Separation of durum wheat proteins by ultrathin-layer isoelectric focusing: a new tool for the characterization and quantification of low molecular weight glutenins

An isoelectric focusing method capable of resolving all groups of storage protein of the wheat seed, including the most basic low molecular weight glutenin (LMWG), was developed. Ultrathin polyacrylamide gels were used after drying and rehydration with 8 M urea, 50 mM DTE and 2.4% carrier ampholytes (pH 4-9). Densitometric scanning of the isoelectric focusing gels permitted a more accurate and specific quantitation of LMWG components among various cultivars than patterns based on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The two main genetic types (i.e. 'gamma-42' and 'gamma-45') of durum wheats were separated on the basis of the proportion in LMWG in storage proteins, but no significant difference was found within these groups. Advantages of the system as regards reliability, high resolution, ability to abolish protein oxidation and preventing reaggregation of LMWG were also discussed.     

Dibenzopyrenes,other PAHs with molecular weight 302, and selected carcinogenic PAHs seldom determined: identification and one-year quantification in urban air

The unambiguous identification in environmental samples of the potent carcinogen dibenzo[a,l]pyrene (DBalP) and the other DBPs (DBaeP, DBaiP, DBahP), whose evidence of carcinogenicity was recently re-evaluated by the International Agency for Research on Cancer (IARC), is an analytical challenge. This is attributed to their low concentrations in the environment and to the co-presence of several 302?MW isomers. In this study the four DBPs were identified in air, together with further four isomers with MW 302, based on an overall evaluation of five acceptance criteria. Their annual mean concentrations were quantified, for the first time to our knowledge. Thirteen other isomers were tentatively identified by comparison with previously published gas chromatographic profiles. The determinations were performed on PM10 samples collected every sixth day at a site in Rome, solvent extracted and analysed using GC/LRMS. The primary objective was to determine the mean DBP concentrations the population may be exposed to, and their consequent carcinogenic risks relative to benzo[a]pyrene (BaP) taken as a reference polycyclic aromatic hydrocarbon (PAH). The mean concentrations of DBalP, DBaeP, DBaiP and DBahP were, respectively, 0.014, 0.07, 0.02 and 0.01?ng?m^?3 (BaP: 0.65?ng?m^?3). Based on the available toxicity equivalence factors, DBalP contributed the carcinogenic risk of the PAH mixture by a factor of 2 relative to the risk attributable to BaP. DBaeP, DBahP and DBaiP contributed by, respectively, 11%, 1% and 0.3% of BaP. The instrumental conditions used to determine the 302?MW isomers allowed to unambiguously identify and to quantify other PAHs, ‘possibly carcinogenic’ to humans according to IARC, whose atmospheric concentrations reported in literature are scarce or missing: benzo[c]phenanthrene, 5-methylchrysene and benzo[j]fluoranthene (the latter being baseline resolved from isomers b and k). Finally, for completeness of information on PAHs recently upgraded by IARC to ‘possibly carcinogenic’, the concentrations of cyclopenta[cd]pyrene are reported.     

A solid phase extraction procedure for the simultaneous determination of total inorganic arsenic and trace metals in seawater: Sample preparation for total-reflection X-ray fluorescence

In this paper we present a procedure allowing total-reflection X-ray fluorescence spectrometry (TXRF) determinations of arsenic in water samples, especially in seawater samples. The procedure consists of an arsenate reduction step (performed by using a l-cysteine solution) followed by a complexation of As⁺³ with sodium dibenzyldithiocarbamate and solid phase extraction. The new procedure is a modification of a method developed by Prange and allows a simultaneous determination of As together with V, Fe, Ni, Cu, Zn, Pb, and U in seawater by TXRF. The procedure was tested using the Certified Reference Material CASS-4 and was later applied to regular seawater samples collected from the North Sea. The detection limit for arsenic is 10 ng L^− 1.     

