title: Combined ion-mobility and mass-spectrometry investigations of metallothionein complexes using a tandem mass spectrometer with a segmented second quadrupole.
abstract: Rabbit metallothionein (MT) 2A complexes with Cd(II), Zn(II), Ag(I), Cu(I), Hg(II), arsenite, monomethylarsonous acid (MMA), and dimethylarsinous acid (DMA) have been examined using ion-mobility measurements and mass spectrometry in a triple-quadrupole mass spectrometer equipped with a segmented second quadrupole that doubled as an ion-mobility cell [Guo, Y.; Wang, J.; Javahery, G.; Thomson, B. A.; Siu, K. W. M. An Ion-Mobility Spectrometer with Radial Collisional Focusing. Anal. Chem.2005, 77, 266-275]. The metal ions confer conformational rigidity on the MT complexes, which counteracts Coulombic repulsion among protons added as a result of electrospray. Triply and quadruply protonated Cd(7)MT2A have smaller cross-sections than the Cd(7)MT2A structure deduced from published NMR data. For the 6+ ions, the As(6)MT2A complex has a cross-section of 790 A(2); the MMA(10)MT2A complex, 920 A(2); and the DMA(20)MT2A complex, 1220 A(2). This increase in cross-section of the As(III) species, from As(3+) to MMA to DMA, is interpreted as a consequence of decreasing multiple coordination and increasing number of methyl groups.
authors.affiliation: Department of Chemistry and Center for Research in Mass Spectrometry, York University, 4700 Keele Street, Toronto, Ontario M3J 1P3, Canada.
authors.forename: Yuzhu
authors.initials: Y
authors.lastname: Guo
authors.forename: Yun
authors.initials: Y
authors.lastname: Ling
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Thomson
authors.forename: K W Michael
authors.initials: KW
authors.lastname: Siu
mesh_terms: D000818:Animals; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008099:Liver / Q000378:metabolism*; D008668:Metallothionein / Q000032:analysis* / Q000737:chemistry*; D008670:Metals / Q000032:analysis* / Q000737:chemistry*; D011817:Rabbits; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation* / Q000379:methods; D018511:Systems Integration
chemical_list: D008670:Metals; D008668:Metallothionein