title: Traveling-wave Ion Mobility-Mass Spectrometry Reveals Additional Mechanistic Details in the Stabilization of Protein Complex Ions through Tuned Salt Additives.
abstract: Ion mobility-mass spectrometry is often applied to the structural elucidation of multiprotein assemblies in cases where X-ray crystallography or NMR experiments have proved challenging. Such applications are growing steadily as we continue to probe regions of the proteome that are less-accessible to such high-resolution structural biology tools. Since ion mobility measures protein structure in the absence of bulk solvent, strategies designed to more-broadly stabilize native-like protein structures in the gas-phase would greatly enable the application of such measurements to challenging structural targets. Recently, we have begun investigating the ability of salt-based solution additives that remain bound to protein ions in the gas-phase to stabilize native-like protein structures. These experiments, which utilize collision induced unfolding and collision induced dissociation in a tandem mass spectrometry mode to measure protein stability, seek to develop a rank-order similar to the Hofmeister series that categorizes the general ability of different anions and cations to stabilize gas-phase protein structure. Here, we study magnesium chloride as a potential stabilizing additive for protein structuresin vacuo, and find that the addition of this salt to solutions prior to nano-electrospray ionization dramatically enhances multiprotein complex structural stability in the gas-phase. Based on these experiments, we also refine the physical mechanism of cation-based protein complex ion stabilization by tracking the unfolding transitions experienced by cation-bound complexes. Upon comparison with unbound proteins, we find strong evidence that stabilizing cations act to tether protein complex structure. We conclude by putting the results reported here in context, and by projecting the future applications of this method.
authors.affiliation: University of Michigan, Department of Chemistry, 930 N. University Ave., Ann Arbor, MI, 48108.
authors.forename: Linjie
authors.initials: L
authors.lastname: Han
authors.forename: Brandon T
authors.initials: BT
authors.lastname: Ruotolo
keywords: Ion mobility-mass spectrometry; collision induced dissociation; collision induced unfolding; multiprotein complex; structural stabilization
references.citation: J Am Soc Mass Spectrom. 2005 Sep;16(9):1493-1497
references.pmid: 16019223
references.citation: Mass Spectrom Rev. 2004 Sep-Oct;23(5):368-89
references.pmid: 15264235
references.citation: Anal Chem. 2010 Jun 15;82(12):5363-72
references.pmid: 20481443
references.citation: J Am Chem Soc. 2011 Jul 27;133(29):11358-67
references.pmid: 21675748
references.citation: Chem Rev. 2007 Aug;107(8):3544-67
references.pmid: 17649985
references.citation: Nature. 2007 Dec 13;450(7172):973-82
references.pmid: 18075576
references.citation: Proc Natl Acad Sci U S A. 2008 Nov 25;105(47):18145-52
references.pmid: 19033474
references.citation: Chem Soc Rev. 2010 May;39(5):1633-55
references.pmid: 20419213
references.citation: J Am Soc Mass Spectrom. 2009 Apr;20(4):625-31
references.pmid: 19110442
references.citation: Structure. 2009 Sep 9;17(9):1235-43
references.pmid: 19748344
references.citation: Rapid Commun Mass Spectrom. 2008 Oct;22(20):3297-304
references.pmid: 18816489
references.citation: J Am Chem Soc. 2006 Sep 6;128(35):11433-42
references.pmid: 16939266
references.citation: Analyst. 2011 Sep 7;136(17):3534-41
references.pmid: 21445388
references.citation: Anal Chem. 2007 Jan 15;79(2):416-25
references.pmid: 17222003
