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High-resolution ultra-high mass spectrometry: Increasing the m/z range of protein analysis

Authors


  • Colour Online: See the article online to view Fig. 4 in colour.

Correspondence: Dr. Peter T. A. Reilly, Department of Chemistry, Washington State University, Pullman, WA 99164, USA.

E-mail: pete.reilly@wsu.edu

Fax: +1-519-335-5334

Abstract

The proof of principle for high-resolution TOF mass analysis spanning the entire range of intact singly charged proteins has recently been demonstrated. The centers of the isotope distributions of individual proteins in a complex distribution can be defined to within 0.5 Da or better up to 200 kDa with internal calibration. This achievement will have an enormous effect on the process of routine protein analysis over the next few years as the technology mainstreams. The greatest obstacle to high-resolution in the ultra-high mass range (m/z > 20 000) is the expansion-induced kinetic energy (KE) and its spread. The solution to this problem is to trap the ions in a buffer gas so that the motion of the ions can be completely defined by the applied fields. If this can accomplished without mass dependence, then any ion, regardless of size, can be mass analyzed with high resolution. This article discusses the methodology that we used to capture atmosphere sampled singly charged proteins in vacuum at a point just before they enter the mass analyzer to completely eliminate the expansion-induced KE. We then used digitally created quadrupole waveforms to inject the ions into the mass analyzer in a well-collimated plug with a controlled amount of KE. Trapping the ions to remove the expansion-induced KE and then electrodynamically manipulating the ions are the key steps to high-resolution mass analysis at any value of m/z. The impact of this technology will be discussed.

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