title: Experimental and Theoretical Investigation of Sodiated Multimers of Steroid Epimers with Ion Mobility-Mass Spectrometry.
abstract: Ion mobility-mass spectrometry (IM-MS) has recently seen increased use in the analysis of small molecules, especially in the field of metabolomics, for increased breadth of information and improved separation of isomers. In this study, steroid epimers androsterone and trans-androsterone were analyzed with IM-MS to investigate differences in their relative mobilities. Although sodiated monomers exhibited very similar collision cross-sections (CCS), baseline separation was observed for the sodiated dimer species (RS= 1.81), with measured CCS of 242.6 and 256.3 Å2, respectively. Theoretical modeling was performed to determine the most energetically stable structures of solution-phase and gas-phase monomer and dimer structures. It was revealed that these epimers differ in their preferred dimer binding mode in solution phase: androsterone adopts a R=O - Na+- OH-R' configuration, whereas trans-androsterone adopts a R=O - Na+- O=R' configuration. This difference contributes to a significant structural variation, and subsequent CCS calculations based on these structures relaxed in the gas phase were in agreement with experimentally measured values (ΔCCS ~ 5%). Additionally, these calculations accurately predicted the relative difference in mobility between the epimers. This study illustrates the power of combining experimental and theoretical results to better elucidate gas-phase structures. Graphical Abstract ᅟ.
authors.affiliation: Department of Chemistry, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Chouinard
authors.affiliation: Department of Chemistry, University of Florida, Gainesville, FL, 32611, USA.|CAPES Foundation, Ministry of Education of Brazil, Brasília, DF, 70040-020, Brazil.
authors.forename: Vinícius Wilian D
authors.initials: VWD
authors.lastname: Cruzeiro
authors.affiliation: Department of Chemistry, University of Florida, Gainesville, FL, 32611, USA.
authors.forename: Adrian E
authors.initials: AE
authors.lastname: Roitberg
authors.affiliation: Department of Chemistry, University of Florida, Gainesville, FL, 32611, USA. ryost@chem.ufl.edu.|Southeast Center for Integrated Metabolomics (SECIM), University of Florida, Gainesville, FL, 32611, USA. ryost@chem.ufl.edu.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Yost
keywords: Collision cross-sections (CCS); Ion mobility-mass spectrometry (IM-MS); Isomers; Steroids; Theoretical modeling