bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the alcohol denaturants denatonium benzoate (bitrex) and diethyl phthalate by direct flow injection APCI‐MS analysis
Authors: Alvarez‐Piñeiro Ma Elena , De Alda‐Villaizán Ma Joséa López , Paseiro‐Losada Perfecto , Lage‐Yusty Ma Asunción 
Published: May 2005

AbstractThe recently developed tandem technique, mass spectroscopy with atmospheric‐pressure chemical ionization (APCI‐MS) coupled with direct flow injection, was applied to the determination of Bitrex (denatonium benzoate) and diethyl phthalate in ethanol. The compounds were indentified from their total‐ion chromatograms(m/z 50‐500) and, simultancously, quantified using selected‐ion chromatograms recorded at m/z 223 for diethyl phthalate and m/z 325 for Bitrex. Operating conditions were optimized for soft ionization (positive ion‐mode) with fragmentation limited to that necessary for analyte identification, which was by the external‐standard method. Calibration curves were rectilinear in the concentration rages 2‐30 μg ml−1 (Bitrex) and 0.075‐1.2% v/v (diethyl phthalate); measurement precision (RSDs were 11.48% for Bitrex and 2.22% for diethyl phthalate), and detection limits (0.017 μg ml−1 and 0.010% v/v, respectively) were adequate for simiultaneous quantitation and with high sensitivity. The lack of any sample pretreatment and the use of flow‐injection analysis meant that the procedure was moere straightforward and rapid than previously reported methods.
Pressure effects on relative retention in capillary gas‐liquid chromatography
Authors: Berezkin Victor G. , Korolev Alexander A. , Malyukova Irina V. 
Published: May 2005

AbstractEquations have been obtained for the dependence of relative retention and retention indexes on average column pressure. The equations suggested conform well with experimental data. It was shown that limiting value of relative retention (at the pressure approaches zero) is an invariant retention value. The nature of the stationary liquid phase used and its film thickness have a substantial influence on the dependence of relative retention and capacity factor on the pressure.
Analytical approach in diagnosis of inherited metabolic diseases: Maple syrup urine disease (MSUD) – simultaneous analysis of metabolites in urine by enantioselective multidimensional capillary gas chromatography‐mass spectrometry (enantio‐MDGC‐MS)
Authors: Podebrad Frank , Heil Martin , Leib Saandra , Geier Bernhard , Beck Thomas , Mosandl Armin , Sewell Adrian C. , Böhles Hans 
Published: May 2005

AbstractMaple Syrup Urine disease (USUD) is an autosomal recessive inherited metabolic disorder of branched‐chain amino acid (L‐valin, L‐leucine, and L‐isoleucine metabolism named after the characteristic smell of affected patients urine. MSUD is caused by a deficiency of the branched‐chain α‐keto acid dehydrogenase compex resulting in an accumulation of branched‐chain aamino acids and the corresponding α‐keto‐and α‐hydroxy acids in blood, urine and cerebrospinal fluid causing neurological damage and mental retardation. The enantioselective analysis of chiral MSUD metabolites and analysis of achiral compounds as corresponding N,O‐methoxycarbonyl methyl esters by derivatization with methyl chloroformate (MCF) has been achieved simultaneusly by enantioselective multidimensional gas chromatography‐mass spectrometry using heptakis (2,3‐di‐O‐methyl‐6‐O‐tert‐butyl‐dimethyl‐silyl)‐β‐cyclodextrin as chiral stationary phase. Derivatization with MCF allows the analysis of the structurally different metabolitetes such as branched‐chain‐carboxylic‐, α‐oxo‐, α‐hydroxy‐ and α‐amino acids in a single chromaatographic run. Mass selective detection immensely improves the unequivocaaal identification of metabolites even when they occur as trace compound. The described method allows a reliable screening of MSUD metabolites in patients' urine without time consuming sample preparation and is also suitable for label enrichment analysis without any methodical changes. During this investigation urine sample from three MSUD paatients were analyzed.
Automated derivatization for on‐line solid‐phase extraction‐gas chromatography; phenolic compounds
Authors: Louter Arjan J. H. , Jones Philo A. , Jorritsma J. David , Vreuls Jolan J. , Brinkman Udo A. Th. 
Published: May 2005

