bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass fragmentographic assay for 25‐hydroxyvitamin D in plasma without derivatization: Enhanced sensitivity for metabolites of vitamins D2 and D3 after pre‐column dehydration
Authors: Coldwell Ruth D. , Trafford D. J. H. , Makin H. L. J. 
Published: May 2005

AbstractA mass fragmentographic method for the measurement in plasma of underivatized, dehydrated 25‐hydroxyvitamin D2 and 25‐hydroxyvitamin D3 was developed. Quantitative dehydration of vitamin D metabolites was achieved prior to gas chromatography using a new high‐temperature injection system and a small precolumn packed with aluminium powder in the injection port, followed by mass fragmentography on an inexpensive bench‐top mass spectrometer. Plasma (2 ml) was incubated with hexadeuteriated 25‐hydroxyvitamin D3 prior to acetonitrile extraction and purification using cartridges pre‐packed with microparticulate silica using reversed‐ and normal‐phase solvent systems. After purification, capillary gas chromatography mass spectrometry was carried out following dehydration of the secosteroids on the aluminium power pre‐column at 400°C. High‐intensity dehydrated molecular ions were produced which were used for selected ion monitoring. The assay sensitivity for 25‐hydroxyvitamin D was approximately 1 ng ml−1. The intra‐assay variation was less than 7% and the recovery of added standard was quantitative. It is suggested that this method may be used to provide target values for much needed quality control schemes to monitor assays routinely used in the estimation of 25‐hydroxyvitamin D. The behaviour of a number of other hydroxylated vitamin D metabolites, when injected without derivatization on to a gas chromatographic column, was also investigated.
Quantitative bioanalysis using matrix‐assisted laser desorption/ionization mass spectrometry
Authors: Jespersen S. , Niessen W. M. A. , Tjaden U. R. , van der Greef J 
Published: May 2005

AbstractThe application of matrix‐assisted laser desorption/ionization mass spectrometry (MALDI‐MS) for quantitative analysis was investigated with the use of internal standards. Three peptides/proteins in the mass range 1000–12000 were tested and the effect of various internal standards was evaluated. Horse cytochrome c was used as an internal standard for bovine cytochrome c, melittin for renin and an undecapeptide B analogue was employed as an internal standard for the decapeptide A. A linear response was found between the measured peak height ratio and the applied amount of analyte when an appropriate internal stanard was used. The quantitative abilities of MALDI‐MS were finally applied to the determination of the drug amperozide in plasma. The biological samples were prepared for analysis using liquid–liquid extraction prior to MALDI‐MS. A linear calibration graph was obtained using the 13C4 stable isotopically labelled amperozide as an internal standard.
Identification of the metabolites of MX/2/120 in the guinea‐pig by high‐performance liquid chromatography/thermospray tandem mass spectrometry
Authors: Triolo Antonio , Bonelli Fabio , Agostini Orenzo , Bonacchi Graziano , Toja Emilio 
Published: May 2005

AbstractThe metabolism of MX/2/120, a new xanthine derivative endowed with potent and long‐lasting antibronchospastic activity, was investigated in guinea‐pig urine, plasma and bile after intravenous administration of 12.5 mg kg−1 by high‐performance liquid chromatography/tandem mass spectrometry with thermospray ionization. Following a first series of collisionally activated neutral losses and parent ion scan experiments performed on urine samples, potential quasi‐molecular ions of possible metabolites were identified, which were then analysed by collisionally activated fragment ion scans. A side‐chain carboxylated, a side‐chain hydroxylated and a xanthine‐ring demethylated metabolite, along with the unmodified drug, were identified. In urine, MX/2/120 and its hydroxylated metabolite were also present as glucuronic acid conjugates. In plasma and bile, only the unmodified drug was found. The structures of the identified metabolites were then confirmed by comparison with the authentic compounds prepared by synthesis.
Thin‐layer chromatography/laser desorption of peptides followed by multiphoton ionization time‐of‐flight mass spectrometry
Authors: Krutchinsky A. N. , Dolgin A. I. , Utsal O. G. , Khodorkovski A. M. 
Published: May 2005

AbstractThe location of the separated compounds of GlnTrp/GlyTyr and pentagastrin/gramicidin D peptide model mixtures on silica gel and cellulose thin‐layer chromatography plates has been examined by laser desorption multiphoton ionization time‐of‐flight mass spectrometry. The multiphoton ionization mass spectra of neutrals desorbed by sequential scanning of the thin‐layer chromatography plates versus the infrared laser spot allowed imaging of the distribution profile of the compounds. The method appeared to be promising for the analysis of thin‐layer chromatograms.
A mass‐spectrographic study of the isotopes of argon, potassium, rubidium, zinc and cadmium
Authors: Nier Alfred O. 
Published: May 2005

