Abstract
We have previously demonstrated native liquid extraction surface analysis (LESA) mass spectrometry imaging of small intact proteins in thin tissue sections. We also showed calculation of collision cross sections for specific proteins extracted from discrete locations in tissue by LESA traveling wave ion mobility spectrometry (TWIMS). Here, we demonstrate an integrated native LESA TWIMS mass spectrometry imaging (MSI) workflow, in which ion mobility separation is central to the imaging experiment and which provides spatial, conformational, and mass information on endogenous proteins in a single experiment. The approach was applied to MSI of a thin tissue section of mouse kidney. The results show that the benefits of integration of TWIMS include improved specificity of the ion images and the capacity to calculate collision cross sections for any protein or protein complex detected in any pixel (without a priori knowledge of the presence of the protein).
Highlights
Native mass spectrometry enables the analysis of tertiary and quaternary protein structure in the gas phase.[1]
Traveling wave ion mobility spectrometry (TWIMS) has found widespread use for over a decade since the introduction of commercially available traveling wave ion mobility spectrometry (TWIMS)-enabled mass spectrometers.[5−9] Structural information may be inferred from collision cross section (CCS) values derived from drift tube ion mobility spectrometry (DTIMS) or calibrated TWIMS measurements.[10]
Mouse tissue was analyzed by contact liquid extraction surface analysis (LESA) TWIMS-mass spectrometry imaging (MSI) under native conditions
Summary
Native mass spectrometry enables the analysis of tertiary and quaternary protein structure in the gas phase.[1] Noncovalent interactions such as hydrogen bonds and salt bridges that were present in solution are preserved in the gas phase through the use of mild electrospray ionization conditions including nativelike solvents. Liquid extraction surface analysis (LESA) MS is an ambient surface sampling technique that is suited to the direct analysis of intact proteins from biological substrates.[16,17] LESA mass spectrometry imaging (MSI) allows the spatial distribution of analytes, including proteins, to be mapped.[18] As LESA MS makes use of electrospray ionization, the technique is suitable for native mass spectrometry through use of nativelike solvents.
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