Supercharging protein ions in native mass spectrometry using theta capillary nanoelectrospray ionization mass spectrometry and cyclic alkylcarbonates

Wang, Huixin; Brown, Sheri; Lee, Hyun Eui; Zenaidee, Muhammad A.; Supuran, Claudiu T.; Donald, William A.

doi:10.1016/j.aca.2017.11.075

Cited by 21 publications

(35 citation statements)

References 90 publications

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“…Similar results were obtained for myoglobin (Figure 2b, e) and carbonic anhydrase II (Figure 2c, f). In a previous report 25 in which θ-nanoESI was used for native protein supercharging, protein ion charge states were higher than those observed here. For example, the average charge state reported for cytochrome c was 23.1 ± 0.1 compared to 19.1 ± 0.6 in Figure 2d.…”

Section: Resultscontrasting

confidence: 75%

“…Native supercharging methods include: (i) doping small molecule additives with low vapor pressure directly into native protein solutions in low concentrations (e.g., m-nitrobenzyl alcohol [16][17][18][19][20] or sulfolane 17,21,22 ), (ii) increasing the electric field between the ESI emitter and the MS entrance ("electrothermal supercharging"), 23 and (iii) dual channel ESI using theta capillaries for rapid mixing of the native and denaturing solutions during the ESI process. 24,25 For the latter method, the extent of protein ion charging can be increased by more than 100% compared to the alternative methods for common test proteins. Theta capillaries are nanoelectrospray ionization (nanoESI) emitters that are divided into two channels by a glass septum 26,27 which can be used to rapidly mix two solutions during ESI prior to MS analysis (Figure 1a, b).…”

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confidence: 99%

“…27 In native supercharging via θ-nanoESI, one channel of the theta capillary is loaded with a native protein solution (in ammonium acetate) and the other channel can be loaded with a denaturing solution containing a supercharging agent, such as a cyclic alkyl carbonate supercharging additive (e.g., 4-vinyl-1,3-dioxolan-2-one or 1,2-butylene carbonate). 25 The mixing of the two solutions during the ESI process can result in the formation of protein ions in comparable charge states as those formed directly from a denaturing supercharging solution. The rapid timescale of mixing and high protein ion charge states that can be formed should be particularly useful for probing solution-phase structure by hydrogen-deuterium exchange MS. 12 However, the mechanism of solution mixing in θ-nanoESI has been the subject of some controversy in the literature.…”

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confidence: 99%

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On the mechanism of theta capillary nanoelectrospray ionization for the formation of highly charged protein ions directly from native solutions

Brown

Zenaidee

Loo

et al. 2022

Preprint

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Theta capillary nanoelectrospray ionization (θ-nanoESI) can be used to ‘supercharge’ protein ions directly from solution for detection by mass spectrometry (MS). In native top-down MS, the extent of protein charging is low. Given that ions with more charge fragment more readily, increasing charge can enhance the extent of sequence information obtained by top-down MS. For θ-nanoESI, dual-channelled nanoESI emitters are used to mix two solutions in low to sub-μs prior to MS. The mechanism for θ-nanoESI mixing has been reported to occur in the Taylor cone prior to ESI-droplet formation, or by the fusion of droplets formed from separate Taylor cones. Using θ-nanoESI-ion mobility-MS, native protein solutions were rapidly mixed with denaturing supercharging solutions to form protein ions in significantly higher charge states and with more elongated structures than those formed by pre-mixing the solutions prior to nanoESI-MS. If θ-nanoESI mixing occurred in the Taylor cone, then the extent of protein charging and unfolding should be comparable or less than that obtained by pre-mixing solutions. Thus, these data are consistent with mixing occurring via droplet fusion rather than in the Taylor cone prior to ESI droplet formation. The presence of supercharging additives in pre-mixed solutions can suppress volatile electrolyte evaporation, limiting the extent of protein charging compared to when the additive is delivered via one channel of a θ-nanoESI emitter. In θ-nanoESI, the formation of two Taylor cones can presumably result in substantial electrolyte evaporation from the ESI droplets containing native-like proteins prior to droplet fusion, thereby enhancing ion charging.

