Development of Native MS Capabilities on an Extended Mass Range Q-TOF MS.

Native mass spectrometry (nMS) is increasingly used for studies of large biomolecules (>100 kDa), especially proteins and protein complexes. The growth in this area can be attributed to advances in native electrospray ionization as well as instrumentation that is capable of accessing high mass-to-charge (m/z) regimes without significant losses in sensitivity and resolution. Here, we describe modifications to the ESI source of an Agilent 6545XT Q-TOF MS that is tailored for analysis of large biomolecules. The modified ESI source was evaluated using both soluble and membrane protein complexes ranging from ~127 to ~232 kDa and the ~801 kDa protein chaperone GroEL. The increased mass resolution of the instrument affords the ability to resolve small molecule adducts and analyze collision-induced dissociation products of the native complexes.