bluuebunny/crossref_metadata_2025_split huggingface dataset:
Matrix‐assisted laser desorption ionization for rapid determination of the sequences of biologically active peptides isolated from support‐bound combinatorial peptide libraries
Authors: Scott Youngquist R. , Fuentes Gary R. , Lacey Martin P. , Keough Thomas , Baillie Thomas A. 
Published: May 2005

AbstractA termination synthesis approach has been developed to encode each resin bead in support‐bound combinatorial peptide libraries with the information needed to establish the sequence of the full‐length products also contained on the beads. Matrix‐assisted laser desorption ionization mass spectrometry was then used to rapidly read the appropriate sequences. In addition to rapid peptide sequencing, the technique allows direct assessment of the quality of the synthetic library, since deletion peptides, side‐reaction products and incomplete‐deprotection products are readily observed. An anti‐gp120 monoclonal antibody was screened against a hexapeptide library, and eight active peptides were isolated. Six of the eight peptides were shown to possess the exact recognition sequence for the antibody.
Analysis of fumonisin B1 by negative‐ion thermospray mass spectrometry
Authors: Thakur Rohan A. , Scott Smith J. 
Published: May 2005

AbstractThermospray mass spectrometry was used to analyze fumonisin B1 (FB1) from two corn samples that were known to contain fumonisins, and from a FB1‐spiked meat sample. The mass spectrometer was operated in the negative‐ion discharge‐on, filament‐off, mode with the fragmentor set at 200 V. Selected‐ion monitoring (SIM) was used for quantitative analysis. The mobile phase was CH3CN (containing 1% CICH2CN, v/v)+0.1M ammonium acetate, pH 3.65 (65:35, v/v). Quantitative analysis was done by integrating the peak areas traced by ion currents of 5 selected ions in SIM, and by the method of standard additions. Responses to the selected ions were linear within the range of 2‐200 ng. Fumonisins were easily identified in the corn and muscle tissue matrices without any apparent matrix interferences and were detectable down to 0.1 μ/mL (2 ng injected).
Identification of phosphorylated peptides from complex mixtures using negative‐ion orifice‐potential stepping and capillary liquid chromatography/electrospray ionization mass spectrometry
Authors: Ding Jianmei , Burkhart William , Kassel Daniel B. 
Published: May 2005

AbstractA rapid method for identifying and characterizing sites of phosphorylation of peptides and proteins is described. High‐performance capillary liquid chromatography (HPLC) coupled with electrospray ionization mass spectrometry (ESI‐MS) is used to distinguish non‐phosphorylated and phosphorylated peptides originating from mixtures as complex as enzyme digests. The method relies on the ability to produce a fragment ion characteristic and unique to phosphopeptides (m/z 79, PO3−) by stepping the orifice potential of the mass spectrometer as a function of mass. At low m/z values, a high orifice potential is applied to induce extensive fragmentation of the peptide, leading to the formation of the m/z 79 phosphate‐derived ion. This method is analogous to that described by Carr et al. for the identification of glycopeptides from enzymatic digestion of glycoproteins (S.A. Carr, M. J. Huddleston, M. F. Bean, Protein Science 2, 183 (1993)). The method was first evaluated and validated for a mixture of non‐, mono‐ and di‐phosphorylated synthetic peptides. Both mono‐ and di‐phophorylated peptides were found to generate fragment ions characteristic of PO3− whereas the non‐phosphorylated peptide did not. Application of the method was extended to identifying phosphopeptides generated from an endoprotease Lys‐C digestion of β‐casein. Both the expected mono‐ and tetra‐phosphorylated Lys‐C peptides were observed and identified rapidly in the LC/SEI‐MS analysis. The procedure was used additionally to identify the site(s) of phosphorylation of the cytosolic non‐receptor tyrosine kinase, pp60c‐src.
Capillary column supercritical fluid chromatography/mass spectrometry of polycyclic aromatic compounds using atmospheric pressure chemical ionization
Authors: Thomas Darren , Greig Sim P. , Benoit Frank M. 
Published: May 2005

