Tuning oxidative modification by a strong electric field using nanoESI of highly conductive solutions near the minimum flow rate

Han, Zhongbao; Omata, Nozomu; Matsuda, Takeshi; Hishida, Shoki; Shuuhei, Takiguchi; Komori, Ryoki; Suzuki, Riku; Chen, Lee Chuin

doi:10.1039/d2sc07113d

Cited by 7 publications

(21 citation statements)

References 39 publications

(77 reference statements)

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“…An intriguing feature of the voltage-driven electrospray is that if the electrical conductivity is constant and known in advance, the flow rate can be precisely controlled by the emitter voