title: Hydrogen/deuterium exchange of myoglobin ions in a linear quadrupole ion trap.
abstract: The hydrogen/deuterium (H/D) exchange of gas-phase ions of holo- and apo-myoglobin has been studied by confining the ions in a linear quadrupole ion trap with D(2)O or CD(3)OD at a pressure of several mTorr. Apo-myoglobin ions were formed by collision-induced dissociation of holo-myoglobin ions between the orifice and skimmer of the ion sampling system. The exchange takes place on a time scale of seconds. Earlier cross section measurements have shown that holo-myoglobin ions can have more compact structures than apo-myoglobin. Despite this, both holo-myoglobin and apo-myoglobin in charge states +8 to +14 are found to exchange nearly the same number of hydrogens (ca. 103) in 4 s. It is possible the ions fold or unfold to new conformations on the much longer time scale of the exchange experiment compared with the cross section measurements.
mesh_terms: D001059:Apoproteins / Q000737:chemistry; D003903:Deuterium; D017666:Deuterium Oxide; D004563:Electrochemistry; D006801:Humans; D006859:Hydrogen; D006863:Hydrogen-Ion Concentration; D007474:Ion Exchange; D013058:Mass Spectrometry; D009211:Myoglobin / Q000737:chemistry*
chemical_list: D001059:Apoproteins; D009211:Myoglobin; C010857:apomyoglobin; D006859:Hydrogen; D003903:Deuterium; D017666:Deuterium Oxide