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Section: Resultscontrasting

confidence: 75%

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confidence: 99%

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confidence: 99%

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On the mechanism of theta capillary nanoelectrospray ionization for the formation of highly charged protein ions directly from native solutions

Brown

Zenaidee

Loo

et al. 2022

Preprint

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“…Numerous studies have found that more highly charged ions are generated by the addition of small organic molecules to the biomolecule solutions undergoing ESI. This process is known as “supercharging.” Some studies suggest that supercharging is the result of denaturation; the organic reagents induce the unfolding of a molecule (ie, conformational change) and changes in droplet surface tension . Other studies suggest that supercharging is due to a direct interaction between biomolecules and supercharging reagents .…”

Section: Introductionmentioning

confidence: 99%

“…This process is known as "supercharging." [32][33][34][35][36][37][38][39][40][41][42][43][44][45] Some studies suggest that supercharging is the result of denaturation; the organic reagents induce the unfolding of a molecule (ie, conformational change) and changes in droplet surface tension. [46][47][48][49][50][51] Other studies suggest that supercharging is due to a direct interaction between biomolecules and supercharging reagents.…”

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confidence: 99%

The use of chromium(III) complexes to enhance peptide protonation by electrospray ionization mass spectrometry

et al. 2018

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The addition of trivalent chromium, Cr(III), reagents to peptide solutions can increase the intensity of doubly protonated peptides, [M + 2H]2+, through electrospray ionization (ESI). Three model heptapeptides were studied: neutral (AAAAAAA), acidic (AAEEEAA), and basic (AAAKAAA). The neutral and acidic peptides form almost no 2+ ions in the absence of Cr(III). Twenty Cr(III) complexes were used as potential enhanced protonation reagents, including 11 complexes with nonlabile ligands and nine with labile ligands. The complexes that provide the most abundant [M + 2H]2+, the greatest [M + 2H]2+ to [M + H]+ ratio, and the cleanest mass spectra are [Cr(H2O)6](NO3)3·3H2O and [Cr(THF)3]Cl3. Anions in Cr(III) reagents can also affect the intensity of [M + 2H]2+ and the [M + 2H]2+ to [M + H]+ ratio through cation‐anion interactions. The influence of anions on the extent of peptide protonation follows the trend ClO4− ˃ SO42− ˃ Br− ˃ Cl− ˃ F− ≈ NO3−. Solvent effects and complexes with varying number of water ligands were investigated to study the importance of water in enhanced protonation. Aqueous solvent systems and Cr(III) complexes that have at least one bound water ligand in solution must be used for successful increase in the intensity of [M + 2H]2+, which indicates that water is involved in the mechanism of Cr(III)‐induced enhanced protonation. The ESI source design is also important because no enhanced protonation was observed using a Z‐spray source. The current results suggest that this Cr(III)‐induced effect occurs during the ESI desolvation process.

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Distinguishing Protein Chemical Topologies Using Supercharging Ion Mobility Spectrometry‐Mass Spectrometry

Lee,

Im,

Liu

et al. 2023

Angewandte Chemie

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A technique combining ion mobility spectrometry‐mass spectrometry (IMS‐MS) and supercharging electrospray ionization (ESI) has been demonstrated to differentiate protein chemical topology effectively. Incorporating as many charges as possible into proteins via supercharging ESI allows the protein chains to be largely unfolded and stretched, revealing their hidden chemical topology. Different chemical topologies result in differing geometrical sizes of the unfolded proteins due to constraints in torsional rotations in cyclic domains. By introducing new topological indices, such as the chain‐length‐normalized collision cross‐section (CCS) and the maximum charge state (zM) in the extensively unfolded state, we were able to successfully differentiate various protein chemical topologies, including linear chains, ring‐containing topologies (lasso, tadpole, multicyclics, etc.), and mechanically interlocked rings, like catenanes.

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Supercharging protein ions in native mass spectrometry using theta capillary nanoelectrospray ionization mass spectrometry and cyclic alkylcarbonates

Cited by 21 publications

References 90 publications

On the mechanism of theta capillary nanoelectrospray ionization for the formation of highly charged protein ions directly from native solutions

On the mechanism of theta capillary nanoelectrospray ionization for the formation of highly charged protein ions directly from native solutions

The use of chromium(III) complexes to enhance peptide protonation by electrospray ionization mass spectrometry

Distinguishing Protein Chemical Topologies Using Supercharging Ion Mobility Spectrometry‐Mass Spectrometry

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