bluuebunny/crossref_metadata_2025_split huggingface dataset:
The early glycation products of the Maillard reaction: mass spectrometric characterization of novel imidazolidinones derived from an opioid pentapeptide and glucose
Authors: Roščić Maja , Versluis Cornelis , Kleinnijenhuis Anne J. , Horvat Štefica , Heck Albert J. R. 
Published: August 2002

AbstractGlucose‐substituted imidazolidinones related to the endogenous opioid peptide leucine‐enkephalin have been investigated using fast atom bombardment tandem mass spectrometry (FAB‐MS/MS) and electrospray ionization tandem mass spectrometry (ESI‐MS/MS). In addition to Amadori compounds, the studied imidazolidinones represent a novel type of the early glycation products formed in the Maillard reaction. To obtain insight into the fragmentation behavior of these carbohydrate‐peptide adducts, we also studied synthetic precursors of the glucose‐substituted imidazolidinones as well as the corresponding isopropylidene derivatives. The collision‐induced dissociation (CID) spectra of [M + H]+ ions of all these imidazolidinones have been compared. Detailed analysis showed that fragmentation of each compound generates two ions at m/z 566 and m/z 598 which are characteristic and undoubtedly confirm the imidazolidinone‐type structure. These two significant ions were identified as the M + 10 and M + 42 modifications of the N‐terminus of the parent opioid pentapeptide effected by the carbohydrate moiety. Furthermore, the ion at m/z 178 is identified as the M + 42 modification of the immonium ion of the N‐terminal amino acid (tyrosine) also effected by the carbohydrate moiety. They can be used as diagnostic ions for imidazolidinone‐type compounds in studying the Maillard reaction. Thus, we have demonstrated the utility of FAB‐MS/MS and ESI‐MS/MS in the structural determination and identification of such novel peptide‐carbohydrate adducts, useful in understanding the details of the mechanism of non‐enzymatic glycation in vivo. Copyright © 2001 John Wiley & Sons, Ltd.
Fragmentation mechanism of novel compounds: 3,3‐dichloro‐1‐[2‐(2,2‐dichloro‐1‐oxoethylthio)phenyl]‐4‐(4‐methoxyphenyl)‐4‐(1‐phenylvinyl)‐2‐azetidinone and its derivatives
Authors: He Meiyu , Yuan Jinfang , He Zhenpei Yu Xiaoran , Wang Hongzhong , Zhou Xin , Jin Sheng 
Published: August 2002

AbstractElectron impact mass spectra of five new compounds are reported. Under electron impact conditions all five compounds yielded abundant fragment ions and lower abundances of molecular ions. Apart from the expected i‐and α‐cleavages, three additional unusual fragmentation processes were observed. The proposed fragmentation mechanisms were supported by D‐labeling experiments, accurate mass measurements, and mass‐analyzed ion kinetic energy spectrometry. Copyright © 2001 John Wiley & Sons, Ltd.
5‐Ethyl‐2‐mercaptothiazole as matrix for matrix‐assisted laser desorption/ionization of a broad spectrum of analytes in positive and negative ion mode
Authors: Raju N. Prasada , Mirza Shama P. , Vairamani M. , Ramulu A. Raghu , Pardhasaradhi M. 
Published: August 2002

AbstractA preliminary investigation of the use of 5‐ethyl‐2‐mercaptothiazole as matrix in matrix‐assisted laser desorption/ionization (MALDI) of a broad spectrum of analytes is reported. The analytes studied are substance P, insulin, β‐cyclodextrin, triacylglycerols of coconut oil and polypropylene glycol 2000 (PPG 2000). In the positive ion mass spectra of the matrix/analyte combinations, the formation of [M + H]+ and [M + cation]+ species were observed and compared with those obtained by using well‐established matrices such as α‐cyano‐4‐hydroxycinnamic acid, genticic acid, sinapinic acid and dithranol. In addition, the usefulness of this new matrix for MALDI in negative ion mode is also described using substance P and β‐cyclodextrin as examples. Copyright © 2001 John Wiley & Sons, Ltd.
Direct detection of polyaromatic hydrocarbons, estrogenic compounds and pesticides in water using desorption chemical ionisation membrane inlet mass spectrometry
Authors: Aggerholm Tenna , Lauritsen Frants R. 
Published: August 2002