Syndiospecific polymerization of styrene in the presence of cyclic olefins: A new approach for molecular weight,molecular weight distribution,and stereoregularity controls for syndiotactic polystyrene

A new approach for facilitating microstructural controls for syndiotactic polystyrene (sPS), in which, styrene polymerization is conducted in the presence of cyclic olefins and hydrogen, is proposed. Detailed structural analyses revealed that cyclic olefins are not incorporated into the polystyrene main chain; instead, they are capable of interrupting the chain propagation processes by binding onto the active catalyst to form a cyclic‐olefin‐coordinated active site. Thus, in the presence of hydrogen, chain transfer by hydrogen addition occurs selectively, which leads to the generation of drastically lower molecular weight sPS with a narrower range of molecular weight distribution. Chain end structural analyses of the resulting polymers revealed that styrene polymerization under theses conditions involves a selective chain transfer pathway for providing styrene polymers with uniform chain end structures. A unique method for inducing a selective chain transfer reaction by using non‐incorporated cyclic olefins to regulate the chain reaction mechanism is demonstrated. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Novel ion chromatography technique for the rapid identification and quantification of saturated and unsaturated low molecular weight organic acids formed during the Fenton oxidation of organic pollutants

The Fenton oxidation process is one of the most widely used technologies in the oxidation of organic pollutants. The identification and quantification of end products of these oxidation processes is of prime importance due to environmental concerns of pollution and toxicity. In this work, we have developed a highly sensitive, cheap, easy and rapid method of determining low molecular weight mono and dicarboxylic acids using ion exclusion chromatography with inverse chemical suppression and conductivity detection. Eleven organic acids were simultaneously separated in 22min with detection limits ranging from 10 to 500ppb and limits of quantification from 0.05 to 50ppm. The method was tested and proved to be accurate, reproducible, precise and highly sensitive. Linearity was in the range of R2: 0.977-0.999, with a percentage error of less than 2% for oxalic and maleic acids, and less than 1% for the rest of the organic acids studied.     

High performance electrophoresis: A new method of continuous elution of electrophoretically separated high and low molecular weight compounds

Conclusions The purification of serum proteins is a precise and suitable test for the performance of an electrophoresis apparatus. The molecular weights and the isoelectric points of the various serum proteins cover a wide range. Consequently, the protein pattern observed after gel electrophoresis is very complex. Moreover, elution of the electrophoretically purified serum proteins is particularly complicated because some proteins such as albumin and transferrin appear as highly concentrated overloaded bands. If the elution method employed does not work extremely efficiently, residual quantities of albumin and transferrin, respectively, remain in the elution chamber and contaminate the following, slower protein zones. As Fig. 2 shows, no tailing of proteins can be observed in the pure fractions of this electrophoretic run, despite their high concentrations. Even in the case of proteins of low electrophoretic mobility in the late fractions, such as haptoglobins and immunoglobins, no dilution occurred.From these results it appears that the electrophoretic methods described provide a practical and highly efficient way of separating and analyzing high and low molecular weight ampholytes. Thus, technical aspects should no longer be the factor limiting realization of High Performance Electrophoresis.

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HPE: Eine neue Methode der kontinuierlichen Elution elektrophoretisch getrennter hoch- und niedrigmolekularer Verbindungen

     

A sensitive flow-batch system for on board determination of ultra-trace ammonium in seawater: Method development and shipboard application

Combining fluorescence detection with flow analysis and solid phase extraction (SPE), a highly sensitive and automatic flow system for measurement of ultra-trace ammonium in open ocean water was established. Determination was based on fluorescence detection of a typical product of o-phthaldialdehyde and ammonium. In this study, the fluorescence reaction product could be efficiently extracted onto an SPE cartridge (HLB, hydrophilic–lipophilic balance). The extracted fluorescence compounds were rapidly eluted with ethanol and directed into a flow cell for fluorescence detection. Compared with the common used fluorescence method, the proposed one offered the benefits of improved sensitivity, reduced reagent consumption, negligible salinity effect and lower cost. Experimental parameters were optimized using a univariate experimental design. Calibration curves, ranging from 1.67 to 300 nM, were obtained with different reaction times. The recoveries were between 89.5 and 96.5%, and the detection limits in land-based and shipboard laboratories were 0.7 and 1.2 nM, respectively. The relative standard deviation was 3.5% (n = 5) for an aged seawater sample spiked with 20 nM ammonium. Compared with the analytical results obtained using the indophenol blue method coupled to a long-path liquid waveguide capillary cell, the proposed method showed good agreement. The method had been applied on board during a South China Sea cruise in August 2012. A vertical profile of ammonium in the South East Asia Time-Series (SEATS, 18° N, 116° E) station was produced. The distribution of ammonium in the surface seawater of the Qiongdong upwelling in South China Sea is also presented.     