AbstractCapillary column supercritical fluid chromatography (SCF) was combined with atmospheric pressure chemical ionization (APCI) mass spectrometry through a heated pneumatic‐nebulizer interface, originally developed for liquid chromatography/mass spectrometry (LC/MS), and subsequently modified for use with supercritical fluid chromatography/mass spectrometry (SFC/MS). A high pressure syringe pump was used to pass SFC‐grade carbon dioxide, used as the mobile phase, through a capillary SFC column which was contained in an oven, maintained at 100°C. The eluent passed through the heated pneumatic‐nebulizer interface into the ionization region of the mass spectrometer with the aid of the flow of nebulizing gas. The system was optimized using benz[a]anthracene, and then applied to analyze a standard mixture of polycyclic aromatic compounds (PACs) as well as complex mixtures of PACs obtained by the fractionation of a pond sediment contaminated by coke‐oven residues. A detection limit of 40 pg was established for chrysene.
The evaluation of several electrospray systems and their use in non‐covalent bonding studies
Authors: Haskins Neville J. , Ashcroft Alison E. , Phillips Andrew , Harrison Mark 
Published: May 2005

AbstractA number of different designs of electrospray sources have been used to study the non‐covalent interaction between ribonuclease A and cytidylic acids. Signal differences were observed between the various types of source giving rise to very different spectra. However, in all cases, information was obtained relating to the putative complex.
Electrospray tandem mass spectrometry in the diagnosis of organic acidemias
Authors: Rashed M. S. , Ozand P. T. , Harrison M. E. , Watkins P. J. F. , Evans S. , Baillie Thomas A. 
Published: May 2005

AbstractA novel procedure based on electrospray tandem mass spectrometry (ESI‐MS/MS) has been used in the diagnosis of organic acidemias. The method is based on the determination of acylcarnitine profiles from blood spots collected on Guthrie cards. The acylcarnitines are extracted with methanol, derivatized to their butyl esters and analyzed by ESI‐MS/MS. Precursor‐ion scanning of the common fragment at m/z 85 of the butyl esters yields highly diagnostic acylcarnitine profiles. Analysis time is one minute per sample and is fully automated. Examples are given of normal profiles, of profiles from two patients with fatty acid oxidation defects, and of a case of propionic acidemia. The technique is simple, rapid and specific, and shows potential for routine application in neonatal screening of organic acidemias.
Quantitative determination of β(1–2) cyclic glucans by matrix‐assisted laser desorption mass spectrometry
Authors: Garozzo Domenico , Spina Emanuela , Sturiale Luisa , Montaudo Giorgio , Rizzo Roberto , Daolio S. 
Published: May 2005

AbstractThe use of matrix‐assisted laser desorption/ionization mass spectrometry for the determination of the molecular weight distribution of cyclic β (1–2) glucans is reported here. Quantitative response is demonstrated by the use of different instruments and by comparison with high‐performance liquid chromatography/refractive index detection analysis.
Reactions of Sc+, Ti+, V+, Fe+, Co+ and Ni+ with 1‐fluoronaphthalene in the gas phase. Metal‐catalyzed oligomer formation and observation of unusual ring fragmentation
Authors: Bjarnason Asgeir , Freiser Ben S. 
Published: May 2005