AbstractThis paper describes the use of desorption chemical ionisation membrane inlet mass spectrometry (DCI‐MIMS) for the detection of a broad range of common contaminants in water. In addition, we discuss the advantages/disadvantages of two different types of chemical ionisation reagent gases, i‐butene (a Broensted acid reagent) and argon (a charge exchange reagent). We found that polyaromatic hydrocarbons was detectable at ppt levels, the estrogenic compounds diethyl phthalate and octylphenol at high ppt levels, steroid hormones at ppb levels, hydrophobic pesticides at low ppb levels, whereas hydrophilic pesticides and bisphenol A were not detectable at all. With the exception of the polyaromatic hydrocarbons and pentachlorophenol, none of the reported compounds have to our knowledge been detected previously by other MIMS systems. In most cases the Broensted acid reagent gave characteristic ions at high mass/charge ratio, whereas the charge exchange reagent gave less characteristic ions at low m/z ratio. However, the sensitivity was generally not as good with the Broensted acid reagent as with the charge exchange reagent, since the Broensted acid reagent, i‐butene, gave a large chemical background. Copyright © 2001 John Wiley & Sons, Ltd.
Electrospray ionization mass spectrometric investigation of ammonium ion complexes with anomeric 2,3‐O‐isopropylidene‐1α‐ and ‐1β‐D‐ribofuranosyl azides: anomeric and kinetic isotope effects in ammonium affinities
Authors: Kralj Bogdan , Kocjan Darko , Kobe Joz̆e 
Published: August 2002

Abstract[Methanol + ammonium acetate] solutions of anomeric 2,3‐O‐isopropylidene‐1α‐ and 1β‐ribofuranosyl azides were investigated by electrospray ionization mass spectrometry (ESI‐MS). The compounds included d6‐labeled and/or unlabeled isopropylidene groups that enable the identification of peaks characteristic of the ammonium‐attached monomeric (MNH4+), ammonium‐bound homodimeric ([M]2NH4+) and heterodimeric ([MNH4M1]+) complex ions in ESI mass spectra of solutions of a pair of compounds. The intensities of the product ion peaks obtained by the collisionally activated ammonium‐bound dimeric ions are related to the secondary isotope effect kα/kαd6 = 0.88 and kβ/kβd6 = 1.25 or to isotope plus anomeric effects kα/kβd6 = 1.43 and kβ/kαd6 = 0.59 in the ammonium affinities of these compounds. The calculations of solely anomeric effects in the ammonium affinities of α and β anomeric compounds obtained from the data presented previously give two series of values: kα/kβ = (kα/kαd6)(kαd6/kβ) = 1.49 and kαd6/kβd6 = (kαd6/kβ)(kβ/kβd6) = 2.12 or kα/kβ = (kα/kβd6)(kβd6/kβ) = 1.14 and kαd6/kβd6 = (kαd6/kα)(kα/kβd6) = 1.63. The disparities of these results indicate the different structures of hydrogen bonding in ammonium‐bound dimeric complexes which decompose to monomeric ions with different rate constants. Comparison of experimental results obtained by the qualitative approach of the kinetic method and ammonium affinities of these compounds calculated by the semi‐empirical molecular orbital method (AM1) show that the [MNH4M1]+ dimeric complex ions dissociate to the most stable MNH4+ and M1NH4+ monomeric ions. The obtained relative order of ammonium affinities of these compounds is: αd6 > α > β > βd6. Copyright © 2001 John Wiley & Sons, Ltd.
Negative ion clusters in self‐condensation of GeH4
Authors: Antoniotti Paola , Operti Lorenza , Rabezzana Roberto , Vaglio Gian Angelo , Guarini Alessandro 
Published: August 2002

