bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acrolein‐sequestering ability of endogenous dipeptides: characterization of carnosine and homocarnosine/acrolein adducts by electrospray ionization tandem mass spectrometry
Authors: Carini Marina , Aldini Giancarlo , Beretta Giangiacomo , Arlandini Emanuele , Facino Roberto Maffei 
Published: September 2003

AbstractAcrolein (ACR), the carbonyl toxin produced by lipid peroxidation, is significantly increased in Alzheimer's disease brain. Since ACR is one of the most reactive and neurotoxic aldehydes, and human brain contains both carnosine (β‐alanine‐L‐histidine) and homocarnosine (γ‐aminobutyryl‐L‐histidine), the aim of this work was first to evaluate the quenching ability of the two peptides towards ACR and then to characterize their reaction products by electrospray ionization tandem mass spectrometry (ESI‐MS/MS; infusion experiments; positive‐ion mode). The reaction progress of ACR with carnosine or homocarnosine was studied in phosphate buffer, by monitoring ACR consumption (by reverse‐phase LC) and formation of the reaction products by ESI‐MS/MS at different incubation times. N‐Acetylcarnosine was used as reference compound to identify the sites of reaction. Both the dipeptides were able to quench ACR by almost 60% at 1 h and by more than 85% after 3 h incubation. Different reaction products between ACR and carnosine/homocarnosine were detected after 3 and 24 h, to indicate a complex reaction pathway involving sequential addition of 1, 2 and 3 moles of ACR/mole of the dipeptide to both the β‐alanine and histidine residues. The ESI mass spectra of ACR/carnosine reaction mixtures indicate formation of several molecular species, among which the predominant are: (a) the 14‐membered macrocyclic derivatives, deriving from the formation of the iminic bond between the terminal amino group followed by intramolecular Michael addition of the C(3) of the ACR moiety to histidine; (b) the Nβ‐(3‐formyl‐3,4‐dehydropiperidino) derivatives arising from the Michael addition of two acrolein molecules to the amino group of β‐alanine, followed by an aldol condensation and dehydration.The reaction of homocarnosine with ACR follows the same pathway, giving rise to the formation of homologous adducts. The results of this study shed light on the mechanism, until now never demonstrated, through which carnosine and homocarnosine detoxify the highly reactive aldehyde acrolein in a buffer system, and represent the starting point for further studies aimed at elucidating the biological role of these dipeptides in brain. Copyright © 2003 John Wiley & Sons, Ltd.
Determination of estrogens and progestogens by mass spectrometric techniques (GC/MS, LC/MS and LC/MS/MS)
Authors: Díaz‐Cruz M. Silvia , López de Alda María J. , López Ramón , Barceló Damià 
Published: September 2003

AbstractSteroid sex hormones and related synthetic compounds have been shown to provoke alarming estrogenic effects in aquatic organisms, such as feminization, at very low concentrations (ng/L or pg/L). In this work, different chromatographic techniques, namely, gas chromatography/mass spectrometry (GC/MS), liquid chromatography/mass spectrometry (LC/MS) and liquid chromatography/tandem mass spectrometry (LC/MS/MS), are discussed for the analysis of estrogens, both free and conjugated, and progestogens, and the sensitivities achieved with the various techniques are inter‐compared. GC/MS analyses are usually carried out after derivatization of the analytes with bis(trimethylsilyl)trifluoroacetamide (BSTFA). For LC/MS and LC/MS/MS analyses, different instruments, ionization techniques (electrospray (ESI) and atmospheric pressure chemical ionization (APCI)), ionization modes (negative ion (NI) and positive ion (PI)) and monitoring modes (selected ion monitoring (SIM) and selected reaction monitoring (SRM)) are generally employed. Based on sensitivity and selectivity, LC/ESI‐MS/MS is generally the method of choice for determination of estrogens in the NI mode and of progestogens in the PI mode (instrumental detection limits (IDLs) 0.1–10 ng/mL). IDLs achieved by LC/ESI‐MS in the SIM mode and by LC/ESI‐MS/MS in the SRM mode were, in general, comparable, although the selectivity of the latter is significantly higher and essential to avoid false positive determinations in the analysis of real samples. Conclusions and future perspectives are outlined. Copyright © 2003 John Wiley & Sons, Ltd.
Quantitative determination of UV filters in sunscreen lotions using microemulsion electrokinetic chromatography
Authors: Klampfl Christian W. , Leitner Tanja 
Published: September 2003

