PNNL

Abstract

Methods are being developed for ultra-sensitive protein characterization based upon electrospray ionization (ESI) with Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). The sensitivity of a FTICR mass spectrometer equipped with an ESI source depends on the overall ion transmission, which combines the probability of ionization and transmission efficiency itself and the probability of ion trapping in the FTICR cell. Our developments using a 3.5 tesla FTICR mass spectrometer include introduction and optimization of a newly designed electrodynamic ion funnel in the ESI interface, improving the ion beam characteristics in a quadrupole-electrostatic ion guide interface as well as modification of the electrostatic ion guide. These developments provide a detection limit of approximately 30 zmol (-18,000 molecules) for proteins with molecular weights ranging from 8 to 20 kDa.