AbstractAn automated system for derivaatization was coupled on‐line with solid‐phase extraction‐gas‐chromatography (SPE‐GC). The system was optimized for the determination of phenol and chlorinated phenols in aqueous samples. The test analytes were acetylated with acetic anhydride; proper buffering of the sample was a critical factor. Next, the phenol acetates were enriched on a SPE cartridge and transferred to a GC; two appraoaches were studied. In the first approach, the derivatives were enriched on disposable C18 cartridges (ASPEC type) and desorbed with methylacetate. Aan aliquot of the final eluate was injected on‐line the GC by means of a loop‐type interface. In the second approach, trace enrichment was performed on 10 × 2 mm i.d. LC‐type precolumn packed with polystyrenedivinylbenzene copolymer (PLRP‐S) this precolumn was dried with a mitrogen purge and the phenol acetates were desorbed with ethyl acetate which was injectedon‐line into the retention gap of the GC under partially concurrent solvent evaporation (PCSE) conditions. The Derivatization‐SPE‐GC system which was based on the loop‐type interface has the advantage of simplicity and easy operation, the main drawback is the impossibility to determine phenol acetates which elute prior to trichlorophenol acetates. With the derivatization‐SPE‐GC approach using PCSE‐based desorption, even the most volatile analyte of the test series, phenol acetate, can be determined successfully. The entire procedure, including the derivatization step, was fully automated and integrated in one set‐up. The precision data for the integrated on‐line derivatization‐SP‐FID system were fully satisfactory, with RSD values of 1–12 % at the 1 μg/1 level. When a sample volume of 2.2 ml was analyzed, The detection limits for the chlorinated phenol acetates were in the 0.1–0.3 μg/1 range.
Starburst dendrimer‐supported pseudostationary phases for electrokinetic chromatography
Authors: Tanaka Nobuo , Iwasaki Hironobu , Fukutome Takeshi , Hosoya Ken , Araki Takeo 
Published: May 2005

AbstractPseudo‐stationary phases for electrokinetic chromatography were prepared by the alkylation of starburst dendrimers (SBDs). The SBD‐supported pseudo‐stationary phase with dodecyl groups showed higher efficiency than short‐akyl derivatives, and maintained the hydrophobic property inthe presence of methanol. The dodecyl‐modified SBD provided wide migration time windows ar high methanol content to effect the separation of sixteen aromatic hydrocarbons, the priority pollutants designated by EPA, in 65% methanol. The selectivity of polymer‐supported pseudo‐stationary phase can be varied simply by changing the length of the alkyl groups. The dodecyl SBD showed relatively similar selectivity as sodium dodecyl culfate micelle, whereas short alkyl derivatives showed preference towards rigid and planar compounds based on the rigid and planar compounds based on the rigid polymer backbones. The selectivity of SBD‐supported pseudo‐stationary phases was dominated by the chain length of the alkyl groups, with the minor effect of the structure of the core and the generation of SBD where alkyl groups were attached.
Supercritical fluid extraction of kava lactones from Piper methysticum (kava) herb
Authors: Lopez‐Aila Viorica , Benedicto Janet 
Published: May 2005

AbstractSupercritical fluid extraction of kava lactones from Piper methysticum Forst. herb is described here. The extraction was performed with supercritical carbon dioxide alone and supercritical carbon dioxide modified with 15% ethanol, and the extracts were analyzed by gas chromatography/mass spectrometry. Seven lactones including: 7,8‐dihydrokavain; kavain; 5,6‐dehydrokavain; 5, 6, 7, 8‐tetrahydroyangonin; dihydromethysticin; yangonin; and methysticin were the major constituents in the SFE extract.
Chemical characterization of ozonated lignin solutions from corn (Zea mays) stalk and poplar (Populus deltoides) wood by capillary gas chromatography
Authors: Quesada Joaquín , Rubio Manual , Góamez Demetrio 
Published: May 2005

AbstractCorn (Zea mays) stalk and poplar (Populus deltoides) wood lignin was converted into monomeric aromatic compounds and short chain aliphatic carboxylic acids. The main reaction products were separated and identified using capillary gas chromatography‐mass spectrometry on an HP‐5 column. The compounds were considered as positively identified when their mass spectra and GC retention times agreed with those of authentic standard samples. The quantitative estimation of the identified reaction products was accomplished on an OV‐101 capillary column by gas chromatography‐FID using the internal standard method. Among the aromatic compounds, aldehydes (p‐hydroxybenzaldehyde, vanillin, and syringaldehyde), acids (p‐hydroxybenzoic, vanillic, 3,4‐dihydroxybenzoic, and syringic), and one phenol (hydroquinone) were determined. In addition, the aliphatic carboxylic acids: glycolic, oxalic, malonic, glyoxylic, butanedioic, glyceric, and malic acid were identified. All the calibration curves of the quantified compounds approximated to a straight line. For both corn stalk and poplar wood lignins, the major components were the aromatic aldehydes (71 and 64% of the characterized fraction, respectively), followed by the aliphatic carboxylic acids (20 and 21% of the characterized fraction, respectively).
Determination of acylglycerols in vegetable oil methyl esters by on‐line normal phase LC‐GC
Authors: Lechner Marion , Bauer‐Plank Christina , Lorbeer Eberhard 
Published: May 2005