AbstractMicroemulsion electrokinetic chromatography (MEEKC) has been applied to the separation of some UV filters (Eusolex 4360, Eusolex 6300, Eusolex OCR, Eusolex 2292, Eusolex 6007, Eusolex 9020, Eusolex HMS, Eusolex OS, and Eusolex 232) commonly used in sunscreen lotions. Use of a MEEKC buffer with a mixed surfactant system to stabilize the oil droplets and an organic modifier in the aqueous phase allowed separation of most of the selected analytes in a single run in a system fitted with a diode array detector recording three wavelengths (240 nm, 300 nm, and 380 nm) simultaneously. The microemulsion employed consisted of 2.25 g of SDS, 0.75 g of Brij 35, 6.6 g 1‐butanol, 0.8 g n‐octane, 17.5 g 2‐propanol, and 72.1 g of 10 mM borate buffer (pH 9.2). Detection limits from 0.65 to 6.0 μg/mL were obtained and the calibration plots were linear over at least one order of magnitude for all analytes. The developed method could be applied to the determination of UV filters in several sun protection products including lotions, milks, and oils. Comparison of the obtained data with those from an HPLC method described in the literature showed acceptable agreement.
GC analysis of extractive compounds in beech wood
Authors: Zule Janja , Može Adolf 
Published: September 2003

AbstractVarious highly hydrophobic beech wood lipids were characterized and their quantities measured in hexane extracts by GC, using short and long capillary columns. More polar compounds were also identified in acetone extracts. Triglycerides, steryl esters, sterols, unsaturated fatty acids, as well as various monosaccharide units were determined as possible pollutants of papermaking systems.
Characterisation of interferon α‐2b by liquid chromatography and mass spectrometry techniques
Authors: Cindrić Mario , Vuletić Marko 
Published: September 2003

AbstractInterferon α‐2b produced by Escherichia coli consists of 165 amino acids and contains two disulphide bonds; its purity was confirmed by LC‐UV (DAD)‐FLD and LC‐MS techniques. A C4 column was used with UV detection at 214 nm; diode array detector (DAD) spectra were recorded from 200–400 nm and fluorescence detection was performed at specific wavelengths of trypthophan emission and excitation. Peptide mapping was performed with trypsin. Peptides produced by trypsin digestion were analysed by LC‐UV (DAD)‐FLD, LC‐MS, and LC‐MS/MS using a C18 column. Amino acid sequence coverage was about 95%. UV spectra in the range from 200 nm to 400 nm, emission (Em) and excitation (Ex) spectra of each separated peptide were additionally compared with spectra of the same peptide produced by digestion of European Pharmacopaeia interferon α‐2b standard (spectral matching). The chromatogram of any interferon α‐2b (drug substance or certificated standard) sample produced in the same manner with the same amino acid composition should be similar to the chromatogram obtained by the method described in this paper. Molecular masses of peptides were obtained from MS experiments and MS/MS experiments gave additional structural information. The molecular mass of interferon α‐2b was obtained by MALDI‐TOF MS analysis in linear mode, with an accuracy comparable to the theoretical average mass ± 5 atomic mass units. The molecular mass was obtained from the deconvoluted ESI mass spectrum.
Comparison of gas and high performance liquid chromatography with selective detection for determination of triazine herbicides and their degradation products extracted ultrasonically from soil
Authors: Stipičević Sanja , Fingler Sanja , Zupančič‐Kralj Lucija , Drevenkar Vlasta 
Published: September 2003

AbstractGC and HPLC with selective detectors were compared for simultaneous determination of triazine herbicides simazine, atrazine, propazine, terbuthylazine, cyanazine, ametryn, prometryn, and atraton, and of their dealkylated degradation products in soil. The compounds were ultrasonically extracted from spiked agricultural soil samples (organic matter content < 5%) with a 2:1 acetone:n‐hexane mixture. High efficiency of GC capillary column and high selectivity of the thermionic sensitive detector (TSD) and ion trap detector (ITD) made it possible to directly analyse uncleaned soil extracts and determine all 12 compounds in one run. In reversed‐phase HPLC with diode‐array detector (DAD), the co‐elution of soil matrix components interfered with the determination of methylthiotriazines and terbuthylazine. The recovery of triazine compounds, determined by GC‐TSD, from a silty sand soil (organic matter content 1.82%, pH 6.22) spiked at levels of 15–600 ng g–1, were 70–90% (RSD 9–19%), except for deisopropylatraton (38%). GC‐TSD analysis with detection limits of 5–15 ng g–1 for chloro‐ and methylthiotriazines and 30 ng g–1 for methoxytriazines was more sensitive than GC‐MS(ITD). GC analysis with electron capture detection was sensitive for some chlorotriazines, but a reliable compound quantification in complex chromatograms of uncleaned soil of extracts was not possible. For all compounds save didealkylatrazine, HPLC‐DAD was at least two times less sensitive than GC‐TSD. Soil/sediment organic matter, clay and silt content, and pH were identified as matrix characteristics which might affect ultrasonic extraction recovery of a particular compound.
Microwave‐assisted saponification for the determination of 16 polycyclic aromatic hydrocarbons from pumpkin seed oils
Authors: Gfrerer Marion , Lankmayr Ernst 
Published: September 2003

