Multiplexed analysis of peptide functionality using lanthanide-based structural shift reagents

Functionally selective lanthanide-based ion mobility shift reagents are presented as a method to elucidate protein or peptide structural information as well as relative quantitation of protein expression profiles. Sequence information and site localization of primary amines (n-terminus and lysine), phosphorylation sites, and cysteine residues can be obtained in a data dependent manner using ion mobility-mass spectrometry (IM-MS). The high mass of the incorporated lanthanide ensures a significant shift of where the signal occurs in IM-MS conformation space. Peptide sequence information provided by the use of IM-MS shift reagents allows for both a more confident identification of peptides from complex mixtures and site localization following tandem MS experiments. Stable isotopes of the lanthanide series may also be used as relative quantitation labels since several lanthanides can be utilized in differential sample analyses.