bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reversible addition–fragmentation chain‐transfer graft polymerization of styrene: Solid phases for organic and peptide synthesis
Authors: Barner Leonie , Zwaneveld Nik , Perera Senake , Pham Yen , Davis Thomas P. 
Published: October 2002

AbstractThe γ‐initiated reversible addition–fragmentation chain‐transfer (RAFT)‐agent‐mediated free‐radical graft polymerization of styrene onto a polypropylene solid phase has been performed with cumyl phenyldithioacetate (CPDA). The initial CPDA concentrations range between 1 × 10−2 and 2 × 10−3 mol L−1 with dose rates of 0.18, 0.08, 0.07, 0.05, and 0.03 kGy h−1. The RAFT graft polymerization is compared with the conventional free‐radical graft polymerization of styrene onto polypropylene. Both processes show two distinct regimes of grafting: (1) the grafting layer regime, in which the surface is not yet totally covered with polymer chains, and (2) a regime in which a second polymer layer is formed. Here, we hypothesize that the surface is totally covered with polymer chains and that new polymer chains are started by polystyrene radicals from already grafted chains. The grafting ratio of the RAFT‐agent‐mediated process is controlled via the initial CPDA concentration. The molecular weight of the polystyrene from the solution (PSfree) shows a linear behavior with conversion and has a low polydispersity index. Furthermore, the loading of the grafted solid phase shows a linear relationship with the molecular weight of PSfree for both regimes. Regime 2 has a higher loading capacity per molecular weight than regime 1. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4180–4192, 2002
Structural characterization and gas‐transport properties of brominated matrimid polyimide
Authors: Guiver Michael D. , Robertson Gilles P. , Dai Ying , Bilodeau François , Kang Yong Soo , Lee Kwi Jong , Jho Jae Young , Won Jongok 
Published: October 2002

AbstractThe commercial polyimide Matrimid was modified by bromination for the purpose of improving its membrane‐transport properties as a gas‐separation material and providing functional group reactivity for further modifications. The unmodified and brominated polymers were characterized by elemental analysis and one‐dimensional and two‐dimensional NMR, which revealed that one bromine atom per repeat unit was incorporated regioselectively onto the indane aromatic ring. The thermal and physical properties of the polymers before and after bromination were also investigated. The gas‐transport properties of the unmodified and brominated polymers were compared. © 2002 Government of Canada. Exclusive worldwide publication rights in the article have been transferred to Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4193–4204, 2002
Synthesis and properties of amine‐containing poly(arylene ether sulfone) as an anion‐exchange matrix
Authors: Son Won‐Keun , Song Hea‐Young , Kim Sang‐Hern , Kim Hyung‐Joong , Kim Whan‐Gi 
Published: October 2002

AbstractPoly(arylene ether sulfone) (PSF), showing good thermal stability and excellent mechanical properties, was synthesized as an anion‐exchange matrix. It was synthesized by the condensation polymerization between bisphenol A and 4,4′‐dichlorodiphenylsulfone. 1°‐Amine‐containing poly(arylene ether sulfone) (1°‐APSF) was synthesized by the reduction reaction of a nitrated PSF. Then, it was transferred to 3°‐amine‐containing poly(arylene ether sulfone) (3°‐APSF) by the alkylation of the amine of 1°‐APSF. The properties of PSF, 1°‐APSF, and 3°‐APSF were investigated by Fourier transform infrared, 1H NMR spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. The introduction of the 3°‐amine group into PSF increased the glass‐transition temperature but decreased thermooxidative stability. The ion‐exchange capacities of 1°‐APSF and 3°‐APSF were shown to be 2.24 and 2.86 mequiv/g, respectively. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4281–4287, 2002
New polymer syntheses. CXI. Aliphatic polyesters by the ring‐opening polycondensation of glutaric anhydride with ethylene or trimethylene carbonate
Authors: Kricheldorf Hans R. , Petermann Oliver 
Published: October 2002

