Development of gas-phase ion mobility separation methods combined with mass spectrometry for the analysis of biological mixtures

Ion mobility techniques coupled with electrospray ionization (ESI)-mass spectrometry (MS) methods have been used to study the conformations of a wide variety of biological ions in the absence of solvent.{09}One intriguing possibility that has arisen from these studies is the use of the gas phase as a medium for rapid and sensitive characterization of biomolecular mixtures. This has been realized in the last several years due to developments in the combination of ion mobility and mass spectrometry techniques. Inherent limitations in the sensitivity of ion mobility methods arise due to coupling the continuous ESI source with the pulsed mobility experiment. An ion trap interface for storage of ions prior to the mobility experiment was incorporated to address the low sensitivity of the technique. Additionally, an ion mobility/time-of-flight method that allows all mobility-separated ions to be dispersed by differences in their m/z ratios has been developed.{09}This method allows for the direct measurement of m/z and conformer-resolved abundance information for the total ion system. Higher resolution measurements have been made possible with the development of a high-pressure high-resolution ion mobility spectrometer. This instrument allows complex biological mixtures to be analyzed in greater detail. Primary sequence information, obtained from multiple stages of MS, has become increasingly important for the analysis of complex mixtures. Typically, some form of liquid chromatography is coupled with tandem MS to decrease the complexity of the mixture prior to MS/MS analysis. An injected-ion mobility/TOF mass spectrometer that provides a gas-phase separation and parallel sequence information for mobility-separated ions has been designed, constructed, and utilized. Although these technologies are still at an early stage of development, they have been shown to provide some unique advantages in the analysis of complex biological mixtures.