with model monofunctional fluorinated alcohols and fluoropolyether diol Z‐DOL H‐1000 of various molecular weights (100–1084 g mol^?1) in different solvents were studied. IR spectroscopy and chemical titration methods were used for measuring the rate of the total NCO disappearance at 30–60 °C. The effects of the reagents and DBTDL catalyst concentrations, the solvent and hydroxyl‐containing compound nature, and the temperature on the reaction rate and mechanism were investigated. Depending on the initial reagent concentration and solvent, the reactions could be well described by zero‐order, first‐order, second‐order, or more complex equations. The reaction mechanism, including the formation of intermediate ternary or binary complexes of reagents with the tin catalyst, could vary with the concentration and solvent and even during the reaction. The results were treated with a rate expression analogous to those used for enzymatic reactions. Under the explored conditions, the rate of the uncatalyzed reaction of fluorinated alcohols with CHI was negligible. Moreover, there was no allophanate formation, nor were there other side reactions, catalysis by urethane in the absence of DBTDL, or a synergetic effect in the presence of the tin catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3771–3795, 2002     

Extraction of humic acids from a natural matrix by alkaline pyrophosphate. Evaluation of the molecular weight of fractions obtained by ultrafiltration

 Fractions of humic acids, resolved by ultrafiltration of extracts from a sample of peat treated with alkaline pyrophosphate solution, have been submitted to high-performance size-exclusion chromatography, with the aim of determining the molecular weight distributions. Anomalous peaks, located at retention volumes higher than those corresponding to the main signal, are present in the elution profiles relative to the lightest fractions. These peaks are more intense when using a refractive index detector rather than a UV detector. Elemental analysis data for the lightest fractions suggested that the spurious peaks are due to the presence of inorganic material. The hypothesis that pyrophosphate interacts with humic acids in the course of the extraction has been confirmed by colorimetric determination of the phosphorus content in the different fractions. As a consequence, the extraction procedure has been modified by using 0.1 mol/L NaOH as extractant. The average molecular weights of the various fractions, following NaOH extraction, result in substantial agreement with those obtained following pyrophosphate solution extraction (if the ‘pyrophosphate peaks’ present in the chromatographic profile are discarded in the calculations). Received: 18 November 1996 / Revised: 18 February 1997 / Accepted: 23 February 1997     

Simple Extraction and HPLC Determination of UV-A and UV-B Filters in Sunscreen Products

The determination of 11 organic UV filters, worldwide authorised in sunscreen formulations, was performed by HPLC with UV spectrophotometric detection. The filters determined were: phenylbenzimidazole sulfonic acid, benzophenone-4, benzophenone-3, 4-methylbenzylidene camphor, ethylhexyl methoxycinnamate, octocrylene, methylene bis-benzotriazolyl tetramethylbutyl phenol, butyl methoxydibenzoylmethane, bis-ethylhexyloxyphenol methoxyphenyltriazine, ethylhexyl triazone, and diethylamino hydroxybenzoyl hexyl benzoate. Three analytical methods were developed which were based on an ultrasonic extraction of the sample in methanol/1% aqueous acetic acid (70:30, v/v) or dimethylacetamide/propan-2-ol (1:1, v/v) in dependence of the water or fat-solubility of the filter, followed by HPLC separation and quantitation. HPLC was carried out using three different columns and eluting conditions. Standard calibration curves were linear for all the analytes over the concentration range 0.5–100 μg mL^?1. UV measurements were carried out at 280, 300, 310 or 360 nm with the aid of a diode array detector in dependence on the maximum absorption of each filter. Quantitative recoveries were obtained for all sunscreen compounds determined in homemade formulations. The proposed analytical procedure has been successfully applied for the analysis of commercial samples in order to check the presence of UV filters and to determine their concentration.     

Determination of90Sr by thin layer radiochromatography

A simple method for the determination of⁹⁰Sr by using thin layer chromatography on silica gel or cellulose pretreated with calcium oxalate is proposed. In these conditions a complete separation between strontium and its daughter yttrium is obtained. Radioactivity of separated elements was measured by a linear multiscanner analyzer and the results were computer processed to obtain the activity of⁹⁰Sr. The method has been applied to samples of water and milk subjected to a very simple extraction procedure. Under the experimental conditions used, the detection limit is about 25 mBq of deposited radioactivity, which corresponds to about 6 Bq/l.