AbstractSeveral polycondensations of ethylene carbonate with succinic anhydride or glutaric anhydride (GA) were conducted in bulk. Low molar mass polyesters were obtained with pyridine‐type catalysts and GA. Analogous polycondensations of trimethylene carbonate (TMC) and GA were successful when quinoline, 4‐(N,N‐dimethylamino)pyridine, or BF3 · OEt2 was used as a catalyst. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectra revealed the formation of cyclic oligoesters and polyesters by backbiting degradation. Monomer mixtures containing an excess of TMC yielded copoly(ester carbonate)s with number‐average molecular weights up to 16,000 Da. Analogous copoly(ester carbonate)s were obtained from TMC and 3,3′‐tetramethylene glutaric anhydride. Furthermore, combined polycondensation/ring‐opening polymerization reactions of TMC and GA with L‐lactide or ϵ‐caprolactone were studied. All copolymers were characterized by viscosity measurements and by IR, 1H, and 13C NMR spectroscopy. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4357–4367, 2002
Hydrogen bonding and hydrophobic interactions between [60]fullerenated poly(2‐hydroxyethyl methacrylate) and poly(1‐vinylimidazole) or poly(4‐vinylpyridine)
Authors: Goh H. W. , Goh S. H. , Xu G. Q. 
Published: October 2002

AbstractMiscible blends of poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly(1‐vinylimidazole) (PVI) have been formed in methanol/water (3/2 v/v) solutions. The incorporation of 0.6 wt % C60 into PHEMA leads to hydrophobic interactions and enhanced hydrogen bonding in miscible blends of [60]fullerenated poly(2‐hydroxyethyl methacrylate) (FPHEMA) with PVI. The incorporation of 2.6 wt % C60 into PHEMA increases its tendency to form interpolymer complexes with PVI. Interpolymer complexes are formed when FPHEMA samples containing 0.6, 1.4, and 2.6 wt % C60 are blended with poly(4‐vinylpyridine). The yields of the complexes increase with increasing C60 content in FPHEMA. Calorimetry and Fourier transform infrared spectroscopy studies suggest the importance of hydrophobic interactions in C60‐containing blends and complexes. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4316–4327, 2002
Anionic polymerization of methyl methacrylate initiated with molybdenum and tungsten chloride/organolithium/triisobutylaluminum systems
Authors: Ihara Eiji , Tanaka Shinsuke , Inoue Kenzo 
Published: October 2002

AbstractMolybdenum chloride (MoCl5 or 1a) and tungsten chloride (WCl6 or 1b)/phenyllithium (PhLi)/triisobutylaluminum (iBu3Al) systems were found to be quite effective for controlling the anionic polymerization of methyl methacrylate (MMA), affording high molecular weight poly(methyl methacrylate)s (PMMAs; number‐average molecular weight > 100,000) with narrow molecular weight distributions (weight‐average molecular weight/number‐average molecular weight < 1.25) quantitatively at 0 °C for 1 h in toluene. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF MS) analyses of PMMAs obtained with the 1a and 1b/organolithium (RM; n‐butyllithium, PhLi)/iBu3Al systems revealed that the initiation of MMA with the systems occurred by a nucleophilic attack of H− to the monomer. In addition, the MALDI‐TOF MS analyses indicated that the presence of iBu3Al was responsible for the controlled polymerization by improving the uniformity of the polymerization with respect to initiation and termination and by preventing a backbiting reaction. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 4302–4315, 2002
Effects of tanshinone I isolated from Salvia miltiorrhiza Bunge on arachidonic acid metabolism and in vivo inflammatory responses
Authors: Kim Sung Young , Moon Tae Cheol , Chang Hyeun Wook , Son Kun Ho , Kang Sam Sik , Kim Hyun Pyo 
Published: October 2002

AbstractArachidonic acid (AA) mainly released from the cell membrane by phospholipase A2 (PLA2) is converted to eicosanoids by the action of cyclooxygenase (COX) and lipoxygenase (LO). In order to find the specific inhibitors of AA metabolism especially PLA2 and COX‐2, 300 plant extracts were evaluated for their inhibitory activity on PGD2 production from cytokine‐induced mouse bone marrow‐derived mast cells in vitro. From this screening procedure, the methanol extract of Salvia miltiorrhiza was found to inhibit PGD2 production and the ethyl acetate subfraction gave the strongest inhibition of five subfractions tested. From this ethyl acetate subfraction, an activity‐guided isolation finally gave tanshinone I as an active principle. This investigation deals with the effects of tanshinone I on AA metabolism from lipopolysaccharide (LPS)‐induced RAW 264.7 cells and in vivo antiinflammatory activity. Tanshinone I inhibited PGE2 formation from LPS‐induced RAW macrophages (IC50 = 38 μM). However, this compound did not affect COX‐2 activity or COX‐2 expression. Tanshinone I was found to be an inhibitor of type IIA human recombinant sPLA2(IC50 = 11 μM) and rabbit recombinant cPLA2 (IC50 = 82 μM). In addition, tanshinone I showed in vivo antiinflammatory activity in rat carrageenan‐induced paw oedema and adjuvant‐induced arthritis. Copyright © 2002 John Wiley & Sons, Ltd.
Measurement of insulin sensitivity indices using 13C‐glucose and gas chromatography/combustion/isotope ratio mass spectrometry
Authors: Clapperton Allan T. , Coward W. Andrew , Bluck Leslie J. C. 
Published: October 2002

