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Soft Supercharging of Biomolecular Ions in Electrospray Ionization Mass Spectrometry

  • Research Article
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Journal of The American Society for 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.

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Acknowledgments

This work was supported by the National Natural Science Fund of China (no. 21305012), Science and Technology Planning Project at the Department of Science and Technology of Jiangxi Province, China (no. 20124ACB00700), and the Jiangxi Province Program for Training Talents in Science and Technology (no. 2010DD01300).

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  1. Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China Institute of Technology, Nanchang, Jiangxi Province, 330013, China

    Konstantin Chingin, Ning Xu & Huanwen Chen

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  1. Konstantin Chingin
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  2. Ning Xu
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  3. Huanwen Chen
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Correspondence to Konstantin Chingin or Huanwen Chen.

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Chingin, K., Xu, N. & Chen, H. Soft Supercharging of Biomolecular Ions in Electrospray Ionization Mass Spectrometry. J. Am. Soc. Mass Spectrom. 25, 928–934 (2014). https://doi.org/10.1007/s13361-014-0887-y

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  • DOI: https://doi.org/10.1007/s13361-014-0887-y

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