Gas-phase conformations of cationized poly(styrene) oligomers

Jennifer Gidden, Michael T. Bowers, Anthony T. Jackson, James Scrivens

    Research output: Contribution to journalReview article

    59 Citations (Scopus)

    Abstract

    The gas-phase conformations of poly(styrene) oligomers cationized by Li+, Na+, Cu+, and Ag+ (M+PSn) were examined using ion mobility experiments and molecular mechanics/dynamics calculations. M+PSn ions were formed by MALDI and their ion-He collision cross-sections were measured by ion mobility methods. The experimental collision cross-sections of each M+PS n-mer were similar for all four metal cations and increased linearly with n. Molecular modeling of selected M+PS oligomers cationized by Li+ and Na+ yielded quasi-linear structures with the metal cation sandwiched between two phenyl groups. The relative energies of the structures were ∼2-3 kcal/mol more stable when the metal cation was sandwiched near the middle of the oligomer chain than when it was near the ends of the oligomer. The cross-sections of these theoretical structures agree well with the experimental values with deviations typically around 1-2%. The calculations also show that the metal cation tends to align the phenyl groups on the same side of the -CH2-CH- backbone. Calculations on neutral poly(styrene), on the other hand, showed structures in which the phenyl groups were more randomly positioned about the oligomer backbone. The conformations and metal-oligomer binding energies of M+PS are also used to help explain CID product distributions and fragmentation mechanisms of cationized PS oligomers.

    Original languageEnglish
    Pages (from-to)499-505
    Number of pages7
    JournalJournal of the American Society for Mass Spectrometry
    Volume13
    Issue number5
    DOIs
    Publication statusPublished - 1 May 2002

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