Calix[6]arene mono-diazonium salt synthesis and covalent immobilization onto glassy carbon electrodes

This Letter describes the fast synthesis of a mono-aminated calix[6]arene. The immobilization of this macrocycle onto glassy carbon electrodes via diazonium salt chemistry and the electrochemical characterization of the grafted organic layer are also reported.     

Stabilisation of 2,6‐Diarylpyridinium Cation by Through‐Space Polar–π Interactions

The through‐space polar–π interactions between pyridinium ion and the adjacent aromatic rings in 2,6‐diarylpyridines affect the pK_a values. Hammett analysis illustrates that the basicity of pyridines correlates well with the sigma values of the substituents at the para position of the flanking aryl rings.     

Quantification of Saquinavir from Lysates of Peripheral Blood Mononuclear Cells Using Microarrays and Standard MALDI-TOF-MS

Drug monitoring is usually performed by liquid chromatography coupled with optical detection or electrospray ionization mass spectrometry. More recently, matrix-assisted laser desorption/ionization (MALDI) in combination with triple quadrupole or Fourier-transform (FT) mass analyzers has also been reported to allow accurate quantification. Here, we present a strategy that employs standard MALDI time-of-flight (TOF) mass spectrometry (MS) for the sensitive and accurate quantification of saquinavir from an extract of blood peripheral mononuclear cells. Unambiguous identification of saquinavir in the mass spectra was possible because of using internal mass calibration and by an overall low chemical noise in the low mass range. Exact mass determination of the constant background peaks of the cell extract, which were used for recalibration, was performed by an initial MALDI-FT-MS analysis. Fast and multiplexed sample analysis was enabled by microarray technology, which provided 10 replicates in the lower nL range for each sample in parallel lanes on a chip. In order to validate the method, we employed various statistical tests, such as confidence intervals for linear regressions, three quality control samples, and inverse confidence limits of the estimated concentration ratios.

Evaluation of matrix‐assisted laser desorption/ionization (MALDI) preparation techniques for surface characterization of intact Fusarium spores by MALDI linear time‐of‐flight mass spectrometry

Unambiguous identification of mycotoxin‐producing fungal species as Fusarium is of great relevance to agriculture and the food‐producing industry as well as in medicine. Protein profiles of intact fungal spores, such as Penicillium, Aspergillus and Trichoderma, derived from matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) were shown to provide a rapid and straightforward method for species identification and characterization. In this study, we applied this approach to five different Fusarium spp. strains which are known to affect the growth of different grain plants. To obtain a suitable MALDI matrix system and sample preparation method, thin‐layer, dried‐droplet and sandwich methods and several MALDI matrices, namely CHCA, DHB, FA, SA and THAP dissolved in various solvent mixtures (organic solvents such as ACN, MeOH, EtOH and iPrOH and for the aqueous phase water and 0.1% TFA), were evaluated in terms of mass spectrometric pattern and signal intensities. The most significant peptide/protein profiles were obtained with 10 mg ferulic acid (FA) in 1 mL ACN/0.1% TFA (7:3, v/v) used as matrix system. Mixing the spores with the matrix solution directly on the MALDI target (dried‐droplet technique) resulted in an evenly distributed spores/matrix crystal layer, yielding highly reproducible peptide/protein profiles from the spore surfaces. Numerous abundant ions throughout the investigated m/z range (m/z 1500–15 000) could be detected. Differences in the obtained mass spectral patterns allowed the differentiation of spores of various Fusarium species. Copyright © 2009 John Wiley & Sons, Ltd.     

Modal theory for the two-frequency mutual coherence function in random media: beam waves

Pulse propagation in a random medium is mainly determined by the two-frequency mutual coherence function which satisfies the parabolic equation. It has recently been shown that this equation can be solved by separation of variables, thereby reducing the solution for any structure function to the solution of ordinary differential equations. In this paper, the method is applied for a beam-wave excitation in a random medium. The exact solution for a quadratic medium is derived. For non-quadratic power-law media an analytical expression at equal positions is presented.     

