title: Conformations of gas-phase ions of ubiquitin, cytochrome c, apomyoglobin, and beta-lactoglobulin produced from two different solution conformations.
abstract: At low pH in solutions of 50% methanol, proteins form expanded denatured states (the "H" state). In 90% methanol, proteins form expanded helical denatured states with artificial alpha-helices (the "H(c)" state). Gas-phase ions of ubiquitin, cytochrome c, apomyoglobin, and native and disulfide-reduced beta-lactoglobulin were formed by electrospray ionization (ESI) of the proteins from the H and H(c) states in solution. Both states in solution produce the same charge states in ESI. The conformations of the ions were studied with cross section measurements and gas-phase H/D exchange experiments. The cross sections show that the ions retain considerable folded structure. For a given protein and given charge state, ions produced from the H and H(c) states showed the same cross sections (within approximately 1%). Ions of cytochrome c, apomyoglobin, and native and reduced beta-lactoglobulin of a given charge state showed no differences in H/D exchange level when produced from the H or H(c) state. However, ubiquitin ions produced from the H(c) state consistently exchange fewer ( approximately 13%) hydrogens than ions produced from the H state, suggesting that in this case the gas-phase protein ions retain some memory of their solution conformations.
authors: Department of Chemistry, University of British Columbia, Vancouver, British Columbia, Canada.
authors: P John
authors: PJ
authors: Wright
authors: Jianmin
authors: J
authors: Zhang
authors: D J
authors: DJ
authors: Douglas
mesh_terms: D000818:Animals; D001059:Apoproteins / Q000737:chemistry*; D002417:Cattle; D045304:Cytochromes c / Q000737:chemistry*; D003903:Deuterium; D005740:Gases; D006736:Horses; D006859:Hydrogen; D006863:Hydrogen-Ion Concentration; D007477:Ions; D007782:Lactoglobulins / Q000737:chemistry*; D009211:Myoglobin / Q000737:chemistry*; D011487:Protein Conformation; D011489:Protein Denaturation; D012996:Solutions; D021241:Spectrometry, Mass, Electrospray Ionization; D025801:Ubiquitin / Q000737:chemistry*
chemical_list: D001059:Apoproteins; D005740:Gases; D007477:Ions; D007782:Lactoglobulins; D009211:Myoglobin; D012996:Solutions; D025801:Ubiquitin; C010857:apomyoglobin; D006859:Hydrogen; D045304:Cytochromes c; D003903:Deuterium