Photo-controlled diffusion in reacting liquid crystals: A new tool for the creation of complex molecular architectures

Diffusion enforced photo-assembling during polymerization of a chiralnematic monomer blend yields a cholesteric network in which the helical pitch gradually changes over the cross-section of the film. The polarization selective reflection band of cholesterics can be made much wider than those of single pitch materials and may expand over the whole visible wavelength. The paper discusses the photo-controlled diffusion process in thin films, the important process parameters and some of the properties of the molecular architectures obtained.     

Fe(NO3)3·9H2O/Fe(HSO4)3: An efficient reagent system for the oxidation of alcohols, thiols and sulfides in the absence of solvent

Fe(NO3)3·9H3O/Fe(HSO4)3 was used as an efficient reagent system for the oxidation of alcohols to their corresponding carbonylcompounds. All reactions were performed in the absence of solvent in good to high yields. Under the same reaction conditions,thiols and sulfides were also converted to their corresponding disulfides and sulfoxides, respectively.     

AGNES: A technique for determining the concentration of free metal ions. The case of Zn(II) in coastal Mediterranean seawater

Absence of Gradients and Nernstian Equilibrium Stripping (AGNES) is a recently suggested electroanalytical technique designed for the determination of the free concentration of heavy metals (such as Zn, Cd or Pb) which is here developed and applied to seawater samples. A key improvement for the implementation of AGNES with complex matrices is the development of a new blank, called the shifted blank (presented in this work for the first time), which can be applied to the same sample where the measurement is intended. The careful selection of the required parameters for the determination of the free Zn concentration (or activity) at the nanomolar level is described in detail. The methodology has been validated with a synthetic solution containing Zn and nitrilotriacetic acid (NTA) and then applied, as a first case, to two coastal seawater samples taken close to Barcelona and Tarragona (Catalonia, North-Eastern Spain) finding values in the range of 1-3 nM, representing around 25% of total Zn. This technique can, in the near future, be crucial in helping to elucidate the role of the free zinc(II) concentration in natural waters.     

Comparison of liquid-liquid extraction, solid-phase extraction and co-precipitation preconcentration methods for the determination of cadmium, copper, nickel, lead and zinc in seawater

Three major types of pre-concentration methods were evaluated and optimised for the extraction and determination of Cd, Cu, Ni, Pb and Zn from seawater samples. The traditional APDC/DDDC-Freon liquid-liquid extraction method showed excellent results for a multi-elemental analysis. However, the technique is labour consuming, very sensitive to operational conditions, employs environmentally unsafe and expensive solvents and requires large sample volumes. In the solid phase extraction method, the performances of a traditional Amberlite XAD-4 and a novel Dowex Optipore V-493 were evaluated. Application of Dowex Optipore V-493 resin provided better results at low concentrations than the generally used Amberlite XAD-4 resin using low sample volumes. However, the presence of natural organic compounds may decrease extraction efficiency of both resins for Cu. Thus, a pre-treatment with UV irradiation is advantageous for samples with high organic content. Cobalt co-precipitation methods showed good Cu and Ni recoveries, but gave poor results for Cd at low concentrations. In addition, high sample volumes are required. Both solid phase and co-precipitation methods showed unsatisfactory results in determination of Pb. Finally, a summary of methods advantages are given for choosing the most suitable method.     

Effect of the aging on lees and other alternative techniques on the low molecular weight phenols of Tempranillo red wine aged in oak barrels

The effect of different alternative techniques to the traditional aging on lees on the low molecular weight phenolic compounds of red wines was study as well as their evolution during the aging in oak wood barrels for six months. The study was carried out with Tempranillo red grapes from two consecutive vintages. The techniques assayed were the traditional aging on lees with or without the addition of exogenous β-glucanase enzymes, the use of yeast derivative preparations also with or without the addition of exogenous β-glucanase enzymes, the micro-oxygenation applied together with the aging on lees, and the use of non-toasted oak wood chips.     

A low molecular weight gel formed by cationic surfactant 1-dodecylpyridinium bromide in acetone/water: its characterisation and implication for enzyme immobilisation

A novel cationic surfactant-based gelling system is presented in this report. The cationic surfactant 1-dodecylpyridinium bromide (DPB) in the mixture of acetone and water can form gels without additive. The gel structure and the gelation mechanism were studied using techniques of rheology, microscopy, FT-IR and ¹H NMR spectroscopy. The present results indicate that the DPBs in acetone/water driven by hydrogen bonding, van der Waals force and other non-covalent interactions can self-assemble into rod-like fibers, and the fibers intertwined into a three-dimensional network. Laccase and horseradish peroxidase entrapped in the gel are biologically and/or electrochemically active. In addition, the present gel does not swell in the hydrophobic ionic liquid [Bmim]PF₆, showing its great promise in green biocatalysis and biotransformation.     

