Internal calibrants allow high accuracy peptide matching between MALDI imaging MS and LC-MS/MS
Date
2012
Authors
Gustafsson, O.
Eddes, J.
Meding, S.
Koudelka, T.
Oehler, M.
McColl, S.
Hoffmann, P.
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Journal article
Citation
Journal of Proteomics, 2012; 75(16):5093-5105
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Johan O.R. Gustafsson, James S. Eddes, Stephan Meding, Tomas Koudelka, Martin K. Oehler, Shaun R. McColl and Peter Hoffmann
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Abstract
One of the important challenges for MALDI imaging mass spectrometry (MALDI-IMS) is the unambiguous identification of measured analytes. One way to do this is to match tryptic peptide MALDI-IMS m/z values with LC-MS/MS identified m/z values. Matching using current MALDI-TOF/TOF MS instruments is difficult due to the variability of in situ time-of-flight (TOF) m/z measurements. This variability is currently addressed using external calibration, which limits achievable mass accuracy for MALDI-IMS and makes it difficult to match these data to downstream LC-MS/MS results. To overcome this challenge, the work presented here details a method for internally calibrating data sets generated from tryptic peptide MALDI-IMS on formalin-fixed paraffin-embedded sections of ovarian cancer. By calibrating all spectra to internal peak features the m/z error for matches made between MALDI-IMS m/z values and LC-MS/MS identified peptide m/z values was significantly reduced. This improvement was confirmed by follow up matching of LC-MS/MS spectra to in situ MS/MS spectra from the same m/z peak features. The sum of the data presented here indicates that internal calibrants should be a standard component of tryptic peptide MALDI-IMS experiments.
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© 2012 Elsevier B.V. All rights reserved.