title: Soft supercharging of biomolecular ions in electrospray ionization mass spectrometry.
abstract: The charge states of biomolecular ions in ESI-MS can be significantly increased by the addition of low-vapor supercharging (SC) reagents into the spraying solution. Despite the considerable interest from the community, the mechanistic aspects of SC are not well understood and are hotly debated. Arguments that denaturation accounts for the increased charging observed in proteins sprayed from aqueous solutions containing SC reagent have been published widely, but often with incomplete or ambiguous supporting data. In this work, we explored ESI MS charging and SC behavior of several biopolymers including proteins and DNA oligonucleotides. Analytes were ionized from 100 mM ammonium acetate (NH4Ac) aqueous buffer in both positive (ESI+) and negative (ESI-) ion modes. SC was induced either with m-NBA or by the elevated temperature of ESI capillary. For all the analytes studied we, found striking differences in the ESI MS response to these two modes of activation. The data suggest that activation with m-NBA results in more extensive analyte charging with lower degree of denaturation. When working solution with m-NBA was analyzed at elevated temperatures, the SC effect from m-NBA was neutralized. Instead, the net SC effect was similar to the SC effect achieved by thermal activation only. Overall, our observations indicate that SC reagents enhance ESI charging of biomolecules via distinctly different mechanism compared with the traditional approaches based on analyte denaturation. Instead, the data support the hypothesis that the SC phenomenon involves a direct interaction between a biopolymer and SC reagent occurring in evaporating ESI droplets.
authors.affiliation: Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China Institute of Technology, Nanchang, Jiangxi Province, 330013, China, chingin.k@gmail.com.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Chingin
authors.forename: Ning
authors.initials: N
authors.lastname: Xu
authors.forename: Huanwen
authors.initials: H
authors.lastname: Chen
mesh_terms: D001704:Biopolymers / Q000032:analysis / Q000737:chemistry*; D004247:DNA / Q000032:analysis / Q000737:chemistry; D011506:Proteins / Q000032:analysis / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*
chemical_list: D001704:Biopolymers; D011506:Proteins; D004247:DNA
references.citation: Anal Bioanal Chem. 2004 Feb;378(4):1112-23
references.pmid: 14663547
references.citation: J Phys Chem A. 2010 Jan 28;114(3):1411-9
references.pmid: 19848399
references.citation: J Am Soc Mass Spectrom. 2011 Jul;22(7):1178-86
references.pmid: 21953100
references.citation: Phys Chem Chem Phys. 2010 Nov 7;12(41):13476-83
references.pmid: 20877871
references.citation: Anal Chem. 2013 Jul 2;85(13):6469-76
references.pmid: 23724896
references.citation: Rapid Commun Mass Spectrom. 1991 Mar;5(3):101-5
references.pmid: 1666527
references.citation: J Am Chem Soc. 2003 Feb 26;125(8):2319-27
references.pmid: 12590562
references.citation: Anal Chem. 2013 Jan 2;85(1):138-46
references.pmid: 23194134
references.citation: J Am Soc Mass Spectrom. 2009 Oct;20(10):1933-43
references.pmid: 19682923
references.citation: Proc Natl Acad Sci U S A. 1998 Jun 23;95(13):7391-5
references.pmid: 9636159
references.citation: J Am Soc Mass Spectrom. 2010 Jan;21(1):127-31
references.pmid: 19854660
references.citation: J Am Soc Mass Spectrom. 1998 Dec;9(12):1248-54
references.pmid: 9835071
references.citation: J Am Soc Mass Spectrom. 2010 Jul;21(7):1144-50
references.pmid: 20356762
references.citation: J Am Soc Mass Spectrom. 2010 Oct;21(10):1762-74
references.pmid: 20673639
references.citation: J Am Soc Mass Spectrom. 2009 Apr;20(4):593-6
references.pmid: 19101165
references.citation: Anal Chem. 2012 Jun 5;84(11):4647-51
references.pmid: 22571167
references.citation: Annu Rev Biochem. 2007;76:167-93
references.pmid: 17328674
references.citation: Anal Chem. 2001 Apr 1;73(7):1455-60
references.pmid: 11321294
references.citation: Science. 2011 Oct 21;334(6054):380-385
references.pmid: 22021858
references.citation: Anal Chem. 2013 Jan 2;85(1):2-9
references.pmid: 23134552
references.citation: Biochemistry. 1972 May 9;11(10):1836-41
references.pmid: 5063536
references.citation: J Am Soc Mass Spectrom. 2012 Feb;23(2):191-200
references.pmid: 22161509
references.citation: Photochem Photobiol Sci. 2006 Jun;5(6):621-8
references.pmid: 16761091
references.citation: Anal Chem. 2012 Apr 17;84(8):3795-801
references.pmid: 22409200
references.citation: J Mass Spectrom. 2014 Jan;49(1):103-7
references.pmid: 24446269
references.citation: Nat Methods. 2008 Nov;5(11):927-33
references.pmid: 18974734
references.citation: Anal Chem. 2010 Nov 1;82(21):9050-7
references.pmid: 20942406
references.citation: Angew Chem Int Ed Engl. 2008;47(33):6247-51
references.pmid: 18642251
references.citation: Phys Chem Chem Phys. 2011 Nov 7;13(41):18288-96
references.pmid: 21399817
references.citation: J Am Soc Mass Spectrom. 1994 Jul;5(7):614-22
references.pmid: 24221963
references.citation: J Am Soc Mass Spectrom. 2012 Mar;23(3):489-97
references.pmid: 22219044
references.citation: J Am Soc Mass Spectrom. 2013 Dec;24(12):1988-96
references.pmid: 24030289