Polylaurylmethacrylate in bidimensional mixtures with low and high molecular weight substances: effect of the chain mobility on mutual miscibility

Bidimensional two-component mixtures of polylaurylmethacrylate with polyoctadecylmethacrylate, polymethylmethacrylate and stearic acid were studied in the 15–30 °C temperature range at the air-water interface, in order to determine the effect of the state of the hydrophobic side chains on the bidimensional miscibility.We showed that bidimensional miscibility depends on whether the two components have the same interfacial orientation, and that the fluidity of the polymer side chains also plays a very important role.     

A validated positive chemical ionization GC/MS method for the identification and quantification of amphetamine, opiates, cocaine, and metabolites in human postmortem brain

A sensitive and specific method for the simultaneous detection and quantification of amphetamine, opiates, and cocaine and metabolites in human postmortem brain was developed and validated. Analytes of interest included amphetamine, morphine, codeine, 6-acetylmorphine, cocaine, benzoylecgonine, ecgonine methyl ester, ecgonine ethyl ester, cocaethylene, and anhydroecgonine methyl ester. The method employed ultrasonic homogenization of brain tissue in pH 4.0 sodium acetate buffer and solid phase extraction. Extracts were derivatized with N-methyl-N-(tert-butyldimethylsilyl) trifluoroacetamide and N,O-bis(trimethylsilyl) trifluoroacetamide. Separation and quantification were accomplished on a bench-top positive chemical ionization capillary gas chromatograph/mass spectrometer with selected ion monitoring. Eight deuterated analogs were used as internal standards. Limits of quantification were 50 ng/g of brain. Calibration curves were linear to 1000 ng/g for anhydroecgonine methyl ester and 6-acetylmorphine, and to 2000 ng/g for all other analytes. Accuracy across the linear range of the assay ranged from 90.2 to 112.2%, and precision, as percent relative standard deviation, was less than 16.6%. Quantification of drug concentrations in brain is a useful research tool in neurobiology and in forensic and postmortem toxicology, identifying the type, relative magnitude, and recency of abused drug exposure. This method will be employed to quantify drug concentrations in human postmortem brain in support of basic and clinical research on the physiologic, biochemical, and behavioral effects of drugs in humans.     

Cost effective,robust, and reliable coupled separation techniques for the identification and quantification of phospholipids in complex biological matrices: Application to insects

The quantification of phospholipid classes and the determination of their molecular structures are crucial in physiological and medical studies. This paper's target analytes are cell membrane phospholipids, which play an important role in the seasonal acclimation processes of poikilothermic organisms. We introduce a set of simple and cost‐effective analytical methods that enable efficient characterization and quantification of particular phospholipid classes and the identification and relative distribution of the individual phospholipid species. The analytical approach involves solid‐phase extraction and high‐performance thin‐layer chromatography, which facilitate the separation of particular lipid classes. The obtained fractions are further transesterified to fatty acid methyl esters and subjected to gas chromatography coupled to flame ionization detection, which enables the determination of the position of double bonds. Phospholipid species separation is achieved by high‐performance liquid chromatography with mass spectrometry, which gives information about the headgroup moiety and attached fatty acids. The total content of each phospholipids class is assessed by phosphorus determination by UV spectrophotometry. The simultaneous analysis of phosphorus, fatty acid residues, and phospholipid species provides detailed information about phospholipid composition. Evaluation of these coupled methods was achieved by application to an insect model, Pyrrhocoris apterus. High correlation was observed between fatty acid compositions as determined by gas chromatography and high‐performance liquid chromatography analysis.     