AbstractAn on‐line LC‐GC method for the analysis of mono‐, di‐, and triacylglycerols in vegetable oil methyl esters has been developed. The concentrations of these components have turned out to be key parameters for the quality of diesel fuel substitutes. Separation of all classes of acylglycerols from the fatty acid methyl ester matrix is achieved by LC after acetylation of the hydroxyl groups. The acylglycerol fraction is transferred on‐line to GC, using the loop‐type interface and concurrent eluent evaporation. Quantification of mono‐, di‐, and triacylglycerols is performed by combining external calibration with internal standardization. Both recovery of the procedure and reproducibility of the quantitative results are evaluated.
Capillary gas chromatographic separation of C10–C12 secondary phenylalkanes on modified cyclodextrin stationary phases
Authors: Špáanik Ivan , Krupcik Jáan , Skacáani Ivan , De Zeeuw Jaap , Galli Mario , Sandra Pat 
Published: May 2005

AbstractThe separation of isomers and enantiomers of branched C10‐C12 phenylalkanes by gas chromatography on fused silica capillary columns coated with some modified β‐ and γ‐cyclodextrins was studied. It was shown that the separation of positional isomers of C10‐C12 phynylalkanes on modified cyclodextrin capillary columns is not better than that on a column coated with modified polyethylene glycol. Differences were found in the enantioselectivity of modified β‐ and γ‐cyclodextrins for the separation of C10‐C12 secondary phenylalkane enantiomers. While alkylderivatives of β‐CDs resolve enantiomers of 3‐phenylalkanes, alkyl derivatives of γ‐CD resolve enantiomers of 2‐phenylalkanes. Since shape selectivity factors of modified cyclodextrins have indicated no inclusion of the considered solutes in cyclodextrin cavities, enantioselective interactions most probably occur on the outer sphere of cyclodextrins.
Truncation of the ectodomain of the human insulin receptor results in secretion of a soluble insulin binding protein from transfected CHO cells
Authors: Ellis Leland , Sissom Janice , Levitan Alla 
Published: May 2005

AbstractThe Insulin receptor is an integral transmembrane glycoprotein comprised of two α‐(∼ 135kDa) and two β‐(∼ 95kDa) subunits, which is synthesized as a single polypeptide chain precursor (αβ). The primary sequence of the human insulin receptor (hIR) protein, deduced from the nucleotide sequence of cloned human placental mRNAs, predicts two large domains (929 and 403 residues) on either side of a single membrane spanning domain (23 residues); each of these major domains has a distinct function (insulin binding and protein/tyrosine kinase activity, respectively). To experimentally test this deduced topology, and to explore the potential for independent domain function by the hIR extracellular domain, we have constructed an expression plasmid encoding an hIR deletion mutant which is truncated 8 residues from the beginning of the predicted transmembrane domain (i.e., 921 residues). This domain of the hIR is in fact processed into α‐and truncated β‐subunits and secreted with high efficiency from transfected CHO cell lines which express this mutant hIR, and the protein accumulates as an (αβ)2 dimer in the medium. This molecule is recognized by a battery of 13 monoclonal antibodies to epitopes on the IR extracellular domain, four of which block insulin binding and two of which require the native conformation of the IR for recognition. Further, this domain, binds insulin with an apparent dissociation constant comparable to that of the wild‐type hIR. However, the secreted dimmer displays a linear Scatchard plot, while that of the wild‐type membrane‐associated hIR curvilinear. These results, together with previous results with a soluble derivative of the hIR cytoplasmic protein/tyrosine kinase domain, are consistent with the deduced topology. The IR is indeed comprised of two large soluble domains connected by a single membrane spanning domain, which on the one hand act concert upon ligand binding (insulin‐dependent activation of the protein/tyrosine kinase) to initiate the insulin response in cells, but on the other hand are each capable of autonomous function (ligand binding and protein/tyrosine kinase activity, respectively).
The design and synthesis of mimetics of peptide β‐turns
Authors: Kahn Michael , Wilke Susanne , Chen Barbara , Fujita Kagari , Lee Yu‐Hwei , Johnson Michael E. 
Published: May 2005