AbstractThe production of pumpkin seed oil requires a roasting of the pumpkin seeds, at temperatures generally higher than 60°C. The roasting at elevated temperatures produces the typical taste of the pumpkin seed oil but may also be the source of a contamination with carcinogenic PAHs. Owing to their lipophilic character, their bioaccumulation, and their toxicity these compounds should be subject to mandatory monitoring. Since there is a lack of norms and legal limits for hot‐pressed oils, the limits set by the German Society of Fat Science of 25 μg/kg for the sum of 16 PAHs and 5 μg/kg for the heavy fraction for refined and cold‐pressed oils, such as olive oil and others, have to be applied. Sample preparation was performed by microwave‐assisted saponification with 1.5 M methanolic potassium hydroxide followed by a liquid‐liquid extraction and purification with sulfuric acid. A final clean up procedure was performed on activated silica gel combined with a preparative Bondesil‐cyano phase. For a selective measurement of the individual analytes, gas chromatography combined with mass spectroscopy was used in single ion monitoring mode. The overall analytical procedure was validated by systematic recovery experiments and by analyzing the certified reference material BCR CRM 458. Finally, this validated method was used for quality control of pumpkin seed oils from a producer co‐operative.
Separation of isomers of dienoic acids by electromigration techniques
Authors: Cigić Irena Kralj , Guček Marjan , Zupančič‐Kralj Lucija , Pihlar Boris 
Published: September 2003

AbstractDifferent capillary electromigration techniques were employed to resolve geometrical isomers of sorbic acid, decadienoic acid, and ethyl sorbate. Since these substances differ in their polarity, shape, and size, various electromigration approaches were investigated to separate the four geometrical isomers of each compound. With capillary electrophoresis (CE) modified with a cyclodextrin (β‐CD) the four isomers of sorbic acid were separated using a buffer that consists of 60 mM tetraborate and 8 mg/mL β‐CD. The separation of decadienoic acid geometrical isomers was not possible, even at elevated tetraborate and cyclodextrin concentrations. The four isomers of decadienoic acid were successfully separated using micellar electrokinetic chromatography (MEKC) with a buffer consisting of 30 mM tetraborate and 100 mM SDS and microemulsion electrokinetic chromatography (MEEKC). Ethyl sorbate is the least polar of all the studied substances and its isomers could not be separated by MEKC or MEEKC. The resolution was improved and isomers were fully separated using capillary electrochromatography (CEC) with ODS stationary phase and a mobile phase consisting of 10 mM boric acid in 50% acetonitrile. Minor differences in the polarity and the shape of isomers and high resolving power of the applied techniques were sufficient for separation of very similar compounds. We have shown that versatile electromigration techniques can be applied for separation of geometrical isomers of dienoic acids and their esters.
HPLC‐DAD in identification and quantification of selected coumarins in crude extracts from plant cultures of Ammi majus and Ruta graveolens
Authors: Kamiński Marian , Kartanowicz Rafał , Kamiński Marcin M. , Królicka Aleksandra , Sidwa‐Gorycka Matylda , Łojkowska Ewa , Gorzeń Wojciech 
Published: September 2003

