bluuebunny/crossref_metadata_2025 huggingface dataset:
Mass spectrometric investigation of gallium and zirconium complexes with octaethylporphyrin and tetraphenylporphyrin
Authors: Witowska‐Jarosz Janina , Górski Łukasz , Malinowska Elźbieta , Jarosz Maciej
Published: December 2002

Gallium and zirconium octaethylporphyrin (OEP) and tetraphenylporphyrin (TPP) were examined by electrospray ionization (ESI) mass spectrometry. All systems were prepared in dichloromethane with addition of a stabilizing lipophilic anionic agent, sodium tetrakis[3,5‐bis(trifluoromethyl)phenyl]borate (NaTFPB). In the solutions examined both monomeric and dimeric metalloporphyrins were observed. In the gallium‐OEP mass spectrum the ion registered at m/z 601 was attributed to monomeric [Ga(OEP)]+ and that at m/z 1219 to the dimeric form, [{Ga(OEP)}2OH]+. Peaks appearing in the ESI mass spectra of zirconium systems were substantially less intense, probably owing to the relatively low stability of complexes of this metal caused by its different geometry preferences. The most abundant monomeric zirconium‐OEP complexes were [{Zr(OEP)OH}]+ (m/z 639) and [Zr(OEP)Cl]+ (m/z 657), and dimeric [{Zr(OEP)OH}2]2+ (m/z 639). Analogous species were observed in the Zr(TPP) system: monomeric [{Zr(OEP)OH}]+ (m/z 719) and [Zr(TPP)Cl]+ (m/z 737) and dimeric [{Zr(TPP)OH}2]2+ (m/z 719). In both cases series of other dimers, e.g. [{Zr(OEP)}2O2H]+ (m/z 1277), [{Zr(OEP)OH}2Cl]+ (m/z 1313), [Zr(TPP)2O2H]+, (m/z 1437), [{Zr(TPP)OH}2OH]+ (m/z 1455) and [{Zr(TPP)OH}2Cl]+ (m/z 1473), appeared. The results obtained confirmed the hypothesis concerning the formation of dimeric metalloporphyrins in solutions containing stabilizing lipophilic anions. It also allowed us to explain the super‐Nernstian slopes of the calibration curves towards primary anions of ion‐selective electrodes with membranes containing the examined metalloporphyrins. Copyright © 2002 John Wiley & Sons, Ltd.
Analyses of gas composition in vacuum systems by mass spectrometry
Authors: Řepa P. , Tesař J. , Gronych T. , Peksa L. , Wild J.
Published: December 2002

Analyses of the composition of residual gases for diagnostic purposes, analyses of the atmosphere enforced by the introduction of gases for technological purposes and analyses of gases released from analyte materials in numerous analytical methods (e.g. TSD, SIMS) are frequently carried out in vacuum systems. There is only a small amount of gas available, in the vacuum system so the most important property of a mass spectrometer is high sensitivity. As a consequence, the mass resolution is usually low. Moreover, a low outgassing rate of the mass spectrometer itself and all parts connecting it to the vacuum system is required. Dynamic mass spectrometry satisfies these demands best. Quadrupole mass spectrometers are almost solely utilized in applications, although the time‐of‐flight mass spectrometer has come into use recently. The main disadvantage of the quadrupole mass spectrometer is a strong dependence of the sensitivity and the mass discrimination factor on the stability of the supply voltages. Together with the necessity to use multipliers for detection of the ion current, this leads to a requirement for frequent recalibration. Another serious problem, that is met in such applications is the estimation of the gas composition from the measured mass spectra. Usually, the analyte gas mixtures consist of various individual gases, or at least are measured on a background of such mixtures. This implies a requirement for the exact knowledge of the fragmentation pattern of the gases, and again the necessity for frequent calibration over a satisfactorily wide range of mass numbers. Some theoretical considerations and some experimental results obtained by the authors are presented. Copyright © 2002 John Wiley & Sons, Ltd.
Atmospheric pressure ionization mass spectrometry of purine and pyrimidine markers of inherited metabolic disorders
Authors: Fryčák Petr , Hušková Renata , Adam Tomáš , Lemr Karel
Published: December 2002

Purines and pyrimidines are of interest owing to their significance in processes in living organisms. Mass spectrometry is a promising analytical tool utilized in their analysis. Two atmospheric pressure ionization (API) methods (electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI)) in both negative and positive modes applied to selected purine and pyrimidine metabolites (markers of inherited metabolic disorders) were studied. APCI is less sensitive to alkali metal cations present in a sample and offers higher response than ESI for studied compounds. Both of the techniques afford quasi‐molecular ions, but fragmentation also occurs to a certain extent. However, the application of collision‐induced dissociation of quasi‐molecular ions is essential to confirm a certain metabolite in a sample. Fragmentation of both positive and negative ions was evaluated using multi‐stage mass spectrometric experiments. Typical neutral losses correspond to molecules NH3, H2O, HCN, CO, H2NCN, HNCO and CO2. The ion [NCO]− arises in the negative mode. The cleavage of the glycosidic C—N bond is characteristic for relevant metabolites. Other neutral losses (CH2O, C2H4O2 and C3H6O3) originate from fragmentation of the glycosidic part of the molecules. In addition to fragmentation, the formation of adducts of some ions with applied solvents (H2O, CH3OH) was observed. The composition of the solution infused into the ion source affects the appearance of the mass spectra. Tandem mass spectra allow one to distinguish compounds with the same molecular mass (uridine–pseudouridine and adenosine–2'‐deoxyguanosine). Flow injection analysis APCI‐MS/MS was tested on model samples of human urines corresponding to adenosine deaminase deficiency and xanthine oxidase deficiency. In both cases, the results showed potential diagnostic usefulness. Copyright © 2002 John Wiley & Sons, Ltd.
Development of a gas chromatographic/ion trap mass spectrometric method for the determination of levoglucosan and saccharidic compounds in atmospheric aerosols. Application to urban aerosols
Authors: Pashynska Vlada , Vermeylen Reinhilde , Vas Gyorgy , Maenhaut Willy , Claeys Magda
Published: December 2002