AbstractFormation of negative ion clusters from GeH4 has been studied as a function of germane pressure, in the 25–450 mTorr range, by chemical ionisation mass spectrometry. At the lowest pressures, only the GeHn− (n = 0–3) ion family is formed, whilst at increasing pressures GemHn− (m = 1–9) ion clusters of increasing size are observed in the mass spectra. A variable contribution of the ions with different hydrogen content is observed as a function of the pressure of germane in all the GemHn− (m = 1–9) clusters. Increasing pressures induce a general increase of ion species with a low content of hydrogen atoms. In fact, at 450 mTorr, 38% of the ion current is due to the bare Gem− (m = 2–5) clusters and 83% to the sum of abundances of the GemHn− ions without hydrogen (n = 0) and with a number of hydrogen atoms not higher than the number of germanium atoms (n = 0–m). This trend suggests that a contribution of negative clusters to the deposition of the amorphous solid a‐Ge:H from gaseous systems containing GeH4, activated by radiolytic methods, can enhance the formation of solids with a low hydrogen content, which show better photoelectrical properties. Copyright © 2001 John Wiley & Sons, Ltd.
Capillary electrophoresis/electrospray ion trap mass spectrometry for the analysis of negatively charged derivatized and underivatized glycans
Authors: Gennaro Lynn A. , Delaney Jeannine , Vouros Paul , Harvey David J. , Domon Bruno 
Published: August 2002

AbstractThe increasing interest in the development of glycoproteins for therapeutic purposes has created a greater demand for methods to characterize the sugar moieties bound to them. Traditionally, released carbohydrates are derivatized using such methods as permethylation or fluorescent tagging prior to analysis by high performance liquid chromatography (HPLC), capillary electrophoresis (CE), or direct infusion mass spectrometry. However, little research has been performed using CE with on‐line mass spectrometry (MS) detection. The CE separation of neutral oligosaccharides requires the covalent attachment of a charged species for electrophoretic migration. Among charged labels which have shown promise in assisting CE and HPLC separation is the fluorophore 8‐aminonaphthalene‐1,3,6‐trisulfonic acid (ANTS). This report describes the qualitative profiling of charged ANTS‐derivatized and underivatized complex glycans by CE with on‐line electrospray ion trap mass spectrometry. Several neutral standard glycans including a maltooligosaccharide ladder were derivatized with ANTS and subjected to CE/UV and CE/MS using low pH buffers consisting of citric and 6‐aminocaproic acid salts. The ANTS‐derivatized species were detected as negative ions, and multiple stage MS analysis provided valuable structural information. Fragment ions were easily identified, showing promise for the identification of unknowns. N‐Linked glycans released from bovine fetuin were used to demonstrate the applicability of ANTS derivatization followed by CE/MS for the analysis of negatively charged glycans. Analyses were performed on both underivatized and ANTS‐derivatized species, and sialylated glycans were separated and detected in both forms. The ability of the ion trap mass spectrometer to perform multiple stage analysis was exploited, with MS5 information obtained on selected glycans. This technique presents a complementary method to existing methodologies for the profiling of glycan mixtures. Copyright © 2002 John Wiley & Sons, Ltd.
Determination of drug binding sites to proteins by electrospray ionisation mass spectrometry: the interaction of cisplatin with transferrin
Authors: Allardyce Claire S. , Dyson Paul J. , Coffey Jonathan , Johnson Neil 
Published: August 2002