AbstractThis paper describes a method for the separation and determination of selected coumarins and furanocoumarins in the crude extracts from plant tissue cultures of Ammi majus hairy roots and Ruta graveolens cell suspensions, cultured in vitro, separately or together as co‐cultures. The usefulness of the three main components of the eluent used in reversed‐phase high performance liquid chromatographic analysis, namely: methanol (MeOH), acetonitrile (ACN), and tetrahydrofuran (THF), and different elution programs, was assessed. In the optimal analytical method a Lichrospher® RP‐18e 5‐μm column, a THF‐MeOH elution gradient, and a UV/VIS DAD detector were used. Due to the presence of many different compounds in the investigated plant extracts, the use of a UV/VIS DAD detector was essential. Coumarins were identified by comparison of their UV spectra with those of the analytical standards, and characterization of peak purity.
Isolation and determination of carbendazim residue from wheat grain by matrix solid‐phase dispersion and HPLC
Authors: Michel Monika , Buszewski Bogusław 
Published: September 2003

AbstractCarbendazim residues were analyzed by column‐switching high‐performance liquid chromatography (HPLC) with photodiode array detection (PDA). The active ingredient was extracted by matrix solid‐phase dispersion (MSPD) from wheat grain on an acidic silica gel column using a methanol‐dichloromethane mixture. The recovery rate for fortified samples was 87.3 ± 3.3% with a standard deviation (SD) of 2.9%. The detection limit was 0.02 μg/mL. The method was applied to the determination of carbendazim residues in wheat grain samples from a treated field.
A comparative study of hydrophobicity of octadecyl and alkylamide bonded phases based on methylene selectivity
Authors: Gadzała‐Kopciuch Renata , Buszewski Bogusaław 
Published: September 2003

AbstractThe conformational dynamics of home‐made monomeric and polymeric (octadecyl – C18 and alkylamide – AP) stationary phases have been investigated by analyzing the dependence of retention on the reciprocal temperature for different organic compounds. Theoretical considerations were based on the results of methylene selectivity determination. Two selected PAHs – naphthacene and benzo[a]anthracene, whose structures differ in the position of the ring – were chosen as solutes to study the thermodynamics of retention behavior. Standard enthalpies (ΔH 0) were obtained from the slope of the plots of the capacity factor logarithm (ln k) against the reciprocal temperature (1/T), i. e. van't Hoff plots, in a temperature range from 285 to 315 K. The conformation of the stationary phase (monomeric and polymeric) structure and the length of bonded ligands with their specific functional (N‐acylamide) groups had a significant effect on retention.
New method for bonding an adsorbent film to the walls of capillary columns
Authors: Wawrzyniak Rafał , Wasiak Wiesław 
Published: September 2003

AbstractA new method for immobilisation of an adsorbent on the wall of a capillary column ensures high thermal and mechanical stability of the resulting coating. The method can be applied to a variety of adsorbents of natural or synthetic origin. Its effectiveness is illustrated by results obtained for coating with modified silica or molecular sieve 13X.
Determination of benzene, toluene, ethylbenzene, and xylenes in urine by purge and trap gas chromatography
Authors: Brčić Irena , Skender Ljiljana 
Published: September 2003

AbstractA method for determination of benzene, toluene, ethylbenzene, and xylenes (BTEX) in urine is described. Determination is performed by dynamic headspace (purge and trap) gas chromatography with photoionization detection. The features of the described method, i.e. detection limits of 15–35 ng L–1, relative standard deviations of 0.2–10%, accuracy of 80–100%, removal of interference of many compounds present in urine, sharp chromatographic peaks because of cryogenic refocusing, no sample preparation, make it convenient for biological monitoring of exposure to low levels of BTEX. However, the method is time‐consuming and sophisticated.
Purification of peanut proteins for further use in affinity chromatography and as immunogens
Authors: Baumgartner Sabine , Hemetsberger Claudia , Drs Elisabeth , Pichler Harald , Krska Rudolf 
Published: September 2003

AbstractChickens were immunised with peanut protein extracts. Because of the high cross reactivity, the lgY antibodies were purified by means of an affinity column. An ion chromatographically purified peanut protein fraction was therefore coupled to the affinity support material and this column was used for further lgY purification.
Increased Resolution of Macromolecules with Agarose Gel Electrophoresis Compared with Polyacrylamide Gel Electrophoresis
Authors: Aksoy Nurten , Unlu Sebnem 
Published: September 2003