AbstractPoly(naphthalyne) is of interest, in particular, due to its intrinsic electrical conductivity. Reported here are the initial steps in the metal‐catalyzed polymerization of naphthalene as observed in the gas‐phase reactions of Sc+, Ti+, V+, Fe+, Co+, and Ni+ with 1‐fluoronaphthalene studied in a Fourier‐transform mass spectrometer. Sc+, Ti+, V+, and Fe+ were found to dehydrofluorinate in a sequential fashion up to three neutral fluoronaphthalene molecules to form ions of the form MC10H, MC20H and MC30H, where M represents the metal. Sc+ showed unusual reactivity by also being able to eliminate C2H2 from fluoronaphthalene, and Ti+ was found to eliminate a hydrogen atom to form TiC10H6F+. Second‐ and higher‐order reactions were studied and several ionic products from primary and secondary reactions were investigated by collision‐induced dissociation. Formation of unmetallated ions was also observed. For example, C20H was determined to arise from MFC20H, for M = Ti, V, while for iron it was formed directly from FeC10H in its reaction with the neutral fluoronaphthalene. This is in contrast with the behavior expected from an earlier study of fluorobenzene, where it was observed that (C6H4) species arose from M(C6H4) species.
Deprotonation reactions of multiply protonated ubiquitin ions
Authors: Cassady Carolyn J. , Wronka John , Kruppa Gary H. , Laukien Frank H. , Hettich Robert 
Published: May 2005

AbstractThe gas‐phase deprotonation reactions of multiply protonated ubiquitin ions have been studied in a Fourier‐transform ion cyclotron resonance mass spectrometer. Electrospray ionization was used to generate ubiquitin ions with attachment of 7–13 protons. Rate constants were measured for the reactions of these protein ions with four amines: n‐propylamine, di‐n‐propylamine, tri‐n‐propylamine, and N,N,N′,N′‐tetramethyl‐1,4‐diaminobutane. The gas‐phase basicities of the amines ranged from 210.1 kcal/mol to 232.6 kcal/mol. The rate constants were found to increase as the charge state of the ion increased and as the basicity of the amine increased. Several reactions proceed at near the collision rate and have rate constants in excess of 10−8 cm3 molecule−1 s−1. With the more basic reactants, multiple protons could be stripped sequentially from ubiquitin ions at roughly equivalent rates, suggsting that these protons are attached to sites with similar basicities. In general, deprotonation occurs if the gas‐phase basicity of the amine is within 10 kcal/mol of the intrinsic gas‐phase basicity of the amino acid residue being deprotonated. For [M+nH]n + , n = 4–6, nonlinear pseudo‐first‐order kinetic behavior indicated the presence of multiple ion structures. Kinetic, structural and thermodynamic aspects of these reactions are discussed.
Fragmentation of gold clusters stored in a penning trap
Authors: Becker St. , Dietrich G. , Hasse H.‐U. , Klisch N. , Kluge H.‐J. , Kreisle D. , Krückeberg St. , Lindinger M. , Lützenkirchen K. , Schweikhard L. , Weidele H. , Ziegler J. , Nibbering N. M. M. 
Published: May 2005

AbstractThe collision‐induced dissociation of positively charged gold clusters (2–23 atoms) stored in a Penning trap has been studied. After collisions with rare gases, excited clusters predominantly decay by emission of one or two atoms. The loss of two atoms occurs most probably through the emission of a dimer rather than by a sequential evaporation. The minimum kinetic energies of clusters required to induce dissociation exhibit a pronounced odd–even effect. Clusters with an even number of delocalized electrons are more stable than those with an odd number.
Formation of multiply charged ions from large molecules using massive‐cluster impact
Authors: Mahoney John F. , Shannon Cornett D. , Lee Terry D. , Barofsky Douglas F. 
Published: May 2005

AbstractMassive‐cluster impact is demonstrated to be an effective ionization technique for the mass analysis of proteins as large as 17 kDa. The design of the cluster source permits coupling to both magnetic‐sector and quadrupole mass spectrometers. Mass spectra are characterized by the almost total absence of chemical background and a predominance of multiply charged ions formed from 100% glycerol matrix. The number of charge states produced by the technique is observed to range from +3 to +9 for chicken egg lysozyme (14 310 Da). The lower m/z values provided by higher charge states increase the effective mass range of analyses performed with conventional ionization by fast‐atom bombardment or liquid secondary ion mass spectrometry.
The complexation and chiral selectivity of 2‐hydroxypropyl‐β‐cyclodextrin with guest molecules as studied by electrospray mass spectrometry
Authors: Haskins Neville J. , Saunders Martin R. , Camilleri Patrick , Games David E. 
Published: May 2005