AbstractCisplatin, cis‐[PtCl2(NH3)2], is known to bind to human serum transferrin, but the binding site remains a matter of some debate. Electrospray ionisation mass spectrometry has been used to characterise the interaction of cisplatin with transferrin. The studies indicate that cisplatin initially docks with, and subsequently bonds covalently to, the hydroxyl functional group of threonine 457, with the loss of HCl affording a transferrin‐O‐PtCl(NH3)2 adduct. Copyright © 2002 John Wiley & Sons, Ltd.
Electron capture dissociation of polypeptides using a 3 Tesla Fourier transform ion cyclotron resonance mass spectrometer
Authors: Polfer Nicolas C. , Haselmann Kim F. , Zubarev Roman A. , Langridge‐Smith Pat R. R. 
Published: August 2002

AbstractElectron capture dissociation (ECD) of polypeptides has been demonstrated using a commercially available 3 Tesla Fourier transform ion cyclotron resonance (FTICR) instrument. A conventional rhenium filament, designed for high‐energy electron impact ionisation, was used to effect ECD of substance P, bee venom melittin and bovine insulin, oxidised B chain. A retarding field analysis of the effective electron kinetic energy distribution entering the ICR cell suggests that one of the most important parameters governing ECD for this particular instrument is the need to employ low trapping plate voltages. This is shown to maximise the abundance of low‐energy electrons. The demonstration of ECD at this relatively low magnetic field strength could offer the prospect of more routine ECD analysis for the wider research community, given the reduced cost of such magnets and (at least theoretically) the greater ease of electron/ion cloud overlap at lower field. Copyright © 2002 John Wiley & Sons, Ltd.
Automatic Detection of Lung Cancers in Chest CT Images by the Variable N‐Quoit Filter
Authors: Miwa Tomoko , Kako Jun‐ichi , Yamamoto Shinji , Matsumoto Mitsuomi , Tateno Yukio , Iinuma Takeshi , Matsumoto Toru 
Published: August 2002

AbstractThe authors have developed the quoit filter, which is a kind of mathematical morphological filter, for automatic extraction of candidate pathological areas of lung cancer. The method has problems, however, in processing speed or extraction accuracy. To overcome these problems, this paper proposes variable quoit filtering, in which the filter size is adjusted flexibly according to the pathological shadow, and distance transformation with gray‐level weight is applied as preprocessing before the main filtering procedure. First, the performance of the method is analyzed using a model, and the effectiveness of the proposed method is shown. Then, trial applications to images of 82 actual cases (including 21 cancer areas) show that all of the cancer areas were correctly extracted. Compared to the conventional algorithm, the processing time is reduced to less than 1/20. © 2001 Scripta Technica, Syst Comp Jpn, 33(1): 53–63, 2002
Characterization of the Ziegler‐Natta olefin polymerization system: surface science studies on model catalysts
Authors: Kim Seong Han , Somorjai Gabor A. 
Published: August 2002

AbstractModern surface science techniques have been applied to the heterogeneous Ziegler‐Natta catalysis system, polymerizing α‐olefins to produce polyolefins, and revealed the correlation between the catalyst surface structure and polymer properties. Two types of thin films—TiClx/MgCl2 and TiCly/Au—were fabricated on an inert gold substrate, using chemical vapor deposition methods, to mimic the high‐yield catalysts of MgCl2‐supported TiCl4 and TiCl3‐based catalysts, respectively. Once activated with triethylaluminum (AlEt3) vapor, both catalysts were active for polymerization of ethylene and propylene in the absence of excess AlEt3. The model catalyst films were as active as the high‐surface‐area industrial catalysts. Both catalysts were terminated with chlorine at the surface but had different surface structures. The TiClx/MgCl2 film had a distribution of two structures: the dominant sites had the (001) basal plane of these halide crystallites and the minority sites had a non‐basal plane structure. The surface of the TiCly/Au film assumed only the non‐basal plane structure. These structural differences resulted in different tacticity of the polypropylene produced with these catalysts. The TiClx/MgCl2 catalyst produced both atactic and isotactic polypropylene, whereas the TiCly catalyst without the MgCl2 support produced exclusively isotactic polypropylene. The titanium oxidation states did not appear to be an important factor in determining the tacticity of the polypropylene. Copyright © 2001 John Wiley & Sons, Ltd.
Absolute energy calibration in an energy analyser (CMA) using elastically backscattered primary electrons: iterative method
Authors: Goto K. , Nissa Rahman N. , Jiang Y. Z. , Asano Y. , Shimizu R. 
Published: August 2002