AbstractPolyacrylamide gel electrophoresis (PAGE) is routinely used for electrophoretic characterization of biomolecules. In this study we demonstrate that this technique is quite useful for the characterization of small molecules, however, it becomes inadequate for the resolution of high‐molecular‐weight macromolecules like MUC2 mucins. We show that agarose gel electrophoresis (AGE) constitutes a better medium through which MUC2 macromolecules can penetrate and hence be resolved. MUC2 molecules obtained from PC/AA (a benign colonic adenoma cell line) were extracted, and their molecular weights (varying between 15–32 × 106 Da) determined using Laser Light Scattering (LLS). These mucin molecules were reduced until 5–6 × 106 subunits were obtained. The reduced and unreduced mucin molecules were run on an AGE and Western blotting and visualized, but were too large for PAGE. For this reason, the mucin subunits were treated with trypsin to obtain 500–600 kDa fragments. These tryptic fragments were then run on PAGE and AGE, and their resolutions compared. We conclude that AGE is a more useful electrophoretic method for characterization of macromolecules like mucin glycoproteins than PAGE.Agarose gel electrophoresis of PC/AA cell layer extract (U: unreduced, intact form, R: reduced form).magnified imageAgarose gel electrophoresis of PC/AA cell layer extract (U: unreduced, intact form, R: reduced form).
Chiral Recognition Sites Converted from Tetrapeptide Derivatives Adopting Racemates as Print Molecules
Authors: Yoshikawa Masakazu , Izumi Jun‐ichiro 
Published: September 2003

AbstractMolecularly imprinted polymeric membranes were prepared from polystyrene resin bearing tetrapeptide derivatives H‐Asp(OcHex)‐Leu‐Asp(OcHex)‐Glu(OBzl)‐OCH2‐ (DLDE) consisting of D‐amino acid residues or L‐amino acid residues. The tetrapeptide derivatives were converted into chiral recognition sites by using not only an optically pure Boc‐Trp but also racemic Boc‐Trps as a print molecule. The chiral recognition ability depends on the combination of the absolute configuration of the print molecule and that of constituting amino acid residues. The membrane prepared from a DLDE derivative consisting of D‐amino acid residues and imprinted by Boc‐D‐Trp recognized the D‐isomer in preference to the corresponding L‐isomer and vice versa. In the present study, it was also made clear that racemic print molecules were effective in generating chiral recognition sites. The affinity constant of the generated chiral recognition site was determined to be 9.6 × 103 mol−1 · dm3, which was independent of the molecular imprinting conditions. Enantioselective permeation was attained by applying electrodialysis. An optimum permselectivity of 5.9, which corresponds to the adsorption selectivity, was attained.Summary of the molecularly imprinted polymeric membranes studied.magnified imageSummary of the molecularly imprinted polymeric membranes studied.
Physical Hydrogels of Poly(vinyl alcohol) with Different Syndiotacticity Prepared in the Presence of Lactosilated Chitosan Derivatives
Authors: Masci Giancarlo , Husu Ivan , Murtas Susanna , Piozzi Antonella , Crescenzi Vittorio 
Published: September 2003

AbstractPoly(vinyl alcohol) (PVA) physical hydrogels were prepared by repeated freeze–thawing cycles using aqueous solutions of two PVA samples having different degrees of syndiotacticity, a‐PVA and s‐PVA with 55% and 61% of syndiotactic diads, respectively. The hydrogels were prepared in the presence of different amounts of lactosilated chitosan derivatives (LC) of different molecular weight. The PVA stereoregularity was found to have a dramatic effect on the amount of PVA incorporated into the hydrogels, leading to remarkable differences in the swelling degree and porosity of a‐PVA and s‐PVA hydrogels. A significant amount of LC was retained in the hydrogels after equilibrium swelling. The swelling of the a‐PVA hydrogels was found to increase significantly by increasing the amount of LC while it was only slightly increased in the case of s‐PVA hydrogels. The amount of LC released after equilibrium swelling was lower when chitosan derivatives with higher molecular weights were used. Increased initial concentrations of LC resulted in much higher porosity of the hydrogels. TGA and DSC studies showed that LC is stabilized by the incorporation in the PVA hydrogels. The melting temperature of the crystalline regions of PVA was not significantly influenced by LC. Conversely, the extension of the crystalline domains increased in the presence of LC. The retention of a chitosan derivative bearing β‐D‐galactose side chain residues makes these hydrogels potentially useful as scaffolds for hepatocytes culture.Scanning electron micrographs of PVA‐LC hydrogels: (a) a‐PVA; (b) a‐PVA/LC150 80:20; (c) a‐PVA/LC150 50:50.magnified imageScanning electron micrographs of PVA‐LC hydrogels: (a) a‐PVA; (b) a‐PVA/LC150 80:20; (c) a‐PVA/LC150 50:50.