Matrix-free detection of intact ions from proteins in argon-cluster secondary ion mass spectrometry

Authors

  • Kozo Mochiji,

    Corresponding author
    1. Department of Mechanical and Systems Engineering, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
    • Department of Mechanical and Systems Engineering, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan.
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  • Michihiro Hashinokuchi,

    1. Department of Mechanical and Systems Engineering, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
    Current affiliation:
    1. Renovation Center of Instruments for Science Education and Technology, Osaka University, Toyonaka, Osaka 563-0043, Japan.
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  • Kousuke Moritani,

    1. Department of Mechanical and Systems Engineering, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
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  • Noriaki Toyoda

    1. Department of Mechanical and Systems Engineering, Graduate School of Engineering, University of Hyogo, 2167 Shosha, Himeji, Hyogo 671-2280, Japan
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Abstract

In the secondary ion mass spectrometry (SIMS) of organic substances, the molecular weight of the intact ions currently detectable is at best only as high as 1000 Da, which for all practical purposes prevents the technique from being applied to biomaterials of higher mass. We have developed SIMS instrumentation in which the primary ions were argon cluster ions having a kinetic energy per atom, controlled down to 1 eV. On applying this instrumentation to several peptides and proteins, the signal intensity of fragment ions was decreased by a factor of 102 when the kinetic energy per atom was decreased below 5 eV; moreover, intact ions of insulin (molecular weight (MW): 5808) and cytochrome C (MW: 12 327) were detected without using any matrix. These results indicate that fragmentation can be substantially suppressed without sacrificing the sputter yield of intact ions when the kinetic energy per atom is decreased to the level of the target's dissociation energy. This principle is fully applicable to other biomolecules, and it can thus be expected to contribute to applications of SIMS to biomaterials in the future. Copyright © 2009 John Wiley & Sons, Ltd.

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