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Updated: May 6, 2026

Analyzing Large Protein Complexes by Structural Mass Spectrometry
Published on: June 19, 2010
Dissociation of tetrameric ions of noncovalent streptavidin complexes formed by electrospray ionization
B L Schwartz1, J E Bruce, G A Anderson
1Chemical Methods and Separations Group, Chemical Sciences Department, Pacific Northwest Laboratory, P. O. Box 999, Mail Stop P8-19, 99352, Richland, WA.
Abstract:
The noncovalent tetrameric association of the protein streptavidin formed by electrospray ionization (ESI) mass spectrometry has been observed intact and dissociated in the gas phase. An extended mass-to-charge ratio range quadrupole mass spectrometer was employed to examine the effects of harsher conditions in the ESI atmosphere-vacuum interface region on the streptavidin tetramer. Thermally induced dissociation caused the mass spectra to exhibit a series of complementary monomer and trimer ions that correspond to decomposition of the tetrameric species. Similar results were obtained with tandem mass spectrometric experiments on a Fourier transform ion cyclotron resonance mass spectrometer by application of sustained off-resonance irradiation (SORI) on a selected tetrameric charge state. The technique of single-frequency quadrupole excitation was used to accomplish selected-ion accumulation of the 14 + charge state of the tetramer during ion injection. Subsequent low energy SORI combined with broadband quadrupole cooling produced the 7 + monomer and 7 + trimer species, as well as the 6 + monomer and 8 + trimer complementary ions. The observed asymmetric breakup of the tetramer is qualitatively explained by using physical models.
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