title: MeCAT--comparing relative quantification of alpha lactalbumin using both molecular and elemental mass spectrometry.
abstract: 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.
authors: Applied Analytical and Environmental Chemistry, Department of Chemistry, Humboldt-Universitaet zu Berlin, Brook-Taylor Str. 2, 12489 Berlin, Germany.
authors: Gunnar
authors: G
authors: Schwarz
authors: Sebastian
authors: S
authors: Beck
authors: David
authors: D
authors: Benda
authors: Michael W
authors: MW
authors: Linscheid
mesh_terms: D000345:Affinity Labels; D002851:Chromatography, High Pressure Liquid; D002853:Chromatography, Liquid; D007477:Ions / Q000737:chemistry; D007553:Isotope Labeling; D007768:Lactalbumin / Q000032:analysis* / Q000737:chemistry*; D028581:Lanthanoid Series Elements / Q000737:chemistry; D013058:Mass Spectrometry / Q000379:methods*; D010455:Peptides / Q000032:analysis / Q000737:chemistry; D013054:Spectrophotometry, Atomic
chemical_list: D000345:Affinity Labels; D007477:Ions; D028581:Lanthanoid Series Elements; D010455:Peptides; D007768:Lactalbumin