Mechanical properties of liquid-filled shellac composite capsules

This paper describes the mechanical properties of thin-walled, liquid-filled composite capsules consisting of calcium pectinate and shellac. In a series of experiments we measured the deformation of these particles in a spinning drop apparatus. For different pH-values we studied the elastic properties of these particles and compared the obtained results with the mechanical response measured by squeezing capsule experiments. In analogy to these experiments, we also investigated liquid-filled unloaded calcium pectinate capsules without the addition of shellac. The deformation properties of these experiments and the surface Young moduli were in good agreement. Furthermore we investigated the liquid-filled calcium pectinate and the composite capsules by NMR microscopy. These experiments allowed investigations of the membrane thickness and the kinetics of membrane growing. Additional characterizations by stress controlled small amplitude surface shear experiments of similar composed gel layers provided coherent results for the surface Young modulus.     

Bis-phenanthroline copper(II) phthalate complexes are potent in vitro antitumour agents with 'self-activating' metallo-nuclease and DNA binding properties

Three, structurally characterised, bis-phen Cu(II) complexes of the phthalate isomers display rapid, low micromolar in vitro cytotoxicity against a range of epithelial tumour cells. The complexes induce relaxation of supercoiled plasmid DNA in the absence of external reducing agents and display efficient CT-DNA, Poly[d(A-T)](2) and Poly[d(G-C)](2) binding.     

Swarnalin and cis-swarnalin, two new tetrahydrofuran derivatives with free radical scavenging activity, from the aerial parts of Cuscuta reflexa

The reversed-phase HPLC analysis of a methanol extract of the aerial parts of Cuscuta reflexa afforded a non-separable mixture (55 : 45) of two novel tetrahydrofuran derivatives, named swarnalin (1) and cis-swarnalin (2), and a known coumarin, 5,6,7-trimethoxycoumarin (3). The structures of the compounds were elucidated unequivocally by UV, HRFABMS and a series of 1D and 2D NMR analyses. The mixture of 1 and 2 showed significant free radical scavenging activity in the DPPH assay and the RC50 value was found to be 3.80 x 10(-4) mg mL(-1) for the mixture, compared to 2.88 x 10(-5) mg mL(-1) for the positive control, quercetin.     

Validated MALDI-TOF/TOF mass spectra for protein standards

A current focus of proteomics research is the establishment of acceptable confidence measures in the assignment of protein identifications in an unknown sample. Development of new algorithmic approaches would greatly benefit from a standard reference set of spectra for known proteins for the purpose of testing and training. Here we describe an openly available library of mass spectra generated on an ABI 4700 MALDI TOF/TOF from 246 known, individually purified and trypsin-digested protein samples. The initial full release of the Aurum Dataset includes gel images, peak lists, spectra, search result files, decoy database analysis files, FASTA file of protein sequences, manual curation, and summary pages describing protein coverage and peptides matched by MS/MS followed by decoy database analysis using Mascot, Sequest, and X!Tandem. The data are publicly available for use at ProteomeCommons.org.     

Comparison of available analytical methods to measure trans-octadecenoic acid isomeric profile and content by gas-liquid chromatography in milk fat

Accurate quantification of trans-fatty acids (TFAs) could be achieved by infrared spectroscopy or by gas-liquid chromatography (GLC). Accurate quantification by GLC should be achieved using specific highly polar capillary columns such as 100 m CP-Sil 88 or equivalent. A pre-fractionation of cis and trans-fatty acids could be performed by silver-ion thin-layer chromatography (Ag-TLC), silver-ion solid-phase extraction (Ag-SPE), or by high-performance liquid-chromatography (HPLC). A pre-fractionation step allows accurate determination of the isomeric profile but it is not essential to achieve quantification of total trans-18:1 isomers nor to determine the level of vaccenic (trans-11 18:1) acid in dairy fat. TFA content could also be calculated in milk fat based on the TAG profile determined by GLC. In this paper, different GLC methods suitable to measure the total of trans-18:1 isomers, vaccenic acid and trans-18:1 acid isomeric distribution in milk fat were compared. Pre-separation of cis- and trans-18:1 isomers by Ag-TLC followed by GLC analysis under optimal conditions was selected as the reference method. Results obtained using alternative methods including pre-separation by HPLC followed by GLC analysis, direct quantification by GLC or calculation from the triacylglycerol (TAG) profile were compared to data acquired using the reference method. Results showed that accurate quantification of total trans-18:1 isomers and vaccenic acid could be achieved by direct quantification by GLC under optimal chromatographic conditions. This method represents a very good alternative to Ag-TLC followed by GLC analysis. On the other hand, we showed that pre-fractionation of fatty acid methyl esters (FAMEs) by HPLC represents a good alternative to Ag-TLC, even if some minor isomers are not selectively purified using this procedure.     