We developed and validated a gas chromatographic/ion trap mass spectrometric method for the determination of levoglucosan and the related monosaccharide anhydrides, mannosan, galactosan and 1,6‐anhydro‐β‐D‐glucofuranose in urban atmospheric aerosols collected on quartz fiber filters. The method is based on extraction with dichloromethane–methanol (80 : 20, v/v), trimethylsilylation, multiple reaction monitoring in the tandem mass spectrometric mode using the ion at m/z 217, and the use of an internal standard calibration procedure with the structurally related compound methyl β‐L‐arabinopyranoside. In addition, the method allows the quantification of other saccharidic compounds, arabitol, mannitol, glucose, fructose, inositol and sucrose, which were found to be important in summer aerosols. The recovery of levoglucosan was estimated by spiking blank filters and was better than 90%. The precision evaluated by analyzing parts of the same filters was about 2% for the monosaccharide anhydrides and 7% for the other saccharidic compounds in the case of a winter aerosol sample, and the corresponding values for a summer aerosol sample were 5% and 8%. The method was applied to urban PM10 (particulate matter of <10 µm aerodynamic diameter) aerosols collected at Ghent, Belgium, during a 2000–2001 winter and a 2001 summer episode and revealed interesting seasonal variations. While monosaccharide anhydrides were relatively more important during the winter season owing to wood burning, the other saccharidic compounds were more prevalent during the summer season, with some of them, if not all, originating from the vegetation. Copyright © 2002 John Wiley & Sons, Ltd.
An unusual rearrangement of Zofenopril, a new ACE inhibitor drug: mass spectrometric and conformational studies
Authors: Cartoni Antonella , Altamura Maria , Animati Fabio , Balacco Giuseppe , Cosi Riccardo , Ettorre Alessandro , Madami Andrea , Triolo Antonio
Published: December 2002

Zofenopril (1) is a new ACE inhibitor, used in therapy for hypertension and post‐myocardial infarction. The protonated quasi‐molecular ion (m/z 430) of 1, obtained under positive electrospray ionization conditions, loses a benzoic acid molecule (m/z 308), which in turn decomposes via loss of CO (m/z 280) when low‐energy collisional‐induced dissociation (CID) and in‐source experiments are performed. This rearrangement is the main fragmentation process and can be observed both in‐source and in the product ion tandem mass spectra, using either an ion trap or a triple quadrupole instrument.

Other known diastereoisomers of 1, an impurity with an acetyl in the place of the benzoyl group (2) and an impurity with two propanoyl chains in series (3), give the same rearrangement. On the other hand, the mass spectra of the methyl ester (4) and an impurity with two proline moieties (5) do not show this unusual fragmentation. Time‐resolved CID spectra of 1 show that the rearrangement occurs after about 2 ms, a time scale comparable to those of the other non‐rearrangement cleavages. These experiments suggest a conformation in the gas phase for 1 in which the benzoyl group is close to the hydroxyl of the carboxylic acid group, from which the rearrangement could readily occur. Since compounds 4 and 5 do not show the same behaviour, the presence of a carboxylic acid in the proline ring seems to play a crucial role in the rearrangement, probably due to an intramolecular hydrogen bond. To confirm this hypothesis, deuterium exchanges in mass spectrometric experiments and a conformational analysis via computational methods were performed. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of 17β‐estradiol in bovine plasma: development of a highly sensitive technique by ion trap gas chromatography–tandem mass spectrometry using negative chemical ionization
Authors: Biancotto Giancarlo , Angeletti Roberto , Traldi Pietro , Silvestri Massimiliano , Saccon Mauro , Guidugli Federico
Published: December 2002

A novel approach to the determination of 17β‐estradiol in bovine plasma is presented. The observed enhanced sensitivity is gained by the application of tandem mass spectrometry (MS) fragmentation to a stable, well characterized negative ion produced by chemical ionization (methane as reagent gas). A specific derivatizing reactant is employed (pentafluorobenzyl bromide), combined with bis‐trimethylsilyltrifluoroacetamide, to favor the formation of a diagnostic precursor negative ion. Plasma samples are purified through a C18 solid phase extraction column and derivatized before gas chromatography–MS analysis. The accuracy and the precision of the method, tested over a set of spiked samples, were satisfactory. The limit of detection was found to be 5 pg ml−1 and the limit of quantification was fixed at 20 pg ml−1. The fragmentation pattern is fully explained and the method is applicable for the official analysis of bovine plasma for the detection of 17β‐estradiol according to the European criteria 256/93 and to the draft SANCO/1805/2000 rev. 3. The quantification of incurred positive samples was performed according to the proposed procedure and compared with the results obtained by standardized radio immuno assay; the estimated concentrations were significantly similar. Copyright © 2002 John Wiley & Sons, Ltd.
Direct stereochemical assignment of hexose and pentose residues in flavonoid O‐glycosides by fast atom bombardment and electrospray ionization mass spectrometry
Authors: Cuyckens Filip , Shahat Abdelaaty A. , Pieters Luc , Claeys Magda
Published: December 2002