AbstractImportant aspects of glucose metabolism can be quantified by using the minimal model of glucose kinetics to interpret the results of intravenous glucose tolerance tests. The power of this methodology can be greatly increased by the addition of stable isotopically labelled tracer to the glucose bolus dose. This allows the separation of glucose disposal from endogenous glucose production and also increases the precision of the estimates of the physiological parameters measured. Until now the tracer of choice has been deuteriated glucose and the analytical technique has been gas chromatography/mass spectrometry (GC/MS). The consequence of this choice is that nearly 2 g of labelled material are needed and this makes the test expensive. We have investigated the use of 13C‐labelled glucose as the tracer in combination with gas chromatography/combustion/isotope ratio mass spectrometry (GC/C/IRMS) as the analytical technique. This methodology offers superior analytical precision when compared with the conventional method and so the amount of tracer used, and hence the cost, can be reduced considerably. Healthy non‐obese male volunteers were recruited for a standard intravenous glucose tolerance test (IVGTT) protocol but 6,6‐2H‐glucose and 1‐13C‐glucose were administered simultaneously. Tracer/tracee ratios were derived from isotope ratio measurements of plasma glucose using both GC/MS and GC/C/IRMS. The results of these determinations indicated that the two tracers behaved identically under the test protocol. The combination of these results with plasma glucose and insulin concentration data allowed determination of the minimal model parameters S*
g and S*
i. The parameter relating to insulin‐assisted glucose disposal, S*
i, was found to be the same in the two techniques, but this was not the case for the non‐insulin‐dependent parameter S*
g. Copyright © 2002 John Wiley & Sons, Ltd.
Structural characterization of chondroitin/dermatan sulfate oligosaccharides from bovine aorta by capillary electrophoresis and electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry
Authors: Zamfir Alina , Seidler Daniela G. , Kresse Hans , Peter‐Katalinić Jasna 
Published: October 2002

AbstractAn Erratum for this article has been published in Rapid Communications in Mass Spectrometry 17(3) 2003, 265An analytical approach based on high‐performance capillary electrophoresis (CE) in conjunction with electrospray ionization quadrupole time‐of‐flight tandem mass spectrometry (ESI‐QTOF‐MS/MS) has been developed for providing the basis to obtain new insights into the domain structure of the glycosaminoglycan (GAG) moiety of proteoglycans. The feasibility and performance of the off‐line CE/ESI‐QTOF‐MS approach in GAG oligosaccharide analysis were assessed by screening a chondroitin/dermatan sulfate (DS) oligosaccharide mixture obtained from bovine aorta by enzymatic depolymerization by chondroitin B lyase. The CS/DS mixture was analyzed by CE using 50 mM ammonium acetate, pH 12.0, dissolved in aqueous methanol (2:3; v/v), as a CE carrier. Structural identification of the GAG components was achieved using off‐line CE/nanoESI‐QTOF‐MS and‐MS/MS experiments. ESI‐QTOF instrumental parameters were found to play an important role in the MS screening of the CE‐separated GAG species. By optimizing the ESI conditions, oligosaccharides differing in chain length and degree of sulfation could be detected. The building block composition, the size of the carbohydrate chain, as well as structural features of the repeating HexA‐GalNAc, HexA‐GalNAc(S) units, have been determined using MS/MS by applying collision‐induced dissociation at low energies. Cleavage of GAG chains by chondroitin B lyase occurs with formation of structural markers useful for identification of IdoA‐containing domains. Copyright © 2002 John Wiley & Sons, Ltd.
Effect of water treatment on analyte and matrix ion yields in matrix‐assisted time‐of‐flight secondary ion mass spectrometry: the case of insulin in and on hydroxycinnamic acid
Authors: Szymczak Wilfried , Wittmaack Klaus 
Published: October 2002