Synthesis and characterization of polyurethane ionomers with trimellitic anhydride and dimethylol propionic acid for waterborne self‐emulsifying dispersions

A new synthesis for polyurethane dispersions was developed using both trimellitic anhydride alone and in combination with dimethylol propionic acid as internal emulsifiers. During synthesis of the polyurethane ionomer, Fourier transform infrared spectroscopy was used for monitoring and characterizing both the polyaddition step and the anhydride ring opening process. Depending on the synthesis route, the carboxylic groups are either located at the end of the polymer backbone or additionally statistically distributed within the polymer chain itself. The effect of the carboxylic group's position on the chemical and physical properties, with particular reference to particle size and pH, was analyzed. Three different polyols were used to synthesize the polyurethane dispersions. Driven by the current trend to find renewable alternatives to petrochemical‐based raw materials, one bio‐based polyol was included for the synthesis. The effect of the different structures of the polyurethane dispersions (petrochemical‐ or bio‐based polyols) on mechanical properties and thermal behavior was investigated. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 680–690     

Spin‐labeling of polymeric micelles and application in probing micelle swelling using EPR spectroscopy

Polymer structure and conformational dynamics are essential to polymer macroscopic properties, but are challenging to probe. We report here a synthetic pathway to chemically add a nitroxide moiety onto block polymers in a mild, aqueous environment and demonstrate its use in a series of polymeric micelles using Electron Paramagnetic Resonance (EPR) spectroscopy. The micelles were characterized with several analytical approaches and EPR findings were in general consistent with other approaches. Upon exposure to organic solvents, the line shape changes reflected the micelle swelling and EPR spectral simulations revealed structural information of the swelled micelles. The label introduced via our method can be cleaved and replaced with other probes to report different information site‐specifically. The mild conditions facilitate the future use of EPR in solving biopolymer problems. In combination with other labeling approaches, one can perform polymer spin labeling with different chemistry, so that various information about polymers can be obtained site‐specifically. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017 , 55, 1770–1782     

Quantitative determination of alkannins and shikonins in endemic Mediterranean Alkanna species

The optical antipodes alkannin/shikonin (A/S) and their esters are potent pharmaceutical substances found in the roots of 150 Boraginaceous species. This study estimated and compared total and free A/S content and A/S enantiomeric ratio in roots of 11 Alkanna species (A. corcyrensis, A. tinctoria, A. pindicola, A. orientalis, A. methanaea, A. calliensis, A. graeca, A. primuliflora, A. stribrnyi, A. sieberi and A. noneiformis) growing wild in various Greek regions, to compare with cultivated species. It also re‐characterized the chirality of A/S commercial samples, since most of them were misnamed by the providers. Several Alkanna species were collected (groups 1 and 3) and botanically identified, whereas some Alkanna species were cultivated from collected seeds (group 2). Free A/S and derivatives were extracted from the dried roots of Alkanna species and analyzed by high performance liquid chromatography‐diode array detection (HPLC‐DAD). For total A/S content the hexane extracts of Alkanna roots were hydrolyzed and analyzed by HPLC‐DAD. Chirality determination and A/S enantiomeric ratio estimation was performed for several commercial samples by polarimetry,chiral LC‐DAD and circular dichroism studies. Quantitative analysis revealed that A/S content varied from one region to another even within the same species. Most of the cultivated samples contained greater amounts of free and total A/S compared with the wild ones, wheras no difference was observed in A/S enantiomeric ratio. All the Alkanna samples tested contain mainly alkannin derivatives. Some of the examined Alkanna species of the Greek flora that are endemic to the Mediterranean area could serve as alternative sources for medicinally valuable A/S derivatives. Most of the commercial A/S samples tested were misnamed in terms of chirality and re‐characterized. Copyright © 2013 John Wiley & Sons, Ltd.     

Development of a MALDI two-layer volume sample preparation technique for analysis of colored conidia spores of <Emphasis Type="Italic">Fusarium</Emphasis> by MALDI linear TOF mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI–TOF MS) has been proved to be a powerful tool for the identification and characterization of microorganisms based on their surface peptide/protein pattern. Because of the complexity of microorganisms, there are no standardized protocols to acquire reproducible peptide/protein profiles for a broad range of microorganisms and for fungi in particular. Small variations during MALDI MS sample preparation affect the quality of mass spectra quite often. In this study, we were aiming to develop a sample preparation method for the analysis of colored, a quite often observed phenomenon, and mycotoxin-producing Fusarium conidia spores using MALDI–TOF MS. Different washing solvent systems for light- and deep-colored (from slightly orange to red-brown) conidia spores and connected sample deposition techniques were evaluated based on MS reproducibility and number and intensities of peaks. As a method of choice for generation of reproducible and characteristic MALDI–TOF mass spectra, the use of a washing process for colored Fusarium conidia spores with acetonitrile/0.5% formic acid (7/3) was found and subsequently combined with two-layer volume technique (spores/matrix (ferulic acid) solution was deposited onto a MALDI target, and after solvent evaporation, a second matrix layer was deposited). With the application of this sample preparation method, for deep-colored Fusarium species, 19 abundant molecular ions in the m/z range 2,000–10,000 were always detected with an S/N ratio of 3:1 or better. Finally this optimized sample preparation for the first time provided mass spectrometric fingerprints of strongly colored Fusarium conidia spores resulting in the possibility of differentiation of such spores at the species level.