Mass spectrometric methods have been developed which allow the direct stereochemical assignment of terminal monosaccharide residues in flavonoid O‐glycosides without the need for chemical hydrolysis. Standards containing a glucose, galactose, mannose, xylose, arabinose or apiose residue were examined because these monosaccharides are by far the most commonly encountered in flavonoid glycosides. Following acetylation, the major peracetylated sugar related fragments, generated by fast atom bombardment (FAB) or electrospray ionization (ESI), were selected for collisional activation employing a broad range of collision energies. Both FAB and ESI proved to be useful as ionization techniques. Stereoselective fragmentation was achieved and allowed us clearly to differentiate and characterize isomeric monosaccharide residues. The method developed was successfully applied to an unknown flavonoid containing a terminal pentose and hexose residue which was isolated from Farsetia aegyptia. Copyright © 2002 John Wiley & Sons, Ltd.
Isomerization and dissociation of C2X5+ and C2X4+· ions (X = Cl, F) from chlorofluoroethanes in an ion trap mass spectrometer
Authors: Marotta Ester , Paradisi Cristina
Published: December 2002

The collision‐induced dissociation of C2X5+ (C2Cl2F3+, C2Cl3F2+ and C2Cl4F+) and C2X4+· ions (C2ClF3+·, C2Cl2F2+·, and C2ClF3+·) derived from three chlorofluoroethanes (the isomeric 1,1,1‐ and 1,1,2‐trichlorotrifluoroethane and 1,1,1,2‐tetrachlorodifluoroethane) was investigated by means of multi‐stage mass spectrometric (MSn) experiments in an ion trap mass spectrometer. The observation of a common dissociation pattern for ions of any given elemental composition suggests that the experiments could not differentiate isomeric C2X5+ ions formed from different neutral precursors and originally having different structures. For any given elemental composition, a common dissociation pattern was observed, suggesting that energy barriers for isomer interconversion are lower than for dissociation. For ions containing two or more fluorine atoms, the major (in some cases unique) dissociation involves C—C cleavage to form CX3+ and CF2. Energetically, CF2 loss is always the most favorable reaction; mechanistically it implies, at least in some cases, rearrangement via halogen transfer from one carbon to the other (for example, in the case of the C2Cl2F3+ species derived from 1,1,1‐trichlorotrifluoroethane, which should have initially the Cl2C+—CF3 structure). Similar behavior was observed with C2X4+· ions produced both from the three chlorofluoroethanes and from model alkenes (trifluorochloroethene and tetrachloroethene). The dissociation behavior of these C2X4+· species is characteristic of the ion composition, with no memory of the original neutral precursor structure. Specifically, C2Cl2F2+· ions dissociate uniquely via loss of CF2, C2ClF3+· ions eliminate preferentially CF, with CF2 loss being only a minor reaction, whereas C2Cl3F+· and C2Cl4+· dissociate exclusively via Cl elimination. Copyright © 2002 John Wiley & Sons, Ltd.
Gene expression profiling using advanced mass spectrometric approaches
Authors: Paša‐Tolić Ljiljana , Lipton Mary S. , Masselon Christophe D. , Anderson Gordon A. , Shen Yufeng , Tolić Nikola , Smith Richard D.
Published: December 2002

In the era of systems biology, computational and high‐throughput experimental biological approaches are increasingly being combined to provide global snapshots of entire genomes and proteomes under tissue‐ and disease‐specific conditions. The aim is to identify proteins changing in concentration and/or post‐translational state and/or location, and develop a better molecular level understanding of the operation of biological systems. Here we describe an approach for comparative proteomics that builds upon the combination of high‐performance nano‐scale separations with the high‐mass measurement accuracy, mass‐resolving power and sensitivity of Fourier transform ion cyclotron resonance mass spectrometry to provide broad dynamic range, comprehensive and quantitative proteome measurements. Copyright © 2002 John Wiley & Sons, Ltd.
Nitrification activity in tropical rain forest soils of the Coastal Lowlands and Atherton Tablelands, Queensland, Australia
Authors: Kiese Ralf , Papen Hans , Zumbusch Elisabeth , Butterbach‐Bahl Klaus
Published: December 2002

Intact soil cores from a montane tropical rain forest site in the Atherton Tablelands (Kauri Creek) and from a lowland tropical rain forest site in the Coastal Lowlands (Bellenden Ker), Queensland, Australia were investigated during different hygric seasons for the magnitude of gross nitrification rates using the Barometric Process Separation technique (BaPS). Pronounced seasonal variations of gross nitrification rates were found at both sites with highest values during the transition period between dry and wet season (montane site: 24.0 mg N (kg SDW)—1 d—1; lowland site: 13.1 mg N (kg SDW)—1 d—1) and significantly lower rates of gross nitrification during the dry and wet season. Rates of gross nitrification were always higher at the montane site than at the lowland site, but the opposite was found for N2O emissions. The results indicated that the high losses of N2O at the lowland tropical rain forest site may be contributed largely by high denitrification activity due to its wetter and warmer climate as compared to the dryer and colder climate at the montane tropical rain forest site. This conclusion was supported by analysis of cell numbers of microbes involved in N‐cycling. Higher numbers of denitrifiers were present at the lowland site, whereas higher numbers of nitrifiers were found at the montane site.
Polycyclic aromatic hydrocarbons (PAHs) in peat and plants from selected peat‐bogs in the north‐east of Poland
Authors: Malawska Małgorzata , Bojakowska Izabela , Wiłkomirski Bogusław
Published: December 2002