AbstractA systematic study was performed to identify the origin of surprisingly high analyte‐to‐matrix yield ratios recently observed in time‐of‐flight secondary ion mass spectrometry (TOF‐SIMS) analysis of oligo‐ and polypeptides mixed in matrices of α‐cyano‐4‐hydroxycinnamic acid (4HCCA). Several sets of samples of porcine insulin in 4HCCA (1:3100 molar) were prepared from liquid solutions by a nebuliser technique, with more than one order of magnitude variation in sprayed material (substrate silicon). Following different periods of storage in air and/or vacuum as well as exposure to high‐purity water, TOF‐SIMS analysis was performed under oblique impact of 22 keV SF5+. Treatment with water involved either deposition of a droplet covering the whole sample for times between 1 and 20 min or spraying with water in droplet equivalent quantities. The analyte and matrix molecules were detected as protonated molecules (insulin also in doubly protonated form). Even the as‐prepared samples usually showed insulin‐to‐4HCCA yield ratios exceeding the molar ratio of the mixed material. Upon ageing in vacuum the matrix ion yields remained constant but the analyte yields decreased, partly due to break‐up of intrachain disulfide bonds. Water treatment resulted in a pronounced decrease in the 4HCCA yield, typically by a factor of five, in parallel with an increase of the insulin yield, by up to a factor of four. Evidence is provided that these changes occur concurrently with a partial dissolution of 4HCCA at the sample surface. The enhanced insulin yield was not correlated with the Na+ yield. The typically 20‐fold increase in the insulin‐to‐4HCCA yield ratio, generated by water exposure of the samples, provides the explanation for the high yield ratios observed previously with water‐treated samples. Spraying with water or repeated exposure to water droplets caused a pronounced degradation of the insulin parent yields in combination with an increasing appearance of signals due to the B‐ and A‐chains of insulin. To clarify the issue of surface segregation, a few samples were prepared by spraying acetone‐diluted solutions of insulin on previously deposited layers of 4HCCA. Whereas the insulin yields from as‐prepared samples were rather low, the yields observed after water treatment were comparable with those observed with samples of insulin in 4HCCA. The results suggest that a large amount of insulin is present at the surface of samples prepared from liquid mixtures of insulin in 4HCCA. With both methods of sample preparation, however, high secondary ion yields of insulin were only obtained after exposure of the samples to water. The chemical changes responsible for this beneficial effect still need to be identified. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of wheat quality by mass spectrometry and multivariate data analysis
Authors: Gottlieb David Mark , Schultz Jakob , Petersen Marianne , Nesic Ljiljana , Jacobsen Susanne , Søndergaard Ib 
Published: October 2002

AbstractMultivariate analysis has been applied as support to proteome analysis in order to implement an easier and faster way of data handling based on separation by matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry. The characterisation phase in proteome analysis by means of simple visual inspection is a demanding process and also insecure because subjectivity is the controlling element. Multivariate analysis offers, to a considerable extent, objectivity and must therefore be regarded as a neutral way to evaluate results obtained by proteome analysis.Proteome analysis of storage proteins from the wheat gluten complex based on two‐dimensional electrophoresis and analysis of the N‐terminal sequence has revealed a protein homologous to γ‐gliadins, tentatively associated with quality and within the molecular weight range 27–35 kDa. Further examinations of gliadin data based on mass spectrometry revealed that quality among wheat varieties could be determined by means of principal component analysis. Further examinations by interval partial least squares made it possible to encircle an overall optimal molecular weight interval from 31.5 to 33.7 kDa. The use of multivariate analysis on data from mass spectrometry has thus shown to be a promising technique to minimize the number of two‐dimensional gels within the field of proteome analysis. Copyright © 2002 John Wiley & Sons, Ltd.
Mass spectra of 1,3,5‐triarylpentane‐1, 5‐diones: formation and decomposition of pyrilium cation from the molecular ion
Authors: MPOH Godefroy Elanga , Tapsoba Edouard , Nébié Roger Charles , Bonzi‐Coulibaly Yvonne Libona , Sié Faustin Sib 
Published: October 2002

AbstractElectron impact mass spectra of 1,3,5‐triarylpentane‐1,5‐diones are reported. All compounds studied show a tendency to eliminate a water molecule and also the elements of [H3O] before fragmentation to smaller ions. The [H3O] loss proceeds via loss of water to form a pyran ion, which subsequently eliminates a hydrogen atom to form the stable pyrillium cation. Copyright © 2002 John Wiley & Sons, Ltd.
Investigation of an enhanced resolution triple quadrupole mass spectrometer for high‐throughput liquid chromatography/tandem mass spectrometry assays
Authors: Yang Liyu , Amad Ma'an , Winnik Witold M. , Schoen Alan E. , Schweingruber Hans , Mylchreest Iain , Rudewicz Patrick J. 
Published: October 2002