AbstractElectrospray mass spectrometry has been used to study the complexation of ‘guest’ molecules with a mixture of hydroxypropyl‐substituted β‐cyclodextrin derivatives. In all cases studied, the predominant derivative was shown to contain a maximum of seven hydroxypropyl groups, most probably related to alkylation of each of the seven glucose units of the parent β‐cyclodextrin. Chiral selectivity was not observed for D‐ and L‐phenylalanine methyl esters. In contrast D‐propranolol and L‐tryptophan methyl ester formed stronger complexes than the corresponding L‐ and D‐enantiomers, respectively. Molecular modelling studies were also carried out, in an attempt to identify the factors that can play a part in determining the mechanism of the observed non‐covalent interactions.
High temperature mass spectrometric study of 3Al2O3 · 2SiO2
Authors: Schornikov S. I. , Stolyarova V. L. , Shultz M. M. 
Published: May 2005

AbstractThe high‐temperature Knudsen effusion method was used to study the vaporization processes and thermodynamic properties of mullite from 1833 K to 2033 K. Data on the activities of Al2O3 and SiO2 and on the entropy, enthalpy and Gibbs energy of formation of mullite were obtained. It was shown that the atomization energy of the AlSiO gaseous molecule (1062±25 kJ/mol) is close to the values that have been obtained earlier.
Chromatographic and mass spectrometric methods for the identification of phosphorylation sites in phosphoproteins
Authors: Hunter Ann P. , Games David E. 
Published: May 2005

AbstractThe phosphorylation sites in a model phosphoprotein, αsl‐casein from bovine milk, have been identified by tryptic peptide mapping (Gibson and Cohen, Methods Enzymol. vol. 193, p. 480 (1990)) employing reversed‐phase high performance liquid chromatography (RPHPLC)/electrospray ionization mass spectrometry (ES‐MS); by infusion tandem mass spectrometry (MS/MS) and LC/MS/MS in neutral loss mode of tryptic digests of αsl‐casein, in which the characteristic neutral loss of phosphoric acid by phosphopeptides under collision‐induced dissociation (CID) conditions is exploited to highlight phosphopeptides in a tryptic digest (Covey et al., in Methods in Protein Sequence Analysis, Jörnvall et al. (Eds), Birkhäuser Verlag, Basel 1991), and by a novel method, termed LC/CID‐MS, in which phosphopeptides are located in mixtures of peptides by the generation and detection of phosphate‐specific fragment ions during LC/ES‐MS (Huddleston et al., J. Am. Soc. Mass Spectrom. vol. 4, p. 710 (1993)). An appraisal of the efficiency, sensitivity and practicality of each of these methods in the identification of phosphorylation sites in post‐translationally modified proteins is given.
Determination of fumonisins using on‐line liquid chromatography coupled to electrospray mass spectrometry
Authors: Doerge Daniel R. , Howard Paul C. , Bajic Steve , Preece Steve , Games D. E. 
Published: May 2005

AbstractFumonisin (FB) mycotoxins are produced by Fusarium monoliforme, which grows primarily on yellow corn. Ingestion of FB1‐contaminated food causes leukoencephalomalacia in horses, pulmonary edema in pigs, and is suspected in the etiology of human esophageal cancer. Chromatographic separation and detection of underivatized fumonisins has been hampered because these compounds are nonvolatile, thermally labile, and devoid of chromophoric functional groups. We report here a simple liquid chromatography/mass spectrometry method employing chromatographic separation on a polymer‐based column coupled with sensitive detection using positive‐ion electrospray mass spectrometry for the quantification of fumonisins B1, B2 and B3 in extracts of commercial corn meal.
Mass determination of human immunoglobulin IgM using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry
Authors: Nelson Randall W. , Dogruel David , Williams Peter , Beavis Ronald 
Published: May 2005