AbstractA mass spectrograph is described with which a study of the isotopic constitution of argon, potassium, rubidium, zinc and cadmium has been made. A calculation is carried out which indicates that the radioactivity of potassium and rubidium can best be explained by assuming that it is K40 in the case of potassium and Rb87 in the case of rubidium which is undergoing decay.
Utility of nicotinoyl derivatives in structural studies of mono‐ and diacylglycerols by gas chromatography/mass spectrometry. Part 2
Authors: Zöllner P. , Lorbeer E. 
Published: May 2005

AbstractThe positional isomers of mono[(Z)‐9‐octadecenoyl] glycerol, di[(Z)‐12‐octadecadienoyl] glycerol were derivatized with nicotinic acid chloride hydrochloride. The resulting nicotinoyl derivatives were examined by gas chromatography/mass spectrometry. In their electron impact mass spectra, each methylene group and double bond of the alkyl chain is reflected by a fragmentation pattern in the high mass region. This is caused by radical‐induced cleavage of the alkyl chains following random hydrogen abstraction by the pyridine nucleus. An accurate determination of double bond positions in mono‐ and diacylglycerols is possible by characteristic spacings between abundant diagnostic ions in this fragmentation pattern.
Development and application of a gas chromatographic/mass spectrometric/mass spectrometric method for the determination of 5‐methoxyflavone in rat and dog plasma
Authors: Baker Timothy R. , Wehmeyer Kenneth R. , Kelm Gary R. , Tulich Linda J. , Kuhlenbeck Debra L. , Dobrozsi Douglas J. , Penafiel Jorge V. 
Published: May 2005

AbstractA gas chromatographic/mass spectrometric/mass spectrometric method was developed for the determination of 5‐methoxyflavone in plasma. Optimized detection schemes for 5‐methoxyflavone readily allow a limit of quantification of 1 ng ml−1 in rat or dog plasma (1.0 ml sample volume). The complete analysis time (injection to injection) is less than 9 min and allows for rapid automated sample throughput. Additional advantages include a high degree of specifity and good accuracy and precision. This type of rapid tandem mass spectrometric assay has been found to be particularly useful in pharmaceutical discovery, since an assay for one compound can be quickly developed, utilized and then modified to determine analogs of similar structure. Application of this methodology to pilot preclinical pharmacokinetic studies of the drug indicated that it is rapidly absorbed and cleared, with an apparent terminal half‐life of about 15 min in dogs. Bioavailability in the two dogs tested ranged 33 to 72%, but was about 25% in rats.
Use of electrospray ionization and neutral loss liquid chromatography/tandem mass spectrometry in drug metabolism studies
Authors: Jackson P. J. , Brownsill R. D. , Taylor A. R. , Walther B. 
Published: May 2005

AbstractThe application of liquid chromatography/mass spectrometry (LC/MS) and LC/MS/MS with electrospray ionization to drug metabolism studies was investigated using S 9788 and various synthesized metabolic products as model compounds to assess the response characteristics with regard to compound lipophilicity and the influence of biological matrix components. The results obtained demonstrate the versatility of the electrospray ionization technique to analyse compounds of widely varying polarity and the power of MS/MS to identify unequivocally metabolic products. These techniques offer a very rapid screening procedure that can be used to identify metabolic products and thus provide important early metabolic information that can be used in the candidate drug selection programme. These procedures were then applied to an in vivo study sample and, using neutral loss MS/MS, it was possible to detect metabolites of S 9788 directly from a crude biological matrix (bile) without prior extraction or chromatography to confirm positively the identity of five important metabolites of S 9788 in the rat.
Identification of Fenton's reagent‐generated atrazine degradation products by high‐performance liquid chromatography and megaflow electrospray ionization tandem mass spectrometry
Authors: Arnold Scott M. , Talaat Rasmy E. , Hickey William J. , Harris Robin F. 
Published: May 2005

