MeCAT--comparing relative quantification of alpha lactalbumin using both molecular and elemental mass spectrometry

Chemical tagging with stable isotopes is one of the best established methods for the quantification of proteins using mass spectrometry, especially in non-proliferating cells and tissue. The absolute quantification of proteins is still a challenge. Metal-coded affinity tagging (MeCAT), used to label...

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Bibliographic Details
Published in:Analyst (London) 2013-04, Vol.138 (8), p.2449-2455
Main Authors: Schwarz, Gunnar, Beck, Sebastian, Benda, David, Linscheid, Michael W
Format: Article
Language:English
Subjects:
Affinity Labels
Chromatography, High Pressure Liquid
Chromatography, Liquid
Inductively coupled plasma
Infrared
Ions - chemistry
Isotope Labeling
Lactalbumin - analysis
Lactalbumin - chemistry
Lanthanides
Lanthanoid Series Elements - chemistry
Marking
Mass spectrometry
Mass Spectrometry - methods
Multiplexing
Peptides
Peptides - analysis
Peptides - chemistry
Proteins
Spectrophotometry, Atomic
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Summary:Chemical tagging with stable isotopes is one of the best established methods for the quantification of proteins using mass spectrometry, especially in non-proliferating cells and tissue. The absolute quantification of proteins is still a challenge. Metal-coded affinity tagging (MeCAT), used to label proteins and peptides with lanthanide ions, allows both, relative and absolute, quantitative determination. MeCAT loaded with lanthanide ions allows the use of inductively coupled plasma mass spectrometry (ICP-MS) enabling very accurate and sensitive quantification of peptides and proteins based on the metal ion signal. Furthermore, multiplex assays are possible that are not limited to 4- or 8-plex analyses when using different lanthanides. Naturally, different lanthanides also lead to different molecular masses for the same labelled peptides which can be distinguished easily. This enables the relative quantification in electrospray MS based on the relative signal intensities of the differentially labelled peptides. We have studied MeCAT labelled peptides, using LC/ESI-MS and LC/ESI-MS/MS with infrared multiphoton dissociation (IRMPD) to show that both the molecular masses and the specific fragments resulting from the MS/MS experiments can be used for relative quantification. The results are compared with high performance liquid chromatography (HPLC)/ICP-MS and direct ICP-MS analysis as standard methods. We show that the ESI and IRMPD based methods deliver quantitative results comparable to ICP-MS.
ISSN:0003-2654
1364-5528
DOI:10.1039/c3an36602b