references.citation: J Am Soc Mass Spectrom. 2009 Mar;20(3):341-8
references.pmid: 19110440
references.citation: PLoS One. 2009 Sep 28;4(9):e7202
references.pmid: 19784376
references.citation: Nat Rev Mol Cell Biol. 2006 Dec;7(12):909-18
references.pmid: 17139331
references.citation: Rapid Commun Mass Spectrom. 2010 Oct 30;24(20):3033-3042
references.pmid: 20872636
references.citation: Annu Rev Phys Chem. 2007;58:511-33
references.pmid: 17129173
references.citation: Chem Biol. 2009 Apr 24;16(4):382-90
references.pmid: 19389624
references.citation: Proc Natl Acad Sci U S A. 2010 Oct 5;107(40):17146-51
references.pmid: 20855577
references.citation: Nat Rev Mol Cell Biol. 2002 Sep;3(9):639-50
references.pmid: 12209124
references.citation: J Struct Biol. 2008 Sep;163(3):186-95
references.pmid: 18602011
references.citation: Anal Chem. 2009 Sep 15;81(18):7801-6
references.pmid: 19746998
references.citation: Annu Rev Biochem. 2007;76:167-93
references.pmid: 17328674
references.citation: Nat Protoc. 2007;2(3):715-26
references.pmid: 17406634
references.citation: Science. 2011 Oct 21;334(6054):380-385
references.pmid: 22021858
references.citation: Angew Chem Int Ed Engl. 2012 Jun 4;51(23):5692-5
references.pmid: 22529039
references.citation: Science. 2005 Dec 9;310(5754):1658-61
references.pmid: 16293722
references.citation: Proc Natl Acad Sci U S A. 2003 Sep 16;100(19):10611-6
references.pmid: 12947045
references.citation: Expert Rev Proteomics. 2012;9(1):47-58
references.pmid: 22292823
references.citation: EMBO Rep. 2006 Jun;7(6):605-10
references.pmid: 16729021
references.citation: Proc Natl Acad Sci U S A. 2008 Nov 25;105(47):18139-44
references.pmid: 18599441
references.citation: Curr Opin Struct Biol. 2011 Oct;21(5):641-9
references.pmid: 21880480
references.citation: J Am Soc Mass Spectrom. 2009 Oct;20(10):1851-8
references.pmid: 19643633
references.citation: Analyst. 2011 Jan 7;136(1):20-8
references.pmid: 20820495
references.citation: Proteomics. 2012 May;12(10):1547-64
references.pmid: 22611037
references.citation: J Am Soc Mass Spectrom. 2007 Jul;18(7):1206-16
references.pmid: 17434746
references.citation: Clin Chem. 2003 Jul;49(7):1041-4
references.pmid: 12816898
references.citation: Proc Natl Acad Sci U S A. 2010 Apr 13;107(15):6794-8
references.pmid: 20351246
references.citation: Curr Opin Chem Biol. 2006 Oct;10(5):402-8
references.pmid: 16935553
references.citation: PLoS One. 2010 Aug 10;5(8):e12080
references.pmid: 20711472
references.citation: Nat Methods. 2008 Nov;5(11):927-33
references.pmid: 18974734
references.citation: Nature. 2003 Mar 13;422(6928):216-25
references.pmid: 12634795
references.citation: J Am Chem Soc. 2003 Mar 5;125(9):2817-26
references.pmid: 12603172
references.citation: J Am Soc Mass Spectrom. 2011 Nov;22(11):1978-90
references.pmid: 21952780
references.citation: Acc Chem Res. 2010 Aug 17;43(8):1072-9
references.pmid: 20557067
references.citation: Faraday Discuss. 2013;160:371-88; discussion 389-403
references.pmid: 23795511
references.citation: Nat Methods. 2009 Aug;6(8):585-7
references.pmid: 19578383
references.citation: Rapid Commun Mass Spectrom. 2011 Jun 15;25(11):1559-66
references.pmid: 21594930
references.citation: Rapid Commun Mass Spectrom. 2004;18(20):2401-14
references.pmid: 15386629
references.citation: J Phys Chem B. 2011 Apr 7;115(13):3614-21
references.pmid: 21395304
references.citation: Angew Chem Int Ed Engl. 2010 Dec 3;49(49):9448-51
references.pmid: 21031381
references.citation: Anal Chem. 2010 Nov 15;82(22):9557-65
references.pmid: 20979392
references.citation: Annu Rev Anal Chem (Palo Alto Calif). 2008;1:293-327
references.pmid: 20636082
references.citation: Nat Protoc. 2008;3(7):1139-52
references.pmid: 18600219