The concentrations of polycyclic aromatic hydrocarbons (PAHs) were analyzed in samples of peat and of two plant species (Pinus sylvestris and Ledum palustre) overgrowing peat‐bogs in the north‐east of Poland. Peat samples were collected from different depths according to the stratigraphic profile of the peat bogs. The total concentrations of the 16 anthropogenic PAHs (15 from the US EPA list and benzo[e]pyrene) in all peat samples were between 70 and 439 ng g—1. The concentration for the same compounds in pine needles (Pinus sylvestris) and Dutch Myrthe leaves (Ledum palustre) varied between 194 and 1039 ng g—1. A noticeably high fluorene concentration in Dutch Myrthe leaves was found at some sites. In all peat samples 3‐ring compounds were predominant (55 to 319 ng g—1). There were less 4‐ring PAHs (15 to 110 ng g—1) and the least common PAHs were 5‐ring and 6‐ring compounds (0 to 81 ng g—1 for both groups). In some peat samples, the perylene concentration largely exceeds of the total concentration of all the other PAHs investigated. The high content of perylene in bottom layers could result from the processes of perylene sorption from water during peat‐bog formation or from biogenic formation of perylene.
Some investigations into the behavior of pentabromodiphenyl ether (PeBDE) in soils
Authors: Litz Norbert
Published: December 2002

Pentabromodiphenyl ethers (PeBDEs) are components of brominated flame retardants which have been detected in various environmental media (waste water, sewage sludge, sediments, and aquatic biota). They are ”︁priority pollutants”. Sewage sludge from 20 different sewage treatment plants under summer and winter conditions showed PeBDE levels in primary sludge of up to 70 μg kg—1 with a dominant range of 5—20 μg kg—1. To insure a safe sludge use in agriculture, sorption, mobility, and dissipation experiments using soil substrates were conducted. PeBDE was bound strongly to organic matter (Koc = 125,000) while Kd values after FREUNDLICH of about 90 and 700 were obtained for clay and sand, respectively, and of 45,000 for humus. Less than 0.001 % was found in eluates from laboratory lysimeters, and about 91 % remained at a depth of 0—3 cm. Thus PeBDE has a low mobility. In the indicative dissipation tests, the recovery rate after 3 weeks was about 50 %, and about 20—25 % was still detectable after 8 weeks. PeBDE proved to be less persistent than previously assumed. A formation of bound residues is presumed to be likely. Only a small difference was found between aerobic and anaerobic dissipation. The strong fixation in soil suggests a need to clarify whether PeBDE accumulates in soil.
Distribution of Cd in the vicinity of a metal smelter: Interpolation of soil Cd concentrations with regard to regulative limits
Authors: Altfelder Sven , Beyer Christof , Duijnisveld Wilhelmus H. M. , Schneider Jürgen , Streck Thilo
Published: December 2002

The German soil protection regulation (BBodSchV) requires the investigation and evaluation of sites with known, or suspected contamination. The purpose of this study is the application of geostatistical methods to locate hazardous zones within such a site and to estimate the amount and uncertainty of the contaminant load in these zones. The study site is an area around a metal smelter in the city of Nordenham, Germany, where among other heavy metals, Cd was released to the environment by dust emissions for many decades. In an earlier study soil cores were taken in the area and analyzed for Cd using various extraction methods. After translation of data to results corresponding to a single extraction method using linear regression analysis, Cd concentrations were mapped by ordinary and lognormal kriging. Crossvalidation showed that both methods perform similarly. However, neither ordinary nor lognormal kriging were able to account for the uncertainty of the kriged estimates. We repeated ordinary kriging with a relative variogram having a unit sill. The estimated relative kriging variance was scaled locally. This method considerably improved the estimation of uncertainty. Subsequently, we estimated Cd contents for the land use dependent size of support as specified in the BBodSchV. The kriged Cd estimates as well as their uncertainty were evaluated with regard to limits set by the BBodSchV. Parts of the area which may be declared safe based on merely the kriged estimates, can actually exceed a sanction or test limit by a chance of up to 50 % when uncertainty is also considered. Within the BBodSchV a recommended limit should therefore always be accompanied by a tolerable uncertainty that it may be exceeded on a given support (e.g. 5 %).
Nodulation and N2 fixation of faba bean (Vicia faba L.) after soil amendment with crop residues
Authors: Kadiata Bakach Dikand , Yan Feng , Schubert Sven
Published: December 2002

The effect of prior soil amendment with different N sources at 50 mg N (kg soil)—1 on nodulation and N2 fixation of faba bean (Vicia faba L. cv. Troy) using wheat (Triticum aestivum L. cv. Star) as reference crop was assessed in a pot experiment. Four treatments viz legume manure (LEGM) as clover shoots, cereal manure (CEREM) as barley straw, N fertilizer (FERT‐N) as Ca(NO3)2, and no‐manure control (NOMAN) were investigated consecutively at 45, 70, and 90 days after sowing (DAS). Faba bean nodulated profusely, with an increase on average from 629 nodules per pot at 45 DAS to nearly 2.3‐ and 3.3‐fold at 70 and 90 DAS, respectively. Low nodule numbers and nodule dry matter occurred under FERT‐N and CEREM, whereas high values were found for NOMAN and LEGM. Soil amendment affected percent N2 fixation in relation to N source and plant age. Highest percent N2 fixation (≥ 90 %) was found under the lowest N‐supplying amendments, no‐manure, and cereal manure, respectively. FERT‐N depressed N2 fixation particularly at 45 DAS when N2 fixation was reduced to as low as 23 %. The rise in N2 fixation thereafter suggests that faba bean adjusted after depletion of mineral N in the soil. N2 fixation was also decreased after cereal straw application, even though N concentration in faba bean plants was high. The results indicate that plant residues, both with high and low N concentration, applied to soil to raise its fertility may interfere with N2 fixation of faba bean.
Stage of development affects penetration of calcium chloride into apple fruits
Authors: Schlegel Thomas K. , Schönherr Jörg
Published: December 2002

