Integration of Trapped Ion Mobility Spectrometry and Ultraviolet Photodissociation in a Quadrupolar Ion Trap Mass Spectrometer

There is a growing demand for lower-cost, benchtop analyticalinstrumentswith complementary separation capabilities for the screening and characterizationof biological samples. In this study, we report on the custom integrationof trapped ion mobility spectrometry and ultraviolet photodissociationcapabilities in a commercial Paul quadrupolar ion trap multistagemass spectrometer (TIMS-QIT-MSn UVPD platform). A gatedTIMS operation allowed for the accumulation of ion mobility separatedion in the QIT, followed by a mass analysis (MS1 scan) or m/z isolation, followed by selected collisioninduced dissociation (CID) or ultraviolet photodissociation (UVPD)and a mass analysis (MS2 scan). The analytical potential of this platformfor the analysis of complex and labile biological samples is illustratedfor the case of positional isomers with varying PTM location of thehistone H4 tryptic peptide 4-17 singly and doubly acetylated and thehistone H3.1 tail (1-50) singly trimethylated. For all cases, a baselineion mobility precursor molecular ion preseparation was obtained. Thetandem CID and UVPD MS2 allowed for effective sequence confirmationas well as the identification of reporter fragment ions associatedwith the PTM location; a higher sequence coverage was obtained usingUVPD when compared to CID. Different from previous IMS-MS implementation,the novel TIMS-QIT-MSn UVPD platform offers a lower-costalternative for the structural characterization of biological moleculesthat can be widely disseminated in clinical laboratories.