title: Unfolding of Hydrated Alkyl Diammonium Cations Revealed by Cryogenic Ion Mobility-Mass Spectrometry.
abstract: Hydration of the ammonium ion plays a key role in determining the biomolecular structure as well as local structure of water in aqueous environments. Experimental data obtained by cryogenic ion mobility-mass spectrometry (cryo-IM-MS) show that dehydration of alkyl diammonium cations induces a distinct unfolding transition at a critical number of water molecules, n = 21 to 23, n = 24 to 26, and n = 27 to 29, for 1,7-diaminoheptane, 1,8-diaminooctane, and 1,10-diaminodecane, respectively. Results are also presented that reveal compelling evidence for unique structural transitions of hydrated ammonium ions associated with the development of the hydrogen-bond network around individual charged groups. The ability to track the evolution of structure upon stepwise dehydration provides direct insight into the intricate interplay between solvent-molecule interactions that are responsible for defining conformations. Such insights are potentially valuable in understanding how ammonium ion solvation influences conformation(s) of larger biomolecules.
authors.forename: Kelly A
authors.initials: KA
authors.lastname: Servage
authors.forename: Kyle L
authors.initials: KL
authors.lastname: Fort
authors.forename: Joshua A
authors.initials: JA
authors.lastname: Silveira
authors.affiliation: ‡Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States.
authors.forename: Liuqing
authors.initials: L
authors.lastname: Shi
authors.affiliation: ‡Department of Chemistry, Indiana University, Bloomington, Indiana 47405, United States.
authors.forename: David E
authors.initials: DE
authors.lastname: Clemmer
authors.forename: David H
authors.initials: DH
authors.lastname: Russell
mesh_terms: D002412:Cations / Q000737:chemistry; D003959:Diamines / Q000737:chemistry*; D005615:Freezing; D021241:Spectrometry, Mass, Electrospray Ionization; D014867:Water / Q000737:chemistry*
chemical_list: C065351:1,10-diaminodecane; D002412:Cations; D003959:Diamines; D014867:Water; C008697:octamethylenediamine; C015127:1,7-diaminoheptane