Protein adhesion on silicon-supported hyperbranched poly(ethylene glycol) and poly(allylamine) thin films

Hyperbranching poly(allylamine) (PAAm) and poly(ethylene glycol) (PEG) on silicon and its effect on protein adhesion was investigated. Hyperbranching involves sequential grafting of polymers on a surface with one of the components having multiple reactive sites. In this research, PAAm provided multiple amines for grafting PEG diacrylate. Current methodologies for generating PEG surfaces include PEG-silane monolayers or polymerized PEG networks. Hyperbranching combines the nanoscale thickness of monolayers with the surface coverage afforded by polymerization. A multistep approach was used to generate the silicon-supported hyperbranched polymers. The silicon wafer surface was initially modified with a vinyl silane followed by oxidation of the terminal vinyl group to present an acid function. Carbodiimide activation of the surface carboxyl group allowed for coupling to PAAm amines to form the first polymer layer. The polymers were hyperbranched by grafting alternating PEG and PAAm layers to the surface using Michael addition chemistry. The alternating polymers were grafted up to six total layers. The substrates remained hydrophilic after each modification. Static contact angles for PAAm (32-44 degrees) and PEG (33-37 degrees) were characteristic of the corresponding individual polymer (30-50 degrees for allylamine, 34-42 degrees for PEG). Roughness values varied from approximately 1 to 8 nm, but had no apparent affect on protein adhesion. Modifications terminating with a PEG layer reduced bovine serum albumin adhesion to the surface by approximately 80% as determined by ELISA and radiolabel binding studies. The hyperbranched PAAm and PEG surfaces described in this paper are nanometer-scale, multilayer films capable of reducing protein adhesion.     

Synthesis and properties of Q‐silicon crosslinked siloxane networks: H3PO4‐catalyzed sol–gel dehydration/crosslinking of α,ω‐bis(hydroxy)oligodimethylsiloxanes with tetrakis(hydroxydimethylsiloxy)silane

Six silicate‐crosslinked oligodimethylsiloxane thin films were prepared by the phosphoric acid (1 mol %) catalyzed condensation of α,ω‐bis(hydroxy)oligodimethylsiloxane (P) and tetrakis(hydroxydimethylsiloxy)silane (Q). Other acid catalysts were evaluated. P and Q were prepared by the Pd‐catalyzed oxidation of the corresponding Si? H compounds with water. The starting materials were characterized by IR and ¹H, ¹³C, and ²⁹Si NMR. A thermal cure was achieved with H₃PO₄ in 24 h and with poly(phosphoric acid) in 3 h at 110–120 °C. Dynamic mechanical analysis was used to determine the glass‐transition temperatures and to evaluate the mechanical properties of the films. Their thermal stabilities (≥300 °C) in air and N₂ were determined by thermogravimetric analysis. Small amounts of non‐crosslinked P were recovered from the films by Soxhlet extractions with CH₂Cl₂ and analyzed by IR, gel permeation chromatography, and ²⁹Si NMR. The crosslink densities were evaluated by the CH₂Cl₂ absorption capacities of the films. The surface properties of the films were determined by static and dynamic contact‐angle measurements. Electrochemical impedance spectroscopy was carried out to evaluate the corrosion‐protective properties of the coatings on mild steel as a function of the exposure time to 0.5 N NaCl. The biofoul‐release properties of the films were evaluated with sporelings from mature Ulva linza plants and barnacles. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2237–2247, 2006     

Modal Distribution Analysis, Synthesis, and Perception of a Soprano''s Sung Vowels

A high-resolution time-frequency analysis technique, the modal distribution, is applied to sung vowels from a soprano singer. Parameters are estimated for each partial component of notes analyzed with the modal distribution. These estimates are used in an additive synthesis model to generate replicates of the original recording, using a series of time-varying sinusoids. Additionally, a source-filter model is applied to create synthetic signals, where pitch- and vowel-specific filters and driving functions are constructed from the amplitude and frequency estimates obtained. Different driving functions, which sample the range of this singer's rate and excursion variation, are transposed and filtered to create synthetic signals. The perceptual salience of the different rates and excursions is then determined via a paired-comparison listening experiment. It is found that listeners are sensitive to small variations in both average vibrato rate and average vibrato excursion. However, the perceived amount of vibrato excursion varies somewhat depending upon the pitch at which the vibrato is “played” synthetically. Finally, the naturalness and sound quality of these synthetic examples is determined through both paired-comparison and single-note sound quality scaling listening experiments.