Poster abstracts
Poster number 96 submitted by Zachary Smith
The Effect of FT Transient Length on Measured SID Product Ion Intensities
Zachary D Smith (Biophysics Graduate Program), Andrew J. Arslanian (Department of Chemistry and Biochemistry), Arpad Somogyi (Department of Chemistry and Biochemistry), Vicki H. Wysocki (Department of Chemistry and Biochemistry)
Abstract:
Sometimes overlooked in the structural biology field, mass spectrometry (MS) serves as a simple approach for stoichiometry and connectivity measurements in a biochemical study with low sample consumption and fills lapses in traditional techniques. Designed for large m/z ions, the Q Exactive Ultra-High Mass Range (UHMR) Hybrid Quadrupole Orbitrap Mass Spectrometer is on the market for quaternary structure determination.1,2 Ideally, the detector in a mass spectrometer is expected to be ion independent. In the UHMR, detection typically occurs using image charge current vs time, and the time-domain signal is Fourier transformed to the frequency domain and converted to the m/z domain. However, discrepancies in ion detection depending on acquisition time occurred, likely due to charge state and the ion’s size. The protein complexes streptavidin and pyruvate kinase show differing spectra based on the time domain transient length. Surface-induced dissociation separated each protein complex into various oligomeric states and spectra at differing transient lengths were recorded. Pyruvate kinase, a tetrameric protein complex, dissociates by SID to form monomers, dimers, and trimers. When collecting spectra at transient lengths of 40 ms, 80 ms, and 160 ms, relative signal intensities fluctuated for the oligomeric products. With transient lengths 320 ms and greater, the spectra have stable product ion ratios. As a control, charge detection mass spectrometry, shown to be highly effective for large complexes, gave a baseline for ion abundances.3 The CDMS results indicate that the spectra in the normal mode do not fully reflect the correct ion ratios at any transient length. Regarding the changing of ion abundances with transient length, a bias exists against large species at long transient lengths,4 and researchers were advised to set a short transient length for most applications5. This study investigates the effect of transient recording times on ion detection to better understand why detections are different between spectra and when this effect is present.
References:
1) Makarov, A.; Denisov, E. J. Am. Soc. Mass Spectrom. 2009, 20 (8), 1486–1495. https://doi.org/10.1016/j.jasms.2009.03.024
2) Makarov, A.; Denisov, E.; Lange, O. J. Am. Soc. Mass Spectrom. 2009, 20 (8), 1391–1396. doi.org/10.1016/j.jasms.2009.01.005
3) Deslignière, E., Yin, V.C., Ebberink, E.H.T.M. et al. Nat Methods (2024). https://doi.org/10.1038/s41592-024-02207-8
4) Snyder, D. T.; Panczyk, E. M.; Somogyi, A.; Kaplan, D. A.; Wysocki V. H. Analytical Chemistry 2020 92 (16), 11195-11203. DOI: 10.1021/acs.analchem.0c01657
5) VanAernum, Z. L.; Gilbert, J. D.; Belov, M. E.; Makarov, A.; Horning, S. R.; Wysocki, V. H. Analytical Chemistry 2019 91 (5), 3611-3618. DOI: 10.1021/acs.analchem.8b05605
Keywords: Mass Spectrometry