AbstractHigh‐performance liquid chromatography megaflow electrospray tandem mass spectrometry (HPLC/ES‐MS/MS) with an on‐line radioisotope detector was used to identify [2,4,6‐14C] atrazine degradation products generated by treatment with Fenton's reagent (Fe2+ and H2O2). Fenton's reagent produced dealkylated and/or partially oxidized [2,4,6‐14C] atrazine products in preference to dechlorinated products. Seven major products were identified by collision‐induced dissociation spectra: 4‐acetamido‐2‐chloro‐6‐(isopropylamino)‐s‐triazine, 4‐amino‐2‐chloro‐6‐(isopropylamino)‐s‐triazine, 4‐acetamido‐2‐chloro‐6‐(ethylamino)‐s‐triazine, 6‐amino‐2‐chloro‐4‐(ethylamino)‐s‐triazine, 4‐acetamido‐6‐amino‐2‐chloro‐s‐triazine, 2‐chloro‐4,6‐diamino‐s‐triazine and the first report of 4‐acetamido‐2‐hydroxy‐6‐(isopropylamino)‐s‐triazine. HPLC/ES‐MS/MS provided a rapid method for identifying a wide range of atrazine transformation products in aqueous samples and obviated the need for fraction collection, extraction, and chemical derivatization of the more polar atrazine products. Furthermore, because analyte retention times in HPLC/UV and HPLC/ES‐MS/MS were similar, compound identities determined using the latter could be directly assigned to peaks in UV chromatograms.
Mass spectra of 1,3‐dithiaspiranes and 2‐aryl‐1,3‐dithianes
Authors: Shiue Gong‐Yih , Lin Shaw‐Tao , Kuo Yueh‐Hsiung , Chen Zong‐Shiow 
Published: May 2005

AbstractThe mass spectra of 20 1,3‐dithianes were studied. The fragmentation patterns including the loss of 74 u and 107 u and clearage of the substituent at C‐2 depended strongly on the nature of the substituents at that position. 2,2‐Diphenyl‐1,3‐dithiane undergoes an atypical fragmentation in which two hydrogens migrate from the phenyl ring, with the formation of a fluorene skeleton.
High‐sensitivity liquid chromatography–combustion isotope ratio mass spectrometry of fat‐soluble vitamins
Authors: Caimi Richard J. , Brenna J. Thomas 
Published: May 2005

AbstractThe sensitivity of high‐precision liquid chromatography/combustion isotope ratio mass spectrometry (LC/C‐IRMS) was improved by more than two orders of magnitude by modifications which permit optimization of flows. The lower limits for high precision are about 3 μg of analyte on‐column for flow injection and LC modes. Pneumatic aerosol spray coating was implemented and compared with simple dip coating. The signal enhancement for aerosol compared with dip coating is up fourfold at higher levels but drops to less than twofold at lower levels, while the dynamic range is extended at higher levels by fourfold at high sample load levels. LC separations for underivatized tocopherols, retinyl acetate and ergocalciferol are demonstrated with precision and accuracy of about δ13C < 2.5% for replicates. This work demonstrates sensitivity useful for a wide range of LC analyses and extends high‐precision LC/C‐IRMS to the determination of several fat‐soluble vitamins.
Linear free energy correlation in the low‐energy tandem mass spectra of sodiated tripeptides Gly‐Gly‐Xxx
Authors: Morgan Daniel G. , Bursey Maurice M. 
Published: May 2005

AbstractThe backbone cleavages of 14 sodiated tripeptides of the series Gly‐Gly‐Xxx, where Xxx = Gly, Ala, Val, Leu, Ile, Phe, Tyr, Met, Glu, Pro, Trp, Lys, His and Arg, were studied in a hybrid tandem mass spectrometer. A C‐terminal y‐type ion of the form y1 + Na + H was noted in all cases studied. N‐Terminal bn + Na + 17, bn + Na ‐ H and an + Na – H ions, along with internal fragments, were also noted. Because information on sodium affinities of amino acids is limited, the sodiated tripeptides studied were compared not only with the rank ordering of amino acid sodium affinities, but also on the basis of available proton affinities. A linear relationship between log[(y1 + Na + H)/(b2 + Na + 17)] and the proton affinity of the C‐terminal amino acid substituents was found: as the proton affinity of the C‐terminal residue increases, the fraction of y1 ion formation increases. When the C‐terminal substituent was more basic than Trp, the correlation does not hold, probably because the highly basic amino acids, Lys, His, and Arg, are cationized on the side‐chain instead of on the terminal amino group.
Comparison of [5,5,5‐2H3]leucine and [ring‐2H5]phenylalanine tracers for the measurement of human apolipoprotein B100 kinetics
Authors: Maugeais C. , Ouguerram K. , Maugeais P. , Simoneau C. , Gardette J. , Magot T. , Krempf M. 
Published: May 2005

