Tandem mass spectrometry

Tandem mass spectrometry selects precursor ions, fragments them, and analyzes the resulting product ions. It reveals molecular structure and composition through linked stages of mass analysis.

Precursor ion: An ion selected for fragmentation or further analysis in a mass spectrometer. It is the selected starting ion whose fragments tandem analysis measures.
Tandem mass tag: An isobaric chemical label used to quantify proteins across multiple samples by tandem mass spectrometry. It enables multiplexed protein quantification from product-ion reporter signals.
Mass spectrometry: An analytical technique that measures ions according to their mass-to-charge ratios. Tandem analysis extends mass spectrometry by linking multiple stages of measurement.
Tandem-in-time mass spectrometry: A tandem mass spectrometry arrangement that performs ion selection, fragmentation, and analysis sequentially in one device. It contrasts with instruments that carry out stages in separate spatial regions.
Peptide sequencing: The determination of the amino-acid order in a peptide. Fragment-ion series can reveal peptide sequence without directly sequencing the intact protein.
Product ion: An ion formed from another ion through fragmentation or a chemical reaction. Its mass and abundance provide the measured evidence after precursor fragmentation.
Multiple reaction monitoring: A targeted mass spectrometry method that monitors selected precursor-to-product ion transitions. It uses defined ion transitions for sensitive, quantitative assays.
Electrospray ionization: An ionization technique that produces gas-phase ions from charged droplets formed from a liquid. It commonly supplies molecular ions for tandem analysis of large, polar molecules.
Electron-transfer dissociation: An ion fragmentation method in which electron transfer to a multiply charged cation induces dissociation. It offers a fragmentation route distinct from collision-driven activation, often preserving labile modifications.
Metabolomics: The systematic study of small molecules in biological systems. Tandem spectra help identify metabolites among chemically diverse mixtures.

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