AbstractMonoclonal human immunoglobulin IgM has been analyzed using matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry. Using a matrix of sinapinic acid with a laser wavelength of 355 nm, positive ions with 2 to 6 charges were observed in the mass spectra. Two major molecular species were present. The molecular weights estimated from the multiply‐charged signals were found to decrease systematically with decrease in the charge state of the ion. This effect was determined to stem from the non‐linear influence of the initial kinetic energy of desorption on the final kinetic energy of the multiply‐charged species. A method of successive approximations, with the molecular weights and desorption velocities of the analytes as variables, was used to correct for these non‐linearities. Mean molecular weights for the two IgM species were found to be 939 000 ± 2000 and 982 000 ± 2000 Da. An initial desorption velocity of 565 ± 10 ms/s was determined for both.
Rearrangements of doubly charged acylium ions from lysyl and ornithyl peptides
Authors: Tang Xue‐Jun , Boyd Robert K. 
Published: May 2005

AbstractThe study of large‐scale rearrangements of [b′]2+ ions produced by electrospray ionization of Substance P (Tang et al., Anal. Chem. Vol. 65, p. 2824 (1993)) has been extended to 18 other peptides containing either a lysine or ornithine residue remote from the C‐terminus. Evidence for wholesale transfer of one or more residues, from the C‐terminus of the [b′]2+ precursor to the ω‐amino group of the Lys (or Orn) residue, was observed for 12 of the 18 peptides studied. Unfortunately, no rigorous predictive rules, relating features of the peptide sequence to the propensity to undergo such rearrangements, could be discerned although a significant correlation with presence of a proline residue dose to the lysine or ornithine on the C‐terminal side was apparent. The resulting mass‐shifts can complicate derivation of peptide sequences from fragment‐ion spectra of [M+2H]2+ peptide ions, for example, since the cyclized [b′]2+ ions responsible for the rearrangements are readily formed as intermediate species in the fragmentation mechanisms.
Formation of pentavalent silicon anions, (CH3O)2Si(OEt) and CH3OSiH(OEt), in the gas phase
Authors: Murthy Vemisetty S. , Miller Jack M. 
Published: May 2005

AbstractWe describe the formation of pentavalent silicon anions, (CH3O)2Si(OEt) and CH3OSiH(OEt), by a ligand exchange and a hydride reaction in the presence of argon buffer in the gas phase. A simple elimination is followed by double and triple cyclic elimination mechanisms, during the collision‐induced dissociation of CH3OSiH(OEt).
Investigation of ruthenium (II) and iron (II) tris‐bipyridyl complexes by means of 10–30 keV Cs+ ion bombardment and collision‐induced dissociation
Authors: Bignozzi Carlo A. , Bortolini Olga , Curcuruto Ornella , Hamdan Mahmoud 
Published: May 2005

Abstract[Ru(bpy)3(X)2] and [Fe(bpy)3(X)2] complex salts (bpy=2,2′bipyridine; X = ClO, PF, Cl−) were investigated by means of Cs+ fast‐ion bombardment and mass‐selected collision‐induced dissociation (CID). A number of dissociation channels which can be attributed to the loss of intact counterions, bpy neutral ligands and to the insertion of formal O, fluoride or chloride from the counterions ClO, PF, Cl− are evident in both the fast‐ion bombardment and CID spectra. Formation of doubly charged intact cations is also observed for all the compounds investigated. The relative intensities of the major desorbed ions are monitored as a function of the Cs+ kinetic energy in the range 10–30 keV.
Laser desorption/gas‐phase ionization of the amino acid tryptophan
Authors: Reilly Peter T. A. , Reilly James P. 
Published: May 2005