AbstractIncorporation of amino acids labeled with stable isotopes in apoliproproteins is used to estimate kinetic aspects of lipoprotein metabolism. In this study two deuterated tracers, [5,5,5‐2H3]leucine and [ring‐2H5]phenylalanine, were compared. Isolation and acid hydrolysis of apolipoproteins are required for mass spectrometric analysis. When apolipoprotein B100 of very low density liproproteins was prepared with this procedure, a loss of deuterium was observed on deuterated phenylalanine with 10 and 6 M HCl hydrolysis but not with deuterated leucine or when 4 M HCl hydrolysis was used. This study stre sses the effect of acid hydrolysis on [ring‐2H5]phenylalanine. This tracer must be used with caution in studies of specific protein synthesis.
Influence of the matrix on the analysis of small oligoribonucleotides by fast atom bombardment mass spectrometry
Authors: Wolter Marek A. , Engels Joachim W. , Montanarella Luca , Tilio Roberto , Facchetti Sergio 
Published: May 2005

AbstractThe analysis of oligonucleotides by mass spectrometry should give information on both the molecular mass and sequence. Fast atom bombardment mass spectrometry gives both in one step. Until now glycerol, thioglycerol and triethanolamine have been used as matrices for the analysis of oligonucleotides by fast atom bombardment mass spectrometry (FABMS), but there have been no comparative studies for matrix selection for these specific analytes. In this work, the influence of diethanolamine, glycerol, 1‐thioglycerol and triethanolamine on the analysis of unprotected trimer up to heptamer oligoribonucleotides was studied using negative‐ion FABMS on a sector‐type mass spectrometer. Collision‐induced dissociation MS/MS measurements were performed and the fragmentation patterns in MS and MS/MS were compared.
Interconversions of C5H10O+· ions with the oxygen on the first, second and third carbons: Approximately 60 communicating isomers
Authors: McAdoo David J. , Hudson Charles E. 
Published: May 2005

AbstractThe structures of the C4H7O+ and C3H6O+· dissociation products from selected C5H10O+· isomers with the oxygen on the first, second and third carbons were determined. The first product is CH3C(OH)CHCH2+ and the second is CH3C(OH+)CH2⋅ and CH3⋅CHCHOH+ in various proportions. These results demonstrate that ions with the oxygen on the first and third carbons isomerize partially to isomers with the oxygen on the second carbon. This and C5H10O+· isomers expected to be accessible to each other suggest that there are traversable pathways between about 60 C5H10O+· isomers, demonstrating how extensive interconversions of aliphatic radical cations can be.
Profiling 19‐norsteroids. I—tandem mass spectrometric characterization of the heptafluorobutyryl ester and pentafluorobenzyloxime heptafluorobutyryl ester derivatives of 19‐nortestosterone using collisionally activated dissociation
Authors: de Boer D. , Bensink S. N. , Borggreve A. R. , van Ooijen R. D. , Maes R. A. A. 
Published: May 2005

AbstractTandem mass spectrometric methods for the identification of 19‐nortestosterone (estr‐4‐en‐17β‐3‐one) are described and evaluated. The fragmentation reactions of the heptafluorobutyryl (HFB) and pentafluorobenzyloxime heptafluorobutyryl (PFBOHFB) ester derivatives of 19‐nortestosterone in particular were studied for the purpose to select characteristic ions. The HFB ester was analyzed by collisionly activated dissociation (CAD) following electron impact in order to fragment the steroid nucleus. Cleavage of the A‐ring, i.e. the ring containing the keto function, was prominent. The formation of A‐, A/B‐ and D‐ring fragments was also typical for this type of derivative. The PFBOHFB ester was formed to create a derivative, which could capture electrons and be analyzed in the electron‐capture negative chemical ionization (ECNCI) mode. Besides fragmentations originating in the groups coupled to the steroid by derivatization, no prominent steroid nucleus fragmentations were observed by CAD following ECNCI. Accordingly, of both methods only CAD following EI of the HFB derivative of 19‐nortestosterone provided a characteristic MS/MS procedure for the identification of 19‐nortestosterone.
Profiling 19‐norsteroids. II—tandem mass spectrometric characterization of the heptafluorobutyryl ester and pentafluorobenzyloxime heptafluorobutyryl ester derivatives of 19‐norandrosterone using collisionly activated dissociation
Authors: de Boer D. , Bensink S. N. , Borggreve A. R. , van Ooijen R. D. , Maes R. A. A. 
Published: May 2005

