An Isotope-Induced Polarity Bias in Electrospray Ionization Mass Spectrometry.
8 affiliations
- 1Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Solna 171 65, Sweden.
- 2Center for Sustainable Materials (SusMat), School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
- 3Department of Medical Biochemistry and Microbiology & Science for Life Laboratory & Center of Excellence for the Chemical Mechanisms of Life, Uppsala University, Uppsala Biomedical Centre, Uppsala 752 37, Sweden.
- 4Department of Medical Biochemistry and Biophysics, Karolinska Institutet, Stockholm 171 65, Sweden.
- 5Department for Cell and Molecular Biology, Uppsala University, Uppsala 751 24, Sweden.
- 6Institute of Chemistry and Biochemistry, Freie Universität Berlin, Berlin 14195, Germany.
- 7Department of Molecular Physics, Fritz Haber Institute of the Max Planck Society, Berlin 14195, Germany.
- 8Department of Chemistry for Life Sciences, Uppsala University, Uppsala 751 23, Sweden.
Abstract
Heavy water (D₂O) is commonly used as a solvent additive in electrospray ionization-mass spectrometry (ESI-MS) to probe biomolecular interactions under the assumption that isotopic substitution does not significantly affect the ionization process. However, D₂O differs measurably from H₂O in several physicochemical properties, which can influence ionization across biomolecular classes. Here, we systematically investigate how D₂O influences native ESI across biomolecular classes and show that D₂O introduces a pronounced, polarity-dependent detection bias which can suppress the signal of proteins and peptides in negative ion mode relative to other classes of biomolecules. Protein signal suppression is mitigated by reducing primary ESI droplet size or adding volatile ammonium salts, implicating altered droplet evolution and salt retention in D₂O. Its magnitude is strongly dependent on analyte acidity: basic and moderately acidic proteins are most affected, whereas extremely negatively charged proteins, RNA, and polysaccharides remain largely unaffected. Signal loss also correlates with extensive sodium adduction and peak splitting rather than impaired charging. Exploiting this selectivity, we demonstrate controlled switching between peptide and RNA detection in a coacervate-based cellular delivery system. These findings reveal an unexpected solvent-dependent bias in negative-mode native MS measurements which can be exploited for experimental design.
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BibTeX
@article{neo2026isotopeinduced,
title = {{An Isotope-Induced Polarity Bias in Electrospray Ionization Mass Spectrometry.}},
author = {Qi Ying Neo and Henry T P Annecke and Irena Papageorgiou and Axel Leppert and Katja Petzold and Kevin Pagel and Ali Miserez and Erik G Marklund and Nicklas Österlund and Michael Landreh},
journal = {ACS measurement science au},
year = {2026},
month = jul,
doi = {10.1021/acsmeasuresciau.6c00134},
url = {https://europepmc.org/article/MED/42921452},
note = {CC BY},
}
RIS
TY - JOUR
TI - An Isotope-Induced Polarity Bias in Electrospray Ionization Mass Spectrometry.
AU - Qi Ying Neo
AU - Henry T P Annecke
AU - Irena Papageorgiou
AU - Axel Leppert
AU - Katja Petzold
AU - Kevin Pagel
AU - Ali Miserez
AU - Erik G Marklund
AU - Nicklas Österlund
AU - Michael Landreh
PY - 2026
DA - 2026/07/14
JO - ACS measurement science au
DO - 10.1021/acsmeasuresciau.6c00134
UR - https://europepmc.org/article/MED/42921452
AB - Heavy water (D₂O) is commonly used as a solvent additive in electrospray ionization-mass spectrometry (ESI-MS) to probe biomolecular interactions under the assumption that isotopic substitution does not significantly affect the ionization process. However, D₂O differs measurably from H₂O in several physicochemical properties, which can influence ionization across biomolecular classes. Here, we systematically investigate how D₂O influences native ESI across biomolecular classes and show that D₂O introduces a pronounced, polarity-dependent detection bias which can suppress the signal of proteins and peptides in negative ion mode relative to other classes of biomolecules. Protein signal suppression is mitigated by reducing primary ESI droplet size or adding volatile ammonium salts, implicating altered droplet evolution and salt retention in D₂O. Its magnitude is strongly dependent on analyte acidity: basic and moderately acidic proteins are most affected, whereas extremely negatively charged proteins, RNA, and polysaccharides remain largely unaffected. Signal loss also correlates with extensive sodium adduction and peak splitting rather than impaired charging. Exploiting this selectivity, we demonstrate controlled switching between peptide and RNA detection in a coacervate-based cellular delivery system. These findings reveal an unexpected solvent-dependent bias in negative-mode native MS measurements which can be exploited for experimental design.
SN - 2694-250X
ER -