AbstractThe synthesis of an 11 membered ring bis‐lactam, a system which is designed as a conformationally restricted mimetic of type I and II β‐turns is described. Computer assisted molecular modeling was used to compare the predicted low energy conformers of the turn mimetic with idealized type I and type II turn structures. Initial computation analysis indicates that the basic ring structure will provide an excellent foundation for the development of variety of β‐turn mimetics.
Anhydroelastase: Enhanced affinity toward product‐type ligands revealed by affinity chromatography
Authors: Kumazaki Takashi , Kobayashi Masatomo , Ishii Shin‐ichi 
Published: May 2005

AbstractAnhydroelastase was effectively isolated by a single operation of affinity chromatography from a complex mixture produced by phenylmethylsulfonylation and alkaline treatment of porcine pancreatic elastase. The adsorbent used for the chromatography was 6‐aminohexanoyl‐trialanine, which corresponds to a product of elastase action, immobilized on Sepharose 4B. Successful resolution by the operation indicated that this immobilized ligand possesses the highest affinity for anhydroelastase among various proteins including regenerated elastase in the mixture. Comparative affinity chromatography on immobilized anhydroelastase and on immobilized native elastase further confirmed the stronger interaction of anhydroelastase with the product‐type peptides. Immobilized anhydroelastase was also found to be useful in the purification and search for naturally occurring proteinase inhibitors.
Contribution of antigen processing to the recognition of a synthetic peptide antigen by specific T cell hybridomas
Authors: Boyer Michel , Novak Zuzana , Fotedar Arun , Singh Bhagirath 
Published: May 2005

AbstractMost antigens recognized by T cells require unfolding or partial degradation (processing) followed by association with Major Histocompatibility Complex (MHC) molecules. We examined the processing requirements for the presentation of antigen to two T cell hybridomas which recognize the α‐helical synthetic polypeptide antigen Poly 18, Poly [EYK(EYA)5], in association with I‐Ad. Hybridoma A.1.1 responds to EYK(EYA)4 as the minimum antigenic sequence while hybridoma B.1.1 recognizes (EYA)5 sequence. It was found that these hybridomas responded to Poly 18 and to minimum peptide sequences presented by glutaraldehyde and chloroquine treated antigen presenting cells (APC), suggesting that antigen processing is not a requirement for the activation of these cells. The reactivity pattern of hybridoma B.1.1 in the presence of glutaraldehyde fixed APC revealed that antigens containing lysine were presented with much less efficiency than antigens without lysine, suggesting an interaction of these residues with the antigen presenting cell surface. We discuss the possibility that alanine residues in the α‐helical Poly 18 form a hydrophobic ridge which may be required for appropriate interaction between antigen, the T cell receptor, and MHC molecules.
Transition of environmental polarity of tyrosine‐76 of Trimeresurus flavoviridis phospholipase A2 upon active site ligand binding
Authors: Sakai Hironori , Oda Naoko , Kohzuma Takushi , Liu Song‐Yuan , Ohno Motonori , Kihara Hiroshi 
Published: May 2005

AbstractModification of Trmeresurus flavoviridis phospholipase A2 with a 5‐fold molar excess of tetranitromethane produced 40% active mononitrotyrosyl phospholipase A2 in which Try‐76 was specifically nitrated. This is in contrast to the case of mammalian pancreatic phospholipases A2 where Tyr‐70 but not Tyr‐76 was nitrated. When Ca2+ was bound to T. flavoviridis mononitrotyrosyl phospholipase A2, nitrated tyrosine (Tyr)NO2‐76 moved from a less polar site to a polar site with the decrease of the pKa value of its hydroxyl group. Nitration of Tyr‐76 did not influence the binding affinity to Ca2+. Addition of laurylphosphorylcholine to mononitrotyrosyl phospholipase A2 in the presence of Ca2+ caused the movement of Try(NO2)‐76 from a polar environment to a less polar environment with the rise in the pKa value. Tyrosine‐76 is located in the site whose environmental polarity is affected by the binding of the ligands to the active site. As Tyr‐76 is located in the site not proximal to the active site, it could be assumed that the conformational change induced by the binding of the ligands extends to the region remote from the active site in T. flavoviridis phospholipase A2. This might provide evidence of long‐range diffusional coupling between remote sites in the noncooperative globular protein.
A subsequence‐specific DNA‐binding domain resides in the 13 kDa amino terminus of the bacteriophage Mu transposase protein
Authors: Tolias Peter P. , DuBow Michael S. 
Published: May 2005