A validated HPLC‐PDA method for identification and quantification of two bioactive alkaloids,ephedrine and cryptolepine,in different Sida species

A simple, rapid, accurate and reproducible reverse‐phase HPLC method has been developed for the identification and quantification of two alkaloids ephedrine and cryptolepine in different extracts of Sida species using photodiode array detection. Baseline separation of the two alkaloids was achieved on a Waters RP‐18 X‐terra column (250 × 4.6 mm, 5 µm) using a solvent system consisting of a mixture of water containing 0.1% Trifluoroacetic acid (TFA) and acetonitrile in a gradient elution mode with detection at 210 and 280 nm for ephedrine and cryptolepine, respectively. The calibration curves were linear in a concentration range of 10–250 µg/mL for both the alkaloids with correlation coefficient values >0.99. The limits of detection and quantification for ephedrine and cryptolepine were 5 and 10 µg/mL and 2.5 and 5 µg/mL, respectively. Relative standard deviation values for intra‐day and inter‐day precision were 1.22 and 1.04% for ephedrine and 1.71 and 2.06% for cryptolepine, respectively. Analytical recovery ranged from 92.46 to 103.95%. The developed HPLC method was applied to identify and quantify ephedrine and cryptolepine in different extracts of Sida species. Copyright © 2013 John Wiley & Sons, Ltd.     

A new method for precise determination of iron,zinc and cadmium stable isotope ratios in seawater by double-spike mass spectrometry

The study of Fe, Zn and Cd stable isotopes (δ⁵⁶Fe, δ⁶⁶Zn and δ¹¹⁴Cd) in seawater is a new field, which promises to elucidate the marine cycling of these bioactive trace metals. However, the analytical challenges posed by the low concentration of these metals in seawater has meant that previous studies have typically required large sample volumes, highly limiting data collection in the oceans. Here, we present the first simultaneous method for the determination of these three isotope systems in seawater, using Nobias PA-1 chelating resin to extract metals from seawater, purification by anion exchange chromatography, and analysis by double spike MC-ICPMS. This method is designed for use on only a single litre of seawater and has blanks of 0.3, 0.06 and <0.03 ng for Fe, Zn and Cd respectively, representing a 1–20 fold reduction in sample size and a 4–130 decrease in blank compared to previously reported methods. The procedure yields data with high precision for all three elements (typically 0.02–0.2‰; 1σ internal precision), allowing us to distinguish natural variability in the oceans, which spans 1–3‰ for all three isotope systems. Simultaneous extraction and purification of three metals makes this method ideal for high-resolution, large-scale endeavours such as the GEOTRACES program.     

Development and validation of an HPLC‐UV method for quantification of elvitegravir and two other new antiretrovirals,dolutegravir and rilpivirine,in the plasma of HIV‐positive patients

Therapeutic drug monitoring may be crucial in selected clinical conditions for the management of HIV infection. In recent years, new antiretrovirals have been introduced and in particular elvitegravir (EVG) is now recommended for first‐line and simplification treatment as well as dolutegravir (DTG) and rilpivirine (RPV). The aim of this study was to develop and validate a high‐performance liquid chromatography–ultraviolet (HPLC‐UV) method for determining EVG and new antiretrovirals DTG and RPV in human plasma. Solid‐phase extraction was applied to a 600 μL plasma sample. Chromatographic separation of the three drugs and internal standard was achieved with a gradient of acetonitrile and phosphate buffer on a C₁₈ reverse‐phase analytical column with a 20 min analytical run time. EVG and DTG were detected at 265 nm and RPV at 290 nm. Mean intra‐ and inter‐day precisions were < 10%; the mean accuracy was <15%. Extraction recovery ranged between 105 and 82% for the drugs analyzed. Calibration curves were optimized according to the expected ranges of drug concentrations in patients; the coefficient of determination was >0.997 for all drugs. This method allows for monitoring EVG, DTG and RPV in the plasma of HIV‐positive patients using HPLC‐UV.     

CAST: A new program package for the accurate characterization of large and flexible molecular systems

The presented program package, Conformational Analysis and Search Tool (CAST) allows the accurate treatment of large and flexible (macro) molecular systems. For the determination of thermally accessible minima CAST offers the newly developed TabuSearch algorithm, but algorithms such as Monte Carlo (MC), MC with minimization, and molecular dynamics are implemented as well. For the determination of reaction paths, CAST provides the PathOpt, the Nudge Elastic band, and the umbrella sampling approach. Access to free energies is possible through the free energy perturbation approach. Along with a number of standard force fields, a newly developed symmetry‐adapted perturbation theory‐based force field is included. Semiempirical computations are possible through DFTB+ and MOPAC interfaces. For calculations based on density functional theory, a Message Passing Interface (MPI) interface to the Graphics Processing Unit (GPU)‐accelerated TeraChem program is available. The program is available on request. © 2014 Wiley Periodicals, Inc.