Using young fruits or fruit segments, rates of penetration of 45CaCl2 across apple fruit cuticles (Malus x domestica) were studied during fruit development in two consecutive years (’︁Golden Delicious’ in 2000, ’︁Cox Orange Pippin’ and ’︁Boskoop’ in 2001). The aqueous donor solutions contained 5 g l—1 CaCl2 and 0.2 g l—1 Glucopon 215 CSUP as wetter. A droplet (5 μl) was applied to each fruit disc and allowed to dry within 1 h. Amounts penetrated were estimated immediately after droplet drying (0 h) and after 6 and 24 h penetration, respectively. Temperature during penetration was 20 �C and 100 % humidity was maintained throughout the experiment, once the droplet had dried. Rates of penetration were greatly affected by the stage of fruit development. With all varieties tested, highest rates were measured during the early stages of fruit development (before June drop) when approx. 100 % of the CaCl2 applied penetrated within 24 h. After June drop, when trichomes had vanished and most stomata developed into lenticels, penetration rates decreased rapidly and large variability among the samples developed. This pattern was similar with all three varieties. The involvement of trichomes, stomata, and lenticels as preferential sites of penetration of calcium chloride across the apple fruit cuticles is discussed. Using a model calculation, it is argued that ten or more spray applications are needed to significantly increase calcium contents of apples. This has two causes: Only a small fraction of the spray liquid is intercepted by the fruits, and penetration can be rather slow.
Detectability enhancement of spectrophotometric detectors by the use of multidimensional gas chromatography
Authors: Medina Juan Carlos , Griffith James , Houston K. Ray , Winniford Bill
Published: December 2002

Multidimensional gas chromatography (2D GC) is demonstrated as a way to improve limits of detectability of spectrophotometric detectors. UV and IR detectors are generally less sensitive than mass spectrometers or other GC detectors. This has placed some limitations on the useful capabilities provided by spectrophotometric detectors, such as the ability to provide structure‐related information for a particular analyte. In this paper, we report results from interfacing a 2D GC instrument to a UV detector. Symmetry factor and the ratio of retention time divided by peak width did not show deterioration of the quality of chromatography when a megabore column was used with this detector. Furthermore, an increase in the limits of detectability over that attainable in a single‐column system was realized by using the 2D GC system. However, the low flow (1 mL/min) imposed by the use of a microbore column (250 μm ID) caused significant tailing when the UV detector was used.
Factors influencing chromatographic data in fast gas chromatography with on‐column injection
Authors: Matisová Eva , Šimeková Mária , Hrouzková Svetlana , Korytár Peter , Dömötörová Milena
Published: December 2002

The use of larger volume injection with on‐column injection and fast GC commercial instrumentation was evaluated with the model mixture of n‐alkanes of a broad range of volatility (C10–C28). The presented configuration allows introduction of 40–80‐fold larger sample volumes without any distortion of peak shapes compared to “usual” fast GC set‐ups using narrow‐bore columns. A normal‐bore retention gap (1–5 m×0.32 mm ID) was coupled to a narrow‐bore (5 m×0.1 mm ID×0.4 μm film thickness) analytical column using a standard press‐fit connector. The connection was tight and reliable, and hence suitable for hydrogen as carrier gas. The effect of pre‐column and analytical column connector, injection volume, pre‐column length, column inlet pressure, and analyte volatility on peak shape, peak broadening, and focusing are discussed. The precision of chromatographic data measurements and peak capacity under optimised temperature programmed conditions for fast separations with large volume injection were found to be very good. The presented fast GC set‐up with on‐column injection extends the applicability of the technique to trace analysis.
Polymer electrostatics: detection and speciation of trapped electric charges by electric probe and analytical electron microscopy
Authors: Galembeck Fernando , Alberto Carlos , Leite Paula , do Carmo Maria , da Silva V.M. , Keslarek Amauri José , Alberto Carlos , Costa Rodrigues , Teixeira‐Neto Érico , Rippel Márcia Maria , Braga Melissa
Published: December 2002

This work reviews new probe and electron microscopy approaches for the detection of charged domains in insulating polymers, as well as for the identification of the charge‐bearing species: scanning electric potential microscopy (SEPM), electric force microscopy (EFM) and energy‐loss spectroscopy imaging in the transmission electron microscope (ESI‐TEM). The SEPM and EFM micrographs show patterned domains bearing excess electric charges and extending for tens of nanometers, in polymer latex particles and films. The charged species are identified by ESI‐TEM as emulsion polymerization initiator and surfactant residues, as well as the associated counter‐ions. Charged domains are also observed in common thermoplastic polymers, producing unexpectedly large electric potential gradients.
Hybrid organic‐inorganic polymer networks based on the copolymerization of methacryloxypropyl‐silsesquioxanes and styrene
Authors: Eisenberg Patricia , Lucas Juan C. , Williams Roberta J.J.
Published: December 2002

