title: A crystallographic titration of the dipeptide L-isoleucyl-L-isoleucine.
abstract: The dipeptide L-Ile-L-Ile has been crystallized in four different protonation states, including as a cation, a zwitterion and an anion, as well as a dimeric cation in which two peptide molecules, linked by a strong -COO...H...OOC- hydrogen bond, share an overall positive charge of +1. This unprecedented series of crystal structures exhibits differences in hydrogen-bonding capabilities, conformational properties and molecular packing arrangements. The crystallization of L-Ile-L-Ile as an anion was achieved by slow evaporation from an NH(3)(l) solution to give the first ever ammonium salt of a peptide (or amino acid).
authors.affiliation: Department of Chemistry, University of Oslo, PO Box 1033 Blindern, N-0315 Oslo, Norway. c.h.gorbitz@kjemi.uio.no
authors.forename: Carl Henrik
authors.initials: CH
authors.lastname: Görbitz
mesh_terms: D000838:Anions / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D018360:Crystallography, X-Ray; D004151:Dipeptides / Q000737:chemistry* / Q000302:isolation & purification; D006860:Hydrogen Bonding; D007532:Isoleucine / Q000737:chemistry; D008958:Models, Molecular; D011487:Protein Conformation
chemical_list: D000838:Anions; D002412:Cations; D004151:Dipeptides; D007532:Isoleucine