title: Investigation of the Complete Suite of the Leucine and Isoleucine Isomers: Toward Prediction of Ion Mobility Separation Capabilities.
abstract: In this study we investigated 11 isomers with the molecular formula C6H13NO2(m/z 131) to ascertain the potential of utilizing drift tube ion mobility mass spectrometry to aid in the separation of isomeric mixtures. This study of small molecules provides a detailed examination of the application of uniform field ion mobility for a narrow scope of isomers with variations in both bond coordination and stereochemistry. For small molecules, it was observed that in general constitutional isomers are more readily separated by uniform field mobility in comparison to stereoisomers such as enantiomers or diastereomers. Diastereomers exhibited differences in their collision cross section (CCS), but were unresolvable in a mixture, whereas the enantiomers studied did not exhibit statistically different CCS values. A mathematical relationship relating the CCS to resolving power was developed in order to predict the required ion mobility resolving power needed to separate the various isomer classes. For the majority of isomers evaluated in this study, a uniform field-based resolving power of 100 was predicted to be sufficient to resolve over half (∼60%) of all hypothetical isomer pairs, including leucine and isoleucine, whereas their stereoisomers (d- and l-forms) are predicted to be significantly more challenging, if not impossible, to separate by conventional drift tube techniques.
authors.affiliation: Department of Chemistry, Center for Innovative Technology, Vanderbilt Institute of Chemical Biology, Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University , Nashville, Tennessee 37235, United States.
authors.forename: James N
authors.initials: JN
authors.lastname: Dodds
authors.affiliation: Department of Chemistry, Center for Innovative Technology, Vanderbilt Institute of Chemical Biology, Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University , Nashville, Tennessee 37235, United States.
authors.forename: Jody C
authors.initials: JC
authors.lastname: May
authors.affiliation: Department of Chemistry, Center for Innovative Technology, Vanderbilt Institute of Chemical Biology, Vanderbilt Institute for Integrative Biosystems Research and Education, Vanderbilt University , Nashville, Tennessee 37235, United States.
authors.forename: John A
authors.identifier: 0000-0001-8918-6419
authors.initials: JA
authors.lastname: McLean
mesh_terms: D007532:Isoleucine / Q000032:analysis*; D007536:Isomerism; D007930:Leucine / Q000032:analysis*; D013058:Mass Spectrometry; D008968:Molecular Conformation
chemical_list: D007532:Isoleucine; D007930:Leucine