title: Gas-phase ions of human hemoglobin A, F, and S.
abstract: Hemoglobin (Hb) (α(2)β(2)) is a tetrameric protein-protein complex. Collision cross sections, hydrogen exchange levels, and tandem mass spectrometry have been used to investigate the properties of gas-phase monomer, dimer, and tetramer ions of adult human hemoglobin (Hb A, α(2)β(2)), and two variant hemoglobins: fetal hemoglobin (Hb F, α(2)γ(2)) and sickle hemoglobin (Hb S, α(2)β(2), E6V[β]). All three proteins give similar mass spectra. Monomers of Hb S and Hb F have similar cross sections, ca. 10% greater than those of Hb A. Cross sections of dimer ions of Hb S are 11% greater than those of Hb A and 6% greater than those of Hb F. Tetramers of Hb S are 13% larger than tetramers of Hb A or Hb F. Monomers and dimers of all three Hb have similar hydrogen-deuterium exchange (HDX) levels. Tetramers of Hb S exchange 16% more hydrogens than Hb A and Hb F. In tandem mass spectrometry, monomers of Hb S and Hb F require ca. 10% greater internal energy for heme loss than Hb A. Dimers (+11) of Hb A and Hb S dissociate to monomers with asymmetrical charge division; dimers of Hb F (+11) dissociate with nearly equal charge division. Tetramer ions dissociate to monomers and trimers, unlike solution Hb, which dissociates to dimers. The most stable dimers are from Hb S; the most stable tetramers from Hb F. The results with Hb S show that a single mutation in the β chain can change the physical properties of this gas-phase protein-protein complex.
authors.affiliation: Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC, V6T 1Z1, Canada.
authors.forename: Yang
authors.initials: Y
authors.lastname: Kang
authors.forename: D J
authors.initials: DJ
authors.lastname: Douglas
mesh_terms: D041961:Deuterium Exchange Measurement / Q000379:methods*; D005740:Gases / Q000737:chemistry*; D006454:Hemoglobins / Q000737:chemistry*; D006801:Humans; D008970:Molecular Weight; D046912:Multiprotein Complexes / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry / Q000379:methods*; D013816:Thermodynamics
chemical_list: D005740:Gases; D006454:Hemoglobins; D046912:Multiprotein Complexes