title: Gas phase hydrogen/deuterium exchange of arginine and arginine dipeptides complexed with alkali metals.
abstract: The hydrogen/deuterium (H/D) exchange of protonated and alkali-metal cationized Arg-Gly and Gly-Arg peptides with D(2)O in the gas phase was studied using electrospray ionization quadropole ion trap mass spectrometry. The Arg-Gly and Gly-Arg alkali metal complexes exchange significantly more hydrogens than protonated Arg-Gly and Gly-Arg. We propose a mechanism where the peptide shifts between a zwitterionic salt bridge and nonzwitterionic charge solvated conformations. The increased rate of H/D exchange of the alkali metal complexes is attributed to the peptide metal complexes' small energy difference between the salt-bridge conformation and the nonzwitterionic charge-solvated conformation. Implications for the applicability of this mechanism to other zwitterionic systems are discussed.
authors.affiliation: Department of Chemistry, Grinnell College, Grinnell, Iowa 50112, USA.
authors.forename: Laura A
authors.initials: LA
authors.lastname: Mertens
authors.forename: Elaine M
authors.initials: EM
authors.lastname: Marzluff
mesh_terms: D001120:Arginine / Q000737:chemistry* / Q000378:metabolism; D002627:Chemistry, Physical / Q000379:methods*; D003903:Deuterium / Q000737:chemistry* / Q000378:metabolism; D004151:Dipeptides / Q000737:chemistry* / Q000378:metabolism; D005740:Gases / Q000737:chemistry; D005998:Glycine / Q000737:chemistry* / Q000378:metabolism; D006859:Hydrogen / Q000737:chemistry* / Q000378:metabolism; D007474:Ion Exchange; D008672:Metals, Alkali / Q000737:chemistry; D008958:Models, Molecular; D008968:Molecular Conformation; D011522:Protons; D012492:Salts; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D004151:Dipeptides; D005740:Gases; D008672:Metals, Alkali; D011522:Protons; D012492:Salts; D006859:Hydrogen; D001120:Arginine; D003903:Deuterium; D005998:Glycine