title: Importance of structural tightening, as opposed to partially bound States, in the determination of chemical shift changes at noncovalently bonded interfaces.
abstract: Two models (A and B) have been proposed to account for decreased downfield chemical shifts of a proton bound by noncovalent interactions at a ligand/antibiotic interface as the number of ligand/antibiotic interactions is decreased. In model A, the proton involved in the noncovalent bond suffers a smaller downfield shift because the bond is, with a relatively large probability, broken, and not because it is longer. In model B, the proton involved in the noncovalent bond suffers a smaller downfield shift because the bond is longer, and not because it is, with a relatively large probability, broken. We show that model A cannot account for the chemical shift changes. Model B accounts for the process of positively cooperative binding, in which noncovalent bonds are reduced in length and thereby increase the stability of the organized state.
authors.affiliation: Department of Chemistry, Lensfield Road, Cambridge, CB2 1EW, UK.
authors.forename: Dudley H
authors.initials: DH
authors.lastname: Williams
authors.forename: Nichola L
authors.initials: NL
authors.lastname: Davies
authors.forename: Jari J
authors.initials: JJ
authors.lastname: Koivisto
mesh_terms: D001665:Binding Sites; D006860:Hydrogen Bonding; D007700:Kinetics; D008956:Models, Chemical; D019906:Nuclear Magnetic Resonance, Biomolecular; D009842:Oligopeptides / Q000737:chemistry* / Q000378:metabolism; D012310:Ristocetin / Q000737:chemistry* / Q000378:metabolism; D013816:Thermodynamics; D014640:Vancomycin / Q000031:analogs & derivatives* / Q000737:chemistry* / Q000378:metabolism
chemical_list: D009842:Oligopeptides; C112142:chloroeremomycin; D012310:Ristocetin; C016719:ristocetin A; C043367:lysyl-alanyl-alanine; D014640:Vancomycin