AbstractTriple quadrupole mass spectrometers, when operated in multiple reaction monitoring (MRM) mode, offer a unique combination of sensitivity, specificity, and dynamic range. Consequently, the triple quadrupole is the workhorse for high‐throughput quantitation within the pharmaceutical industry. However, in the past, the unit mass resolution of quadrupole instruments has been a limitation when interference from matrix or metabolites cannot be eliminated. With recent advances in instrument design, triple quadrupole instruments now afford mass resolution of less than 0.1 Dalton (Da) full width at half maximum (FWHM). This paper describes the evaluation of an enhanced resolution triple quadrupole mass spectrometer for high‐throughput bioanalysis with emphasis on comparison of selectivity, sensitivity, dynamic range, precision, accuracy, and stability under both unit mass (1 Da FWHM) and enhanced (≤0.1 Da FWHM) resolution. The advantage of enhanced resolution was demonstrated in the case of mometasone with polypropylene glycol (PPG) interference. At unit mass resolution, the transmitted precursor ion from the first quadrupole contained not only protonated molecules from mometasone, but also PPG interference. At enhanced resolution only selected mometasone peaks were transmitted, and no interference from PPG was detected. Sensitivity of the instrument was demonstrated with 10 femtograms of descarboethoxyloratadine injected on‐column, for which a signal‐to‐noise (S/N) ratio of 24 was obtained for MRM chromatograms at both unit and enhanced resolution. Absolute signals obtained at enhanced resolution were about one‐third those obtained at unit mass resolution. However, S/N was maintained at enhanced resolution due to the proportional decrease in noise level. Finally, the stability of the instrument operating at enhanced resolution was demonstrated during an overnight 17 h period that was used to validate a liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay for the quantitation of loratadine and descarboethoxyloratadine in human plasma. Assay performances (dynamic range, correlation coefficients for standard curves, precision and accuracy for QC samples) under unit and enhanced resolution were both within current pharmaceutical and regulatory guidelines demonstrating the stability of the mass spectrometer operating at enhanced resolution for typical bioanalytical high‐throughput applications. Copyright © 2002 John Wiley & Sons, Ltd.
Mass spectrometric study of some 4‐pyrimidine carboxylic acids
Authors: Jovanović Bratislav Ž. , Perić‐Grujić Aleksandra A. , Marinković Aleksandar D. , Vajs Vlatka V. 
Published: October 2002

AbstractMass spectrometry has been applied in order to study the main fragmentation routes of some 4‐pyrimidene carboxylic acids. Differences in fragmentation were caused by the nature of the substituent in position 2 of the pyrimidine ring, while the methyl group in position 1, 3 or 6 did not influence the fragmentation route. Copyright © 2002 John Wiley & Sons, Ltd.
A robust micro‐electrospray ionization technique for high‐throughput liquid chromatography/mass spectrometry proteomics using a sanded metal needle as an emitter
Authors: Guzzetta Andrew W. , Thakur Rohan A. , Mylchreest Iain C. 
Published: October 2002

AbstractA 60 µm internal diameter (i.d.) stainless‐steel needle was adapted to the orthogonal ESI probe (µESI) of a commercial ion trap mass spectrometer, and used for capillary liquid chromatography/tandem mass spectrometry (LC/MS/MS) protein identification experiments. The modification allows for the use of nitrogen sheath gas which helps in the nebulization at LC flow rates exceeding 500 nL/min and eliminates problems caused by liquid junctions commonly used to initiate nanospray ionization (NSI). A comparison is made between the performance of a 75 µm i.d. column with a 15 µm pulled glass tip using a liquid junction, and that of a 150 µm i.d. column using the new µESI device. The combination of the 150 µm i.d. column and µESI gave sensitivity close to that of NSI (250 attomoles horse heart myoglobin digest on column), and proved to be more robust than the standard pulled glass tips of similar i.d. No evidence of metal needle catalyzed oxidation of methionine was observed during analysis of the tetrapeptide MRFA under a range of test conditions. Phosphorylated peptides in a β‐casein tryptic digest were also successfully identified using the µESI interface with a steel needle. In addition it was found that a mild sanding of the metal needle tip improved spray performance. Copyright © 2002 John Wiley & Sons, Ltd.