Analysis of sulfated peptides from the skin secretion of the Pachymedusa dacnicolor frog using IMAC-Ga enrichment and high-resolution mass spectrometry

Immobilized metal ion affinity chromatography (IMAC) has been widely used for the enrichment of phosphopeptides, whereas no report exists describing the use of IMAC columns for the enrichment of sulfopeptides. In this study, we used IMAC-Ga microcolumns for the enrichment of sulfopeptides from a complex mixture of peptides, extracted from skin secretions of the Pachymedusa dacnicolor frog. The enriched fraction obtained by IMAC-Ga was analyzed by liquid chromatograpy/electrospray ionization mass spectrometry (LC/ESI-MS) in an Orbitrap XL and by matrix-assisted laser desorption/ionization time-of-flight time-of-flight (MALDI-TOF/TOF) in an ABI 4800 instrument. From this fraction, different sulfated and non-sulfated peptides belonging to the caerulin and bradykinin families were structurally characterized. Other interesting negatively charged groups, such as phosphate adducts of dermaseptins and pyridoxal phosphate attached to a protease inhibitor, were also characterized. Unexpectedly, some dermaseptin antimicrobial peptides were also enriched by IMAC-Ga and a Sauvatine-like peptide was also fully sequenced. Furthermore, neutral loss of sulfated peptides and their fragmentation patterns in the gas phase were also compared using collision-induced dissociation (CID) and high-energy collision dissociation (HCD). Our present study provides evidence that IMAC-Ga enrichment is a fast, useful and promising method for high-throughput analysis of sulfated-peptides, since high-resolution mass spectrometers can be used for this purpose.     

1‐(9H‐Carbazol‐4‐yloxy)‐3‐{[2‐(2‐methoxyphenoxy)ethyl]amino}propan‐2‐ol hemihydrate: a carvedilol solvatomorph

In the title racemic hemihydrated solvatomorph of carvedilol (carv), C₂₄H₂₆N₂O₄·0.5H₂O, the asymmetric unit contains two independent organic moieties and one water molecule. Within this 2(carv)·H₂O unit, the molecular components are strongly linked by hydrogen bonds and the unit acts as the basic building block for the crystal structure. Interactions parallel to (10) generate hydrogen‐bonded layers which are further linked by much weaker C—H...N/O interactions. The conformations of the organic molecules, as well as the hydrogen‐bonding interactions connecting them, are compared with other related structures in the literature.     

New Nematic Phase in Lyotropic Binary Liquid Crystals Detected by Positron Annihilation Techniquest

A new nematic phase in lyotropic binary liquid crystalline systems consisting of sodium dodecyl sulfate-water was detected, for the first time, in the absence of additives by utilizing positron annihilation techniques. Lyotropic and thermotropic phase transitions were also investigated by the same methods. The positron annihilation parameters have also indicated a better definition of the concentration ranges at which each phase exists in the system studied. Crossed polarized light microscopy was applied to substantiate these results.     

Local Volatility Pricing Models for Long-Dated FX Derivatives

Abstract

We study the local volatility function in the foreign exchange (FX) market, where both domestic and foreign interest rates are stochastic. This model is suitable to price long-dated FX derivatives. We derive the local volatility function and obtain several results that can be used for the calibration of this local volatility on the FX option's market. Then, we study an extension to obtain a more general volatility model and propose a calibration method for the local volatility associated with this model.     

A fully automated system for inorganic antimony preconcentration and speciation in urine

A study was undertaken to ascertain the analytical capabilities of l-methionine immobilized on controlled pore glass for Sb preconcentration and speciation. A fully automated on-line system, implemented with hydride generation (HG) and inductively coupled plasma optical emission spectrometry (ICP OES), was used. Sb(III), at pH 10 was selectively retained in the column containing the immobilized aminoacid, while Sb(V) was not retained at all. A 30% HCl solution was used as eluent agent. Prior to total Sb determination, a pre-reduction step with thiourea was necessary. An on-line pH adjusting and pre-reduction of Sb(V) was achieved in a fully automated system. The detection limit for the preconcentration of 10 mL of an aqueous solution was 70 ng L⁻¹ with a relative standard deviation of 2%. An enrichment factor of 20 was achieved when 10 mL of sample was passed through the system, reaching a throughput of 23 samples per hour. The method was successfully applied to the determination of Sb(III) and total Sb in urine.     

13C NMR determination of the microstructure of polypropylene obtained with the DADNi(NCS)2/methylaluminoxane catalyst system

A complete ¹³C NMR characterization of a polymer synthesized with a new Ni‐diimine complex [DADNi(NCS)₂, where DAD = 2,6‐iPr? C₆H₃? N?C(Me)? C(Me)? N? 2,6‐iPr? C₆H₃] activated by methylaluminoxane by homopolymerization of propylene is presented. The amorphous material was made up mainly of blocks of syndiotactic polypropylene and ethylene–propylene copolymer. Some degree of propylene inversion (<1.2 mol %) and of long isobutyl and 2‐methyl hexyl branching (<1 mol %) were assigned and quantified. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2171–2178, 2004     

Metal fractionation of atmospheric aerosols via sequential chemical extraction: a review

This review surveys schemes used to sequentially chemically fractionate metals and metalloids present in airborne particulate matter. It focuses mainly on sequential chemical fractionation schemes published over the last 15 years. These schemes have been classified into five main categories: (1) based on Tessiers procedure, (2) based on Chesters procedure, (3) based on Zatkas procedure, (4) based on BCR procedure, and (5) other procedures. The operational characteristics as well as the state of the art in metal fractionation of airborne particulate matter, fly ashes and workroom aerosols, in terms of applications, optimizations and innovations, are also described. Many references to other works in this area are provided.     

Trace elements content in size-classified volcanic ashes as determined by inductively coupled plasma-mass spectrometry

At present there is an increasing concern as regards the release of potentially toxic metals into the environment. Volcanic eruptions are a natural source of metals and metalloids in the atmosphere. Toxic trace elements ejected during an eruptive episode may produce hazardous effects for people and the environment in areas close to the volcano. In this context, a study was undertaken to investigate the concentration of metal and metalloids in ashes ejected from Copahue volcano, Neuquén, Argentina. Two samples (A and B) of deposited particles were collected one day after the first eruption and size-fractionated in four sub-samples (S1, S2, S3 and S4). Analysis was performed by inductively coupled plasma-mass spectrometry (ICP-MS) and the accuracy for the entire analytical procedure was performed by means of the certified reference material CRM GBW 07105 Rocks (NRCCRM, China). The elements considered were: As, Cd, Cr, Cu, Hg, Ni, Pb, Sb, U, V and Zn. The adverse effect of potentially interfering species on the mass-spectrometric determination of these elements was also taken into account. The concentration intervals found in the four fractions are as follows (in μg g⁻¹): As, 6.0-2.6; Cd, 0.71-0.36; Cr, 29.5-54.0; Cu, 132-49.0; Hg, 0.020-0.007; Ni, 36.0-26.0; Pb, 15.5-2.55; Sb, 1.07-0.30; U, 2.57-1.94; V, 152-106; Zn, 85.5-55.0. The elements with the highest concentrations were: Cu, V and Zn. All fractions, in both samples, were found to be enriched in some toxic trace elements in the following order Sb>Cd>As. On the contrary, samples were depleted in Ni, Cr and Hg. Lead was the element that exhibits a noticeable difference in concentration between the finer and coarser fractions.