AbstractEnergy calibration in an Auger electron analyser has been studied using elastically backscattered primary electrons (BPEs), with a feasibility of 15 meV(σ) for the kinetic energies of 10–1200 eV in which our improved cylindrical mirror analyser (CMA) has been used. An electron gun with a special tungsten cathode of reduced magnetic field and having unipotential was operated in constant emission current mode. This mode presents the well‐defined characteristics of the BPEs. Thus, the energy distribution of the BPEs and the shape and the peak position would be kept constant irrespective of the acceleration voltage of the BPEs. An iteration method (between the higher and lower energies) was employed to obtain the transfer coefficient of the CMA, i.e. a self‐consistent method with automatic corrections for the thermionic emission and the work functions. A convolution simulation of the CMA was examined to obtain the right peak position of the BPEs. It was found that the broader diameter of the BPE beams can be used in the calibration without any appreciable loss of accuracy. Copyright © 2002 John Wiley & Sons, Ltd.
Influence of surface composition and density on electron inelastic mean free paths in Ge
Authors: Lesiak B. , Jablonski A. , Zemek J. , Jiricek P. , Pavluch J. 
Published: August 2002

AbstractThe number of inelastic mean free path (IMFP) values for Ge available in the literature is limited. In the present work, elastic peak electron spectroscopy (EPES) was used to determine the IMFPs in native Ge oxide and sputtered Ge. The Ge surfaces are rough and differ in surface composition, the chemical bonding state of atoms at the surface and the density of the surface layer. Two analysers were used—a high‐resolution hemispherical analyser (ADES‐400) and a retarding field analyser (RFA)—for two experimental EPES procedures, one with a Cu standard (ADES‐400) and one without a standard (RFA).The aim of the present work was to verify the applicability of the EPES method to technological Ge surfaces. The EPES method was found to be a convenient tool for investigating IMFPs in such samples. The influence of varying surface composition, chemical state of atoms and density on the measured IMFPs resulting from EPES and the IMFPs resulting from the TPP‐2M and the G1 of Gries predictive formulae was analysed. Comparison between measured and predicted IMFPs for the same Ge surfaces, enclosing the estimate of the overall statistical and systematic error of the above methods, was made. The error in the IMFPs resulting from EPES due to accuracy of input parameters for the Monte Carlo algorithm was discussed. Copyright © 2002 John Wiley & Sons, Ltd.
Exploiting exceptions
Authors: Zastre Michael , Horspool R. Nigel 
Published: August 2002

AbstractA novel compiler optimization for loops is presented. The optimization uses exceptions to eliminate redundant tests that are performed when code is interpretively executed, as is the case with Java bytecode executed on the Java Virtual Machine. An analysis technique based on abstract interpretation is used to discover when the optimization is applicable. Copyright © 2001 John Wiley & Sons, Ltd.
[125 I]3β‐(4‐ethyl‐3‐iodophenyl)nortropane‐2β‐carboxylic acid methyl ester ([125I]EINT): A potent and selective radioligand for the brain serotonin transporter
Authors: Navarro H. A. , Xu H. , Zhong D. , Blough B. E. , Ross W. P. , Kuhar M. J. , Carroll F. I. 
Published: August 2002