Silsesquioxanes synthesized by the condensation of (3‐methacryloxypropyl)trimethoxysilane with concentrated formic acid, were copolymerized with styrene using benzoyl peroxide as initiator. When the ratio of styrene (S) to methacrylic (M) unsaturations was S/M > 1, the reaction attained an almost complete conversion as shown by the total reaction heat determined by differential scanning calorimetry. Several properties of the resulting hybrid organic‐inorganic polymer networks were determined as a function of the silsesquioxane amount used in the formulation. Increasing the silsesquioxane fraction led to an increase of the glass transition temperature up to a point where devitrification was not observed prior to decomposition, an increase of the elastic modulus in the rubbery state, a decrease of the intensity of tan δ, and an increase of both Barcol hardness and thermal stability.
Compatibilization of elastomer‐based blends
Authors: Scares Bluma G. , Sirqueira Alex S. , Oliveira Marcia G. , Almeida Mauricio S.M.
Published: December 2002

The reactive compatibilization of ethylene‐propylene‐diene (EPDM)‐based dissimilar elastomer blends has been investigated in terms of mechanical properties and swelling degree. The use of mercapto‐functionalized copolymers resulted in an improvement of mechanical properties of natural rubber‐EPDM blends. The mercapto‐groups are able to react with the carbon‐carbon double bonds of the high diene rubber, resulting in a good interaction between phases. These interactions were confirmed by the amount of insoluble material obtained in non‐vulcanized blends. From dynamic mechanical properties and swelling degree, one can suggest a covulcanization process in these blends cured with sulfur‐based system.

Blends composed by nitrile rubber with EPDM displayed good results in terms of mechanical properties when mercapto‐functionalized EVA was employed instead of functionalized EPDM, probably because of the higher polarity of the former associated to its lower viscosity. Additionally, an improvement on mechanical properties was also achieved by using EPDM functionalized with mercapto or anhydride groups in combination with nitrile rubber functionalized with epoxy or oxazoline groups.
Modulation of JB6 mouse epidermal cell transformation response by the prostaglandin F2α receptor
Authors: Weber Thomas J. , Markillie Lye M. , Chrisler William B. , Vielhauer George A. , Regan John W.
Published: December 2002

Prostaglandin F2α (PGF2α) modulates clonal selection processes in the mouse skin model of carcinogenesis. In this study we investigated whether JB6 mouse epidermal cells expressed a functional PGF2α receptor (FP) coupled with a cell‐transformation response. Treatment of JB6 cells with an FP agonist (fluprostenol) potently (pM‐nM) increased anchorage‐dependent and anchorage‐independent growth. Inositol phospholipid accumulation and extracellular signal–regulated kinase (Erk) activity were increased in cells treated with FP agonists, consistent with established FP‐related signal transduction. FP mRNA was detected by reverse transcription–polymerase chain reaction, and the average specific [3H]PGF2α binding was 8.25 ± 0.95 fmol/mg protein. Erk activity and colony size were increased by cotreatment of JB6 cells with epidermal growth factor (EGF) and fluprostenol to a greater extent than with either treatment alone, whereas the cotreatment effect on colony number appeared to be simply additive. Collectively, our data indicated that JB6 cells expressed a functional FP coupled with transformation‐related signal transduction and the regulation of clonal selection processes. Erk activity appears to be a convergence point in the EGF and FP pathways. The data raise the possibility that the FP contributes to clonal selection processes but probably plays a more important role as a response modifier. © 2002 Wiley‐Liss, Inc.
Expression, localization, and activity of glycogen synthase kinase 3β during mouse skin tumorigenesis
Authors: Leis Hugo , Segrelles Carmen , Ruiz Sergio , Santos Mirentxu , Paramio Jesús M.
Published: December 2002

Glycogen synthase kinase 3 (GSK‐3) is a protein kinase that plays essential roles in the control of several developmental, metabolic, and apoptotic processes. Owing to its negative actions on several oncogenic insults, it has been considered a putative functional tumor suppressor. We studied the expression, activity, and localization of GSK‐3β during the process of chemically induced two‐stage mouse skin carcinogenesis and also in the tumors generated upon subcutaneous injection of Akt‐transformed keratinocytes. We found that GSK‐3 activity was downregulated at the later stages of promotion by tyrosine 216 dephosphorylation and serine 9 phosphorylation. The data obtained with Akt‐transformed keratinocytes clearly suggested the involvement of Akt in serine 9 phosphorylation of GSK‐3β. Finally, besides functional inactivation, significant basal activity of GSK‐3β was detected in all cases, indicating that this enzyme provides essential functions to malignant keratinocytes. © 2002 Wiley‐Liss, Inc.
Downregulation of expression of a novel cadherin molecule, T‐cadherin, in basal cell carcinoma of the skin
Authors: Takeuchi Tamotsu , Liang Sheng‐Ben , Ohtsuki Yuji
Published: December 2002

T‐cadherin appears to act as a tumor‐suppressor factor in various cancers. Downregulation of T‐cadherin is caused by a combination of allelic loss and hypermethylation of the T‐cadherin promoter region and is related to cancer invasion. To elucidate the molecular mechanism of invasiveness of basal cell carcinoma of the skin, T‐cadherin expression was investigated in archival pathological tissue sections made up of normal counterparts of skin and various types of basal cell carcinoma. Immunohistochemical staining showed that T‐cadherin was not expressed in 38 of 51 (75%) basal cell carcinoma specimens, whereas normal counterparts of the skin appeared to express abundant T‐cadherin. Loss of heterozygosity in intron 1 of the T‐cadherin gene was found in four of 20 informative cases that did not express T‐cadherin. Aberrant methylation of the T‐cadherin promoter region also was found in six of 25 basal cell carcinomas by methylation‐specific polymerase chain reaction. In contrast, no structural alternations were found in two loss of heterozygosity–positive basal cell carcinomas on sequence analysis. These findings indicated that T‐cadherin expression was downregulated by a combination of allelic loss and aberrant methylation in basal cell carcinoma of the skin. Loss of T‐cadherin expression might be related to the biological behavior of basal cell carcinoma. In addition, results of the present study suggested that downregulation of T‐cadherin in various cancers might be related to tumor invasiveness rather than metastasis, because basal cell carcinoma of the skin principally lacks metastatic activity. © 2002 Wiley‐Liss, Inc.
Generation of free radicals and induction of DNA adducts by activation of heterocyclic aromatic amines via different metabolic pathways in vitro
Authors: Moonen Harald J. J. , Briedé Jacob J. , van Maanen Jan M. S. , Kleinjans Jos C. S. , de Kok Theo M. C. M.
Published: December 2002

