Tandem Mass Spectrometry

Tandem mass spectrometry (MS/MS) is a method to obtain sequence and structural information by measurement of the mass-to-charge ratios of ionized peptide molecules before and after dissociation reactions within a mass spectrometer which consists essentially of two mass spectrometers in tandem. In the first step, a mass filter (quadrupole) allows only selected ions (parent or precursor ions) to reach the collision cell. In the collision cell, the peptide is further fragmented by energy impact with a collision gas (argon). The generated daughter or product ions can be analyzed by a second mass filter (quadrupole, time-of-flight). MS/MS measurements can be performed with triple quadrupole mass spectrometry (MS), ion trap MS or more recently with quadrupole-time-of-flight MS. MS/MS spectra of peptides mainly show sequence-specific N-terminal “b” and C-terminal “y” ions and can be used to identify proteins from databases.

Proteomics