AbstractA solution of tryptophan, rhodamine B and glycerol is irradiated in the source region of a time‐of‐flight mass spectrometer by visible light from a pulsed laser. Tryptophan and rhodamine B are desorbed and subsequently ionized by a second pulse of ultraviolet light. The observed mass spectra and dependence of ion yields on time delay between light pulses provide information about the laser desorption process.
Exact fields in multi‐electrode ion optics
Authors: Reuben Andreas J. , Radchik Alex V. , Smith Geoffrey B. , Vagov Alex V. 
Published: May 2005

AbstractThe exact determination of electrostatic potential is vital in specifying the resolution in ion‐beam focusing devices such as quadrupole mass spectrometers (QMS). Current numerical routines are marked by poor convergence on boundaries and become unwieldy when the number of electrodes, 2n, is greater than four, or when the structure is modified. Using a conformal transformation we have succeeded in finding the exact electrostatic potential distribution everywhere within a QMS which contains four cylindrical electrodes. All the coefficients in the multipole expansion of the potential are readily calculated. The boundary value problem is solved by matching coefficients on the electrode surface, which is a circle embedded in the transformed coordinate frame. We have proven that for every allowed position of the electrode centre, R, there exists a corresponding electrode radius, r, for which the dodecapole term in the potential expansion vanishes. Our analytically obtained relationship between the above‐mentioned parameters differs slightly from that in current use. As these parameters are based on an exact solution, their practical use in mass determination may be considerable.
Characterization of cyclodepsipeptide‐glutathionyl conjugates by negative‐ion fast‐atom bombardment linked‐scan mass spectrometry
Authors: Loutelier C. , Marcual A. , Cherton J.‐C. , Lange C. 
Published: May 2005

AbstractA cyclodepsipeptide‐glutathionyl conjugate has been analysed for the first time using negative‐ion fast‐atom bombardment linked‐scan mass spectroscopy. Fragment anions produced by collision‐induced dissociation are discussed.
Sequential product‐ion spectra (MS3) with array detection and reaction‐intermediate scanning of a cyclopeptide on a five‐sector mass spectrometer
Authors: Lange C. , Loutelier C. , Bordoli R. S. 
Published: May 2005

AbstractA new strategy, based on sequential product‐ion spectra (MS2 and MS3) and reaction‐intermediate scanning (MS3), provides a rapid and unambiguous sequence determination of E‐destruxin, a cyclodepsipeptidic toxin from Metarrhizium anisopliae fungus.
Self‐calibrating property of matrix‐assisted laser desorption/ionization time‐of‐flight spectra of polymeric materials
Authors: Montaudo Giorgio , Montaudo Maurizio S. , Puglisi Concetto , Samperi Filippo , Daolio S. 
Published: May 2005

AbstractA calibration procedure is introduced, which allows one to obtain absolute mass values in matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) spectra of polymeric materials, thus avoiding ambiguous mass assignments. The method consists in combining the observed times of flight in a function denoted as ‘modified sum of squares’ (SS2) and in finding the point of minimum for SS2. The procedure takes advantage of the finding that SS2 possesses an extremum property, i.e. it takes its minimum at θ, the mass of the first oligomer appearing in the MALDI‐TOF spectrum. The method was tested by recording the MALDI‐TOF spectrum of an aminolyzed Nylon 6 and of a glycolized poly(butyleneadipate) (PBA) sample. Nylon 6 was found to be made of a series of oligomers bearing diaminohexamethylene (DAHM) terminal groups. PBA is made of a series of oligomers with butyleneglycol end‐groups. The intense peaks seen in the mass spectra are due to sodium‐cationized ions, whereas the less‐intense peaks are due to potassium‐cationized ions. The function SS2 was built for the two samples and a point of minimum was found at the point θ = 817.6 for Nylon 6 and at the point θ = 713.6 for PBA. This finding allowed the interpretation of the mass spectra.