AbstractTandem mass spectrometric methods for the identification of 19‐norandrosterone (3α‐hydroxy‐5α‐estran‐17‐one) are described and evaluated. The fragmentation reactions of the heptafluorobutyryl (HFB) and pentafluorobenzyloxime heptafluorobutyryl (PFBOHFB) ester derivatives of 19‐norandrosterone (3α‐hydroxy‐5α‐estran‐17‐one) in particular were studied for the purpose to select characteristic ions. The HFB ester was analyzed by collisionly activated dissociation (CAD) following electron impact in order to fragment the steroid nucleus. The formation of D‐ring fragments, i.e. the ring containing the keto function, was typical for this type of derivative. Cleavages of fragments with an intact D‐ring were also prominent. The PFBOHFB ester was formed to create a derivative, which could capture electrons and be analyzed in the Electron Capture Negative Chemical Ionization (ECNCI) mode. Besides fragmentations originating in the groups coupled to the steroid by derivatization, also characteristic D‐ring fragments were observed by CAD following ECNCI. Accordingly, of both methods evaluated only CAD following EI of the HFB derivative of 19‐norandrosterone provided a characteristic MS/MS procedure for the identification of 19‐norandrosterone under the conditions studied.
Special feature: Perspective. Mass spectrometric peptide and protein charting
Authors: Feistner Gottfried J. , Faull Kym F. , Barofsky Douglas F. , Roepstorff Peter 
Published: May 2005

AbstractSix years after coining the term ‘mass spectrometric (MS) peptide charting’ for the component analysis of peptide mixtures in a whole tissue, body fluid, or an extract thereof, we offer our current perspective of this field. Matrixassisted laser desorption/ionization and electrospray ionization have replaced plasma desorption and fast atom bombardment as ionization methods of choice. At the same time, the upper mass range has been extended to now include most peptides and proteins of interest to research on cell‐cell communication. In addition to qualitative aspects, quantitative applications of MS charting have become important. In combination with new database search algorithms, on‐line liquid chromatography‐tandem mass spectrometry promises greater dividends from MS charting than are achievable with molecular mass matching alone. We discuss what is and is not yet possible, and consider foreseeable means for overcoming current limitations. Our intent is to encourage researchers in the biological and medical sciences to take advantage of this powerful methodology in their various fields of endeavor.
Detection and characterization of native β‐endorphin1–31 in bovine pituitary using electrospray ionization, liquid secondary ion and tandem mass spectrometry
Authors: Yan Lin , Tseng Jih‐Lie , Desiderio Dominic M. 
Published: May 2005

AbstractThe molecular ion of intact β‐endorphinbovine, 1–31 (BE), which was extracted from bovine pituitary, was determined by electrospray ionization mass spectrometry. Liquid secondary ion mass spectrometry determined the molecular masses of three peptides produced by trypsin digestion of BE, and tandem mass spectrometry was used to determine the amino acid sequence of the tryptic peptide BE20–24. These data, in combination, were used to characterize BE in bovine pituitary.
Ammonia chemical ionization mass spectrometry of substituted phenylpropanoids and phenylalkyl phenyl ethers
Authors: van der Hage Erik R. E. , Weeding Tina L. , Boon Jaap J. 
Published: May 2005

AbstractThe ammonia chemical ionization (NH3/CI) spectra of phenylpropanoids and substituted phenylalkyl phenyl ethers containing α‐hydroxy or α‐carbonyl functional groups are discussed. Fragmentation reactions which occur in the temperature range 180–450°C are examined to model pyrolysis mass spectrometric experiments of lignin. Hydroxycinnamyl alcohols and α‐hydroxy phenylalkyl phenyl ethers show abundant [M + H − H2O]+ elimination ions and to a lesser extent [M + NH4 − H2O]+ substitution ions while hydroxycinnamic acids and α‐carbonyl phenylalkyl phenyl ethers show predominantly [M + H]+ and [M + NH4]+ ions. The interpretation of functional group information is facilitated by using trideuterioammonia (ND3) and [15N] ammonia (15NH3) as reagent gases. Labile hydrogens undergo essentially complete exchange upon ND3/CI and the number of hydroxyl functional groups is readily determined by comparison of the [M + NH4]+ and [M − nH + nD + ND4]+ adduct ions. Incomplete HD exchange is observed for enolizable and aromatic protons.