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  • Articles  (19)
  • Chemistry  (19)
  • Capillary isotachophoresis
  • Physics  (19)
  • 1
    Electronic Resource
    Electronic Resource
    Collisional effects on the charge distribution of ions from large molecules, formed by electrospray-ionization mass spectrometry (1988)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 2 (1988), S. 207-210 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290021006
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  • 2
    Electronic Resource
    Electronic Resource
    Bio-affinity characterization mass spectrometry (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 644-650 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A new approach, bio-affinity characterization mass spectrometry (BACMS), aimed at providing a more rapid, sensitive and potentially more flexible alternative to techniques presently employed for the characterization of noncovalent interactions in mixtures, such as would be encountered in combinatorial chemistry, is presented. BACMS avoids some of the difficulties and potential artifacts associated with affinity chromatography since the noncovalent associations occur in solution; thus, BACMS avoids the requirement of solid support media and the development of non-interfering linker species. This paper describes the conceptual basis for the methodology and its potential use in applications which include the screening of high affinity ligands in support of new drug development. BACMS exploits new Fourier-transform ion cyclotron resonance (FTICR) mass spectrometry technologies which, when coupled to electrospray ionization (ESI), allow the investigation of specific noncovalent complexes formed in solution. BACMS utilizes the well-known attributes of FTICR, such as the high resolution mass analysis and (MS)n (n ≥ 2) capabilities; however, it is even more directly a result of recently developed techniques involving quadrupolar excitation, such as selected-ion accumulation. These tools are demonstrated and the results illustrate the extraordinary sensitivity achievable (solution concentrations of 1 × 10-9 M without the use of separations prior to ESI). Thus, the new capabilities demonstrated here, in conjunction with ESI, will be useful for the investigation of very low relative concentration noncovalent association directly from solution, and promote a faster alternative for combinatorial mixture screening and analysis.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090805
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  • 3
    Electronic Resource
    Electronic Resource
    Detection of hydrogen-bonded supramolecular complexes using electrospray ionization from chloroform (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 312-316 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The stoichiometry of a noncovalent, hydrogen-bonded supramolecular complex, hub(M)3·RCA3, was characterized using electrospray ionization from chloroform. The intact (1:3) complex was observed in the negative-ion mode as a Cl--bound species using Ph4PCl as the source of the charge donor. Collisionally and thermally induced dissociation of the (1:3) complex resulted in the simultaneous loss of all the three RCA units, indicating a cooperative binding of RCA units in the (1:3) complex. These results suggest that the attachment of small, organic-soluble ions may be a useful technique for mass spectrometric characterization of neutral supramolecular complexes that are stable or soluble only in non-polar organic solvents.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090410
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  • 4
    Electronic Resource
    Electronic Resource
    Time-base modulation for the correction of cyclotron frequency shifts observed in long-lived transients from fourier-transform ion-cyclotron-resonance mass spectrometry of electrosprayed biopolymers (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 700-703 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The occurrence of small shifts in the cyclotron frequency during the acquisition of very long transients (in excess of 80 s) has been observed to be a limiting factor for ultrahigh-resolution mass measurements of protein ions performed with electrospray-ionization Fourier-transform ion-cyclotron-resonance mass spectrometry. Resolution measurements were restricted to values less than 106 because of the frequency shifts. Measurements of the frequency shifts, performed by sequentially transforming small segments of the transient, allowed the shift to be characterized and fitted to a 4th-order equation. The sampling rate of the acquired transient was then modulated (at a rate equal to the reciprocal of the rate for the frequency shift) to allow ultrahigh resolution, greater than 2 × 106, and improved mass measurement and precision to be achieved for a small protein.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290070803
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  • 5
    Electronic Resource
    Electronic Resource
    Detection of high molecular weight starburst dendrimers by electrospray ionization mass spectometry (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1552-1555 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An entire series of Starburst polyamidoamine (PAMAM) dendrimers consisting of generations 1 through 10 (G1-10) have been studied by positive-ion electrospray ionization mass spectrometry (ESI-MS) using an extended m/z range quadrupole mass spectrometer. Charge-state distributions were detected as high as m/z 12 000 for the generation 10 dendrimer, having a theoretical molecular weight of 1 megadalton and containing approximately 93 maximum positive charges on the molecule. Accurate molecular weight determinations of the smaller generation dendrimers (G1-3, Mr ∼ 1.4kDa to 6.9kDa) were obtained using a commercial triple quadrupole instrument. The unit resolution ESI mass spectra provide information on the number of incomplete reactions which may occur during polymer synthesis. The extent of gas-phase charging observed by ESI-MS on the entire series of macromolecules was found to exhibit a linear relationship to Mr2/3, consistent with theoretical models prediciting a spherical ion structure with maximum charging controlled by Coulombic effects.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091516
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  • 6
    Electronic Resource
    Electronic Resource