Food‐derived heterocyclic aromatic amines (HCAs) have proved to be carcinogenic in both rodents and nonhuman primates. Two different metabolic pathways are suggested for the metabolic activation of HCA. The hepatic pathway proceeds via a two‐step process involving N‐hydroxylation by cytochrome P4501A2 and subsequent O‐acetylation by N‐acetyltransferase‐2. An alternative pathway may be of particular interest in extrahepatic tissues and proceeds via one‐electron oxidation catalyzed by prostaglandin H synthase (PHS), rendering free‐radical metabolites. In this study, we investigated the metabolic activation of two HCAs, 2‐amino‐3‐methylimidazo[4,5‐f]quinoline (IQ) and 2‐amino‐1‐methyl‐6‐phenylimidazo[4,5‐b]pyridine (PhIP), by two different enzyme systems in vitro, generating different primary and secondary reactive metabolites. Rat liver S9 mix and PHS were used as the activating system and represent the hepatic and extrahepatic pathways, respectively. Electron‐spin resonance spectroscopy showed that both IQ and PhIP exerted inhibiting effects on PHS‐mediated formation of hydroxyl radicals during the conversion of arachidonic acid to prostaglandins. Evidence for the formation of HCA free radicals was presented in an indirect way by the formation of glutathione‐derived thiyl radicals, with purified PHS as the activating system. Activation by S9 mix did not result in the formation of detectable radical metabolites, showing that the two metabolic routes primarily led to the formation of different metabolites. In all electron‐spin resonance experiments, IQ appeared to be more effective than PhIP. In contrasts, DNA adduct analysis by means of 32P‐postlabeling showed similar adduct patterns for S9 and PHS in single‐stranded and double‐stranded salmon testes DNA after incubation with PhIP, indicating the ultimate formation of a common reactive intermediate. For IQ, activation by PHS led to an additional adduct spot that was not present after S9 activation. Furthermore, activation of IQ resulted in higher adduct levels compared with PhIP for both activation pathways. Overall, adduct levels were higher in single‐stranded DNA than double‐stranded DNA. Our results showed that the hepatic and extrahepatic pathways resulted in different primary metabolites, while the ultimate formation of a similar reactive intermediate for PhIP, possibly an arylnitrenium ion, suggested that both pathways could play an important role in the onset of carcinogenesis. © 2002 Wiley‐Liss, Inc.
Mechanism of action of a dominant negative c‐jun mutant in inhibiting activator protein‐1 activation
Authors: Thompson Eric J. , Gupta Ashok , Stratton M. Suzanne , Bowden G. Tim
Published: December 2002

The dominant negative c‐jun TAM‐67 has been shown to inhibit tumor promotion induced by 12‐O‐tetradecanoylphorbol‐13‐acetate and okadaic acid (OA). To better understand this phenomenon, we investigated the mechanism of action of TAM‐67 in response to OA. To identify the mechanism of action, we used a 6xHis‐tagged TAM‐67 as well as chimeric constructs of TAM‐67 that either cannot bind DNA or cannot heterodimerize with wild‐type transcription factors. The results of these studies indicated that TAM‐67 acts by blocking or squelching. The results of elecrophoretic mobility‐shift assays showed that TAM‐67 must act by squelching in response to OA, as TAM‐67 cannot be found in DNA‐binding complexes. We then identified some of the proteins with which TAM‐67 interacts. They include all members of the jun and fos families as well as the cAMP response element binding protein, activating transcription factor‐1, activating transcription factor‐2, and RelA (p65). Thus, we have shown that TAM‐67 squelches the induction of activating transcription factor‐1 transactivation in response to OA and that TAM‐67 is capable of interacting with proteins that control transactivation by binding to the 12‐O‐tetradecanoylphorbol‐13‐acetate response element, cAMP response element and nuclear factor‐κB sites. © 2002 Wiley‐Liss, Inc.
Gradual deregulation and loss of PCPH expression in the progression of human laryngeal neoplasia
Authors: Blánquez María José , Regadera Javier , Mariño Javier , Newman Robert E. , Notario Vicente
Published: December 2002

