Pui Shuen Wong

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A significant trend in analytical chemistry today is away from the use of laboratory methods and instrumentation toward online, in situ methods. The latter methods provide diagnostic information that can help solve critical problems faster, less expensively, and more reliably than current analytical methods. Mass spectrometry (MS) already plays a prominent(More)
Cluster ions, Py1SiCl 3 (+) Py2 and Py1SiCl(+)Py2, where Py1 and Py2 represent substituted pyridines, formed upon reactive collisions of mass-selected SiCl 3 (+) or SiCl(+) cations with a mixture of pyridines, are shown to have loosely bound structures by multiple stage mass spectrometry experiments in a pentaquadrupole mass spectrometer. The fragment ion(More)
Electron capture dissociation (ECD) of model peptides adducted with first row divalent transition metal ions, including Mn(2+), Fe(2+), Co(2+), Ni(2+), Cu(2+), and Zn(2+), were investigated. Model peptides with general sequence of ZGGGXGGGZ were used as probes to unveil the ECD mechanism of metalated peptides, where X is either V or W; and Z is either R or(More)
Peptides adducted with different divalent Group IIB metal ions (Zn(2+), Cd(2+), and Hg(2+)) were found to give very different ECD mass spectra. ECD of Zn(2+) adducted peptides gave series of c-/z-type fragment ions with and without metal ions. ECD of Cd(2+) and Hg(2+) adducted model peptides gave mostly a-type fragment ions with M(+•) and fragment ions(More)
Molecular motion of metal-free and metal-substituted cytochrome c derivatives was examined using the anisotropy of emissions from the singlet and the triplet states. The anisotropy of fluorescence provides a means to study the motion of cytochrome c in the nanosecond time scale, since the fluorescence lifetime of metal-free cytochrome c is around 10 ns. We(More)
Reactions of laser-desorbed Na(+), K(+), Rb(+), and Cs(+) with thermally vaporized valinomycin generate metal-ligand complexes in a Fourier transform ion cyclotron resonance trapping cell, proving that complexes can form via gas-phase ion-molecule reactions. Although desorption of intact pre-formed complexes cannot be ruled out, this route appears minor.(More)
Ionization energies of organic compounds can be determined by the kinetic method by dissociation of radical cations of van der Waals complexes. The ionized dimeric complexes of benzene and substituted benzenes, generated in the ion source of a multiquadrupole instrument by gentle charge exchange chemical ionization using carbon disulfide as reagent gas,(More)
Substituted 1,2-diphenylethanes undergo competitive dissociations upon electron ionization (EI) to generate substituted benzyl cation and benzyl radical pairs. Application of the kinetic method to the previous reported EI mass spectra of these covalently bound precursor ions (data are taken from McLafferty et al. J. Am. Chem. Soc. 1970, 92, 6867)) is used(More)
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