AbstractWe have previously reported that the 13kDa amino terminus of the 70 kDa bacteriophage D108 transposase protein (A gene product) contains a two‐component, sequence‐specific DNA‐binding domain which specifically binds to the related bacteriophage Mu's right end (attR) in vitro. To extend these studies, we examined the ability of the 13 kDa amino terminus of the Mu transposase protein to bind specifically to Mu attR in crude extracts. Here we report that the Mu transposase protein also contains a Mu attR specific DNA‐binding domain, located in a putative α‐heix‐turn‐α‐helix region, in the amino terminal 13 kDa portion of the 70 kDa transposase protein as part of a 23 kDa fusion protein with β‐lactamase. We purified for this attR‐specific DNA‐binding activety and ultimately obtained a single polypeptide of the predicated molecular weight for the A′—′bla fusion protein. We found that the pure protein bound to Mu attR site in a different mannar compared with the entrie Mu tranposase protein as determined by DNase I‐footpriting. Our results may suggest the presence of a potential of a potential primordial DNA‐binding site (5′‐PuCGAAA‐3′) located several times within attR, at the ends of Mu and D108 DNA, and at the extremities of other prokaryotic class II elements that catalyze 5 base pair duplications at the site of element insertion. The dissection of the functional domains of the related phage Mu and D108 transposase provide clues to the mechanism and evolution of DNA transposition as a mode of mobile gentic element propagation.
The conformation of core oligosaccharides from Escherichia coli and Salmonella typhimurium lipopolysaccharides as predicted by semi‐empirical calculations
Authors: Jansson Per‐Erik , Wollin Ralfh , Bruse Gert W. , Lindberg Alf A. 
Published: May 2005

AbstractThe preferred conformation of the hexose and heptose regions of core saccharides from Enterobacteriaceae lipopolysaccharides was calculated. The Hard Sphere Exo Anomeric (HSEA) approach was used and the minimum energy conformation of the Salmonella typhimurium and Escherichia coli R1, R2, R3, R4 and K12 cores calculated. The results indicate that most of the cores are sterically crowded, with small degrees of freedom, and that the hexose and heptose parts from two separate regions. The core structures exhibit a ‘front’‐side and a ‘back’‐side, the former being similar for all the structures and latter being characteristic for each core type.
Definition of the phage G13 receptor as structural domains of trisaccharides in Salmonella and Escherichia coli core oligosaccharides
Authors: Wollin Ralfh , Bruse Gert W. , Jansson Per‐Erik , Lindberg Alf A. 
Published: May 2005

AbstractThe interaction between phage G13 and different bacterial and synthetic oligosaccharides has been studied using equilibrium dialysis inhibition. The results, and conformational analysis of the oligosaccharides, make us conclude that the phage G13 carbohydrate receptor is a conformational domain involving three sugar residues. The following trisaccharide elements contain in domain: α‐D‐Galp‐(1→3)‐[α‐D‐Galp‐(1→6)]‐α‐D‐Glcp, α‐D‐Manp‐(1→3)‐[α‐D‐Manp‐(1→6)]‐α‐D‐Manp, and α‐D‐Glcp‐(1→3)‐[L‐gly‐α‐D‐man‐Hepp‐(1→7)]‐L‐gly‐α‐D‐man‐Hepp. Thus two structures, either a hexose substituted with α‐D‐glycopyranosyl groups in the 3‐ and 6‐positions, or a heptose substituted with such groups in the 3‐ and 7‐positions are functional G13 binding sites. Such domains are present in several cores of lipopolysaccharides from Salmonella and Escherichia coli species. Some cores, e.g. those from S. typhimurium chemotypes Ra, Rb1 and Rb2, contain two such domains. The identification of two G13 receptor domains within different core saccharides could explain the broad host range this phage.
A monoclonal antibody to a synthetic fragment of rabies virus glycoprotein binds ligands of the nicotinic cholinergic receptor
Authors: Rustici Mauro , Santucci Annalisa , Lozzi Luisa , Petreni Simonetta , Spreafico Adriano , Neri Paolo , Bracci Luisa , Soldani Patrizia 
Published: May 2005

AbstractRabies virus glycoprotein and snake venom curaremimetic neurotoxins share a region of high homology (30–45 for neurotoxins and 190–203 for the glycoprotein) in the regions that are believed to be responsible for binding the nicotinic acetylcholine receptor. Monoclonal antibodies raised to the 190–203 synthetic fragment of rabies virus glycoprotein were immobilized on a high performance affinity chromatography column and were able to bind neurotoxins. Toxins were displaced from the affinity column by elution at acidic pH and by affinity competition with acetylcholine at neutral pH. Furthermore, the affinity column proved to be useful for the purification of cholinergic ligands. Overall, these results indicate that the paratope of our monoclonal antibodies could behave as an ‘internal image’ of the nicotinic cholinergic receptor acetylcholine binding site.