title: Gas phase stabilization of noncovalent protein complexes formed by electrospray ionization.
abstract: The use of gas phase additives to stabilize noncovalent protein complexes in electrospray ionization mass spectrometry (ES-MS) is demonstrated for two protein-ligand interactions, an enzyme-small molecule inhibitor complex, and a protein-disaccharide complex. It is shown that the introduction of gas phase imidazole into the ES ion source effectively protects gas phase protein-ligand complexes against in-source dissociation. The stabilizing effect of imidazole vapor is comparable to that observed upon addition of imidazole to the ES solution. The introduction of sulfur hexafluoride, at high partial pressure, into the source region also effectively suppresses in-source dissociation of protein complexes. It is proposed that evaporative cooling is the primary mechanism responsible for the stabilizing effects observed for the gas phase additives.
authors.affiliation: Molecular Structure, Amgen, Thousand Oaks, California 91320, USA.
authors.forename: Dhanashri
authors.initials: D
authors.lastname: Bagal
authors.forename: Elena N
authors.initials: EN
authors.lastname: Kitova
authors.forename: Lan
authors.initials: L
authors.lastname: Liu
authors.forename: Amr
authors.initials: A
authors.lastname: El-Hawiet
authors.forename: Paul D
authors.initials: PD
authors.lastname: Schnier
authors.forename: John S
authors.initials: JS
authors.lastname: Klassen
mesh_terms: D000818:Animals; D001550:Benzamidines / Q000737:chemistry; D002417:Cattle; D004187:Disaccharides / Q000737:chemistry; D005740:Gases / Q000737:chemistry*; D007093:Imidazoles / Q000737:chemistry; D008024:Ligands; D011506:Proteins / Q000737:chemistry*; D015842:Serine Proteinase Inhibitors / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013459:Sulfur Hexafluoride / Q000737:chemistry; D014357:Trypsin / Q000737:chemistry
chemical_list: D001550:Benzamidines; D004187:Disaccharides; D005740:Gases; D007093:Imidazoles; D008024:Ligands; D011506:Proteins; D015842:Serine Proteinase Inhibitors; C029899:imidazole; D014357:Trypsin; C032157:benzamidine; D013459:Sulfur Hexafluoride