AbstractThe binding characteristics of [125I]3β‐(4‐ethyl‐3‐iodophenyl)nortropane‐2β‐carboxylic acid methyl ester ([125I]EINT), a high‐affinity selective ligand for the serotonin transporter (5‐HTT), and its binding characteristics to rat brain membranes were determined. [125I]EINT binding to rat cerebral cortex membranes was saturable and reversible, and its specific binding represented approximately 90% of the total binding. [125I]EINT labeled a single site with Kd = 0.22 ± 0.03 nM and Bmax = 583 ± 38 fmol/mg protein. Kinetic analysis revealed a t1/2 for association and dissociation of 20 and 24 min, respectively. Pharmacological characterization of [125I]EINT confirmed its high specificity for the 5‐HTT. The pattern of brain region distribution in vivo of intravenously administered [125I]EINT indicated greater accumulation of the radioligand in 5‐HTT‐rich brain regions. However, the signal‐to‐background ratio was low. Thus, [125I]EINT appears to be a useful radioligand for studying the 5‐HTT in vitro, but it may not be a good in vivo ligand. Synapse 41:241–247, 2001. © 2001 Wiley‐Liss, Inc.
Why projects often fail, even with high cost‐contingencies
Authors: Kujawski Edouard 
Published: August 2002

AbstractIn this note we assume that the individual risks have been adequately quantified and the total project cost contingency adequately computed to ensure an agreed‐to probability or confidence level that the total project cost estimate will not be exceeded. But even projects that implement such a process are likely to result in significant cost overruns and/or project failure if the project manager allocates the contingencies to the individual subsystems. The intuitive and mathematically valid solution is to maintain a project‐wide contingency and to distribute it to the individual risks on an as‐needed basis. Such an approach ensures cost‐efficient risk management, and projects that implement it are more likely to succeed and to cost less. We illustrate these ideas using a simplified project with two independent risks. The formulation can readily be extended to multiple risks. © 2002 Wiley Periodicals, Inc. Syst Eng 5: 151–155, 2002
Indole synthesis by radical cyclization of o‐alkenylphenyl isocyanides and its application to the total synthesis of natural products
Authors: Tokuyama Hidetoshi , Fukuyama Tohru 
Published: August 2002

AbstractDevelopment of indole synthesis by tin‐mediated radical cyclization of o‐alkenylphenyl isocyanide is described. Upon heating o‐alkenylphenyl isocyanide in the presence of tri‐n‐butyltin hydride and AIBN, 2‐stannyl‐3‐substituted indole was formed via 5‐exo‐trig cyclization of the imidoyl radical intermediate. After acidic workup, 3‐substituted indoles were isolated. For substrates bearing simple alkyl groups, a substantial amount of tetrahydroquinoline derivatives were generated through 6‐endo‐trig cyclization. This undesired cyclization was suppressed by using an excess amount (five equivalents based on o‐alkenylphenyl isocyanide) of ethanethiol instead of tri‐n‐butyltin hydride. The 2‐stannylindole intermediates proved to be a suitable substrate for Stille coupling, giving 2,3‐disubstituted indoles in a one‐pot procedure. In addition, the 2‐stannylindole intermediates could be converted to 2‐iodoindoles by treatment with iodine or N‐iodosuccinimide. The 2‐iodoindoles thus obtained served as good substrates for Heck reactions, Stille couplings, Suzuki couplings, and palladium‐mediated carbonylations, to afford a variety of 2,3‐disubstituted indoles. The utility of this protocol was demonstrated by application to synthetic studies on gelsemine and discorhabdin A, and the total synthesis of an aspidosperma alkaloid, (–)‐vindoline. © 2002 The Japan Chemical Journal Forum and John Wiley & Sons, Inc. Chem Rec 2: 37–45, 2002
Reflections on the discovery of nature’s pathways to vitamin B12
Authors: Scott A. Ian 
Published: August 2002

AbstractThe chronology of the discoveries along the pathway of vitamin B12 biosynthesis is reviewed from a personal perspective, including discussion of the most recent finding that two pathways to B12 exist—one aerobic and one anaerobic—which differ mainly in the ring contraction mechanisms which convert porphyrin to corrin. © 2001 John Wiley & Sons, Inc. and The Japan Chemical Journal Forum Chem Rec 1:212–227, 2001