    The formation of polymer fibers from the rapid expansion of supercritical fluid solutions (1987)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 27 (1987), S. 1693-1697 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Fibers of organic polymers (polystyrene, cellulose acetate, and polypropylene) were formed by the rapid expansion of supercritical fluid solutions through a small diameter nozzle to ambient temperature and pressure. Solutions were prepared either by dissolving the polymer directly in room temperature pentane, or in an autoclave at elevated temperatures and pressures for less soluble polymers. The fibers were collected on substrates mounted in the expansion jet. The diameters of the fibers formed (typically 1-5 μm) were much smaller than the opening of the nozzle, although fiber diameter was observed to generally increase with nozzle diameter. The aspect ratios of the fibers, produced by this process were on the order of 103 or larger. Optimum conditions for fiber formation occurred at fluid expansion temperatures near the melting point of the polymer, with particle formation mechanisms favored at higher and lower temperatures.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760272208
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  • 7
    Electronic Resource
    Electronic Resource
    Solvent-induced conformational changes of polypeptides probed by electrospray-ionization mass spectrometry (1991)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 5 (1991), S. 101-105 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Electrospray-ionization (ESI) mss spectrometry is used to monitor higher order structural changes of polypeptide induced by alteration of the pH or organic solvent composition in the protein solution environment. A bimodal charge-state disribution is observed in the ESI mass spectrometry of ubiquitin (relative molecualr mass 8565) in solution containing small amounts (〈20%) of organic solvents. The distribution of peaks at high m/z (low-charge state) is found to represent the protein in its native, globular state; the higher-charge-state distribution is characteristic for a more extended conformation. Addition of methanol denaturant in excess of 40% v/v is needed to eliminate the low-charge-state distribution completely. Lesser amounts of acetonitrile, acetone, or isopropanol (∼20%) are reqiored to denature the ubiquitin protein. Other proteins showing conformational efects in their ESI mass spectra are also illustrated. While the ESI spectra are related to solution phase structure, ESI-tandem mass spectrometry of multiply charged molecular ions of different conformation is suggested as a probe of gas-phase protein three-dimensional structure.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290050303
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  • 8
    Electronic Resource
    Electronic Resource
    Selected-ion accumulation from an external electrospray ionization source with a fourier-transform ion cyclotron resonance mass spectrometer (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 914-919 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The coupling of an electrospray ionization (ESI) source to a Fourier-transform ion cyclotron resonance (FTICR) mass spectrometer provides a facility for the high resolution, accurate mass analysis of large biopolymers. Typically the m/z range of the electrosprayed ions injected and trapped in the FTICR cell is between m/z 500 and 2500 (but can vary considerably with solution conditions). Recent reports on quadrupole excitation have demonstrated the ability to cool the magnetron motion of ions trapped in the FTICR mass spectrometer cell by converting this motion to cyclotron motion which, under appropriate pressure conditions, damps readily to the center of the cell. The use of a broadband waveform (swept frequency or stored waveform inverse Fourier-transform) for the quadrupole cooling pulse was shown to provide cooling of a wide range of m/z ions, while implementation of a single frequency demonstrated a much narrower m/z response. This report demonstrates the successful combination of single-frequency quadrupole cooling with external injection of electrosprayed ions into an FTICR mass spectrometer for m/z selected-ion accumulation. This capability is particularly significant with electrospray ionization since it allows ions of only one charge state to be accumulated in the cell, and greatly increases the potential dynamic range of ESI-FTICR.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290071012
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  • 9
    Electronic Resource
    Electronic Resource
    Small volume and low flow-rate electrospray lonization mass spectrometry of aqueous samples (1993)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 7 (1993), S. 1017-1021 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: A new electrospray ionization source (emitter) has been developed which allows the effective utilization of very small sample volumes at much lower flow rates than previously demonstrated. A small diameter etcched-tip capillary has been incorporated into a pressure-infusion electrospray ionization source. The ability to electro-spray aqueous solutions without the use of an ancillary sheath flow is demonstrated with several biopolymers. High signal intensities and stable signals are observed for this source in a comparison with a standard methanol-sheath source.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290071111
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  • 10
    Electronic Resource
    Electronic Resource
    Internal energy effects in the collision-induced dissociation of large biopolymer molecular ions produced by electrospray ionization tandem mass spectrometry of cytochrome c (1990)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 4 (1990), S. 54-57 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The effects of internal energy upon metastable and collision-induced dissociation (CID) processes observed in the tandem mass spectrometry of multiply protonated molecules of horse-heart cytochrome c (Mr 12360) are described. The internal energy of the multiply protonated (15H+) molecules (at m/z 825) formed by electrospray ionization (ESI) was manipulated using electric fields in the atmospheric pressure/vacuum interface region. Highly efficient CID is obtained for molecular ions collisionally activated in the ESI interface. The dissociation efficiency at 3.8 eV to 5.8 eV (center of mass) collision energies for internally “hot” molecular ions under multiple collision conditions in a triple quadrupole mass spectrometer is shown to be much greater than for “cold” ions. The CID spectra show dramatic effects due to internal energy, with charge stripping dominating for cold ions (where CID efficiency is very low) and extensive fragmentation observed for hot ions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290040205
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