PCPH is a gene involved in the regulation of eukaryotic cell proliferation and stress response. Recently, analyses of human and animal solid tumors and cell lines suggested that PCPH protein deregulation may participate in neoplastic progression. To test this possibility, we first examined PCPH expression in several laryngeal carcinoma cell lines by Western analysis. The results showed the presence of altered PCPH polypeptides in these cells, accompanied by the loss of the PCPH form present in normal laryngeal epithelial cells, a deregulated expression pattern similar to that reported previously. We then analyzed PCPH expression in 59 dysplastic lesions of the human larynx, representative of the mild, moderate, and severe stages of the disease. Immunohistochemical data showed that, compared with normal laryngeal mucosa, PCPH expression in the dysplastic samples was associated with areas of epithelial cell maturation rather than with regions of increased proliferation. Furthermore, PCPH expression decreased parallel to the increase in cellular atypia of the dysplastic samples: PCPH either was expressed at very low levels or not expressed in cases of severe dysplasia/carcinoma in situ. This trend toward loss of PCPH expression along malignant progression of the larynx was confirmed by the low to null expression of PCPH in samples of invasive laryngeal carcinoma and by the complete absence of PCPH immunostaining in a laryngeal carcinoma–derived liver metastasis. These results indicated that PCPH protein analysis might allow for the distinction between grades of laryngeal dysplasia. In addition, detection of altered PCPH polypeptides by Western analysis potentially can be applied to the early identification of laryngeal squamous cell carcinoma. © 2002 Wiley‐Liss, Inc.
High b‐value q‐space analyzed diffusion‐weighted MRS and MRI in neuronal tissues – a technical review
Authors: Cohen Yoram , Assaf Yaniv
Published: December 2002

This review deals with high b‐value q‐space diffusion‐weighted MRI (DW‐MRI) of neuronal tissues. It is well documented that at sufficiently high b‐values (and high q‐values) neuronal water signal decay in diffusion experiments is not mono‐exponential. This implies the existence of more than one apparent diffusing component or evidence for restriction. The assignment of the different apparent diffusing components to real physical entities is not straightforward. However, the apparent slow diffusing component that was found to be restricted to a compartment of a few microns, if originating mainly from a specific pool and if assigned correctly, may potentially be used to obtain more specific MR images with regard to specific pathologies of the CNS. This review examines the utility of analyzing high b‐value diffusion MRS and MRI data using the q‐space approach introduced by Callaghan and by Cory and Garroway. This approach provides displacement probability maps that emphasize, at long diffusion times, the characteristics of the apparent slow diffusing component. Examples from excised spinal cord, where the experimental conditions for which the q‐space analysis of MR diffusion data was developed can be met or approached will be presented. Then examples from human MS patients, where q‐space requirement for the short gradient pulse is clearly violated, are presented. In the excised spinal cord studies, this approach was used to study spinal cord maturation and trauma, and was found to be more sensitive than other conventional methods in following spinal cord degeneration in an experimental model of vascular dementia (VaD). High b‐value q‐space DWI was also recently used to study healthy and MS diseased human brains. This approach was found to be very sensitive to the disease load in MS, compared with other conventional MRI methods, especially in the normal appearing white matter (NAWM) of MS brains. Finally, the potential diagnostic capacity embedded in high b‐value q‐space analyzed diffusion MR images is discussed. The potentials and caveats of this approach are outlined and experimental data are presented that show the effect of violating the short gradient pulse (SGP) approximation on the extracted parameters from the q‐space analysis. Copyright © 2002 John Wiley & Sons, Ltd.
Diffusion tensor fiber tracking of human brain connectivity: aquisition methods, reliability analysis and biological results
Authors: Lori N. F. , Akbudak E. , Shimony J. S. , Cull T. S. , Snyder A. Z. , Guillory R. K. , Conturo T. E.
Published: December 2002

We present a description, biological results and a reliability analysis for the method of diffusion tensor tracking (DTT) of white matter fiber pathways. In DTT, diffusion‐tensor MRI (DT‐MRI) data are collected and processed to visualize the line trajectories of fiber bundles within white matter (WM) pathways of living humans. A detailed description of the data acquisition is given. Technical aspects and experimental results are illustrated for the geniculo‐calcarine tract with broad projections to visual cortex, occipital and parietal U‐fibers, and the temporo‐calcarine ventral pathway. To better understand sources of error and to optimize the method, accuracy and precision were analyzed by computer simulations. In the simulations, noisy DT‐MRI data were computed that would be obtained for a WM pathway having a helical trajectory passing through gray matter. The error vector between the real and ideal track was computed, and random errors accumulated with the square root of track length consistent with a random‐walk process. Random error was most dependent on signal‐to‐noise ratio, followed by number of averages, pathway anisotropy and voxel size, in decreasing order. Systematic error only occurred for a few conditions, and was most dependent on the stepping algorithm, anisotropy of the surrounding tissue, and non‐equal voxel dimensions. Both random and systematic errors were typically below the voxel dimension. Other effects such as track rebound and track recovery also depended on experimental conditions. The methods, biological results and error analysis herein may improve the understanding and optimization of DTT for use in various applications in neuroscience and medicine. Copyright © 2002 John Wiley & Sons, Ltd.
A framework based on spin glass models for the inference of anatomical connectivity from diffusion‐weighted MR data – a technical review
Authors: Mangin J.‐F. , Poupon C. , Cointepas Y. , Rivière D. , Papadopoulos‐Orfanos D. , Clark C. A. , Régis J. , Le Bihan D.
Published: December 2002

A family of methods aiming at the reconstruction of a putative fascicle map from any diffusion‐weighted dataset is proposed. This fascicle map is defined as a trade‐off between local information on voxel microstructure provided by diffusion data and a priori information on the low curvature of plausible fascicles. The optimal fascicle map is the minimum energy configuration of a simulated spin glass in which each spin represents a fascicle piece. This spin glass is embedded into a simulated magnetic external field that tends to align the spins along the more probable fiber orientations according to diffusion models. A model of spin interactions related to the curvature of the underlying fascicles introduces a low bending potential constraint. Hence, the optimal configuration is a trade‐off between these two kind of forces acting on the spins. Experimental results are presented for the simplest spin glass model made up of compass needles located in the center of each voxel of a tensor based acquisition. Copyright © 2002 John Wiley & Sons, Ltd.