New Publication: Effects of drift gas selection on the ambient-temperature, ion mobility mass spectrometry analysis of amino acids

Effects of drift gas selection on the ambient-temperature, ion mobility mass spectrometry analysis of amino acids. Kimberly L. Davidson and Matthew F. Bush. Anal. Chem. 2017, DOI: 10.1021/acs.analchem.6b04605. (Link)

Ion mobility (IM) separates ions based on their response to an electric field in the presence of a drift gas. Due to its speed and sensitivity, the integration of IM and mass spectrometry (MS) offers many potential advantages for the analysis of small molecules. To determine the effects that drift gas selection has on the information content of IM separations, absolute collision cross sections (Ω) with He, N2, Ar, CO2, and N2O were measured for the 20 common amino acids using low-pressure, ambient-temperature ion mobility experiments performed in a radio-frequency-confining drift cell. Continue reading

Analyst Most Accessed Articles in 2016

Congratulations to Sam Allen, whose article was one of the top 25 most downloaded articles published in the Analyst in 2016. That article is now featured in the Analyst 2016 Most Accessed Articles Collection.

  • Ion mobility mass spectrometry of peptide, protein, and protein complex ions using a radio-frequency confining drift cell. Samuel J. Allen, Kevin Giles, Tony Gilbert, Matthew F. Bush. Analyst 2016141, 884-891. (Link|PUBMED|PDF)

New Instrument

We are fabricating a new instrument for ion mobility mass spectrometry, which was designed by Sam Allen and Rae Eaton. Here is a video of some recent work by the machine shop in UW Department of Chemistry.

New Lab Member: Julia Greenwald

The Bush Lab welcomes Julia Greenwald! Click here to learn more about Julia.

New Publication: Nonspecific aggregation in native electrokinetic nanoelectrospray ionization

Droplets_TOCNonspecific Aggregation in Native Electrokinetic Nanoelectrospray Ionization. Kimberly L. Davidson; Derek R. Oberreit; Christopher J. Hogan; Matthew F. Bush. Int. J. Mass Spectrom. 2016, DOI: 10.1016/j.ijms.2016.09.013. (Link)

Native mass spectrometry is widely used to determine the stoichiometries and binding constants of noncovalent interactions in solution. One challenge is that multiple analytes in a single electrospray droplet can aggregate during solvent evaporation, which will bias the distribution of oligomeric states observed during gas-phase measurements. Here, measurements of solution flow rates, electrospray currents, droplet size distributions, and nonspecific aggregation are used in conjunction with Poisson statistics to characterize the factors that control nonspecific aggregation during typical native mass spectrometry experiments. Continue reading

New Publication: Analysis of Native-Like Ions Using Structures for Lossless Ion Manipulations

slim_tocAnalysis of Native-Like Ions using Structures for Lossless Ion Manipulations.
Samuel J. Allen, Rachel M. Eaton, and Matthew F. Bush.
Anal. Chem. 2016, DOI: 10.1021/acs.analchem.6b02089. (Link)

Ion mobility separation of native-like protein and protein complex ions expands the structural information available through native mass spectrometry analysis. Here, we implement Structures for Lossless Ion Manipulations (SLIM) for the analysis of native-like ions. SLIM has been shown previously to operate with near lossless transmission of ions up to 3000 Da in mass. Here for the first time, SLIM was used to separate native-like protein and protein complex ions ranging in mass from 12 to 145 kDa. The resulting arrival-time distributions were monomodal and were used to determine collision cross section values that are within 3% of those determined from radio-frequency-confining drift cell measurements. These results are consistent with the retention of native-like ion structures throughout these experiments. Continue reading

New Publication: Radio-Frequency (rf) Confinement in Ion Mobility Spectrometry

rf_cofinement_toc_2Radio-Frequency (rf) Confinement in Ion Mobility Spectrometry: Apparent Mobilities and Effective Temperatures
Samuel J. Allen, Matthew F. Bush
J. Am. Soc. Mass Spectrom. 2016, DOI: 10.1007/s13361-016-1479-9. (Link)

Ion mobility is a powerful tool for separating and characterizing the structures of ions. Here, a radio-frequency (rf) confining drift cell is used to evaluate the drift times of ions over a broad range of drift field strengths (E/P, V cm–1 Torr–1). The presence of rf potentials radially confines ions and results in excellent ion transmission at low E/P (less than 1 V cm–1 Torr–1), thereby reducing the dependence of ion transmission on the applied drift voltage. Non-linear responses between drift time and reciprocal drift voltages are observed for extremely low E/P and high rf amplitudes. Under these conditions, pseudopotential wells generated by the rf potentials dampen the mobility of ions. The effective potential approximation Continue reading

New Publication: Folding of Protein Ions in the Gas Phase after Cation-to-Anion Proton-Transfer Reactions (CAPTR)

Folding of Protein Ions in the Gas Phase after Cation-to-Anion Proton-Transfer Reactions (CAPTR)
Kenneth J Laszlo, Eleanor B. Munger, and Matthew F Bush
J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.6b04282. (Link)

The structure and folding of a protein in solution depends on noncovalent interactions within the protein and those with surrounding ions and molecules. Decoupling these interactions in solution is challenging, which has hindered the development of accurate physics-based models for structure prediction. Investigations of proteins in the gas phase can be used to selectively decouple factors affecting the structures of proteins. Here, we use Cation to Anion Proton Transfer Reactions (CAPTR) to reduce the charge states of denatured ubiquitin ions in the gas phase, and ion mobility to probe their structures. Continue reading

New Lab Member: Anna Bakhtina

anna_thumbnailThe Bush Lab welcomes Anna Bakhtina, who is an undergraduate biochemistry major. Click here to learn more about Anna.

New Lab Member: Jack Buckner

jackThe Bush Lab welcomes Jack Buckner, who is visiting this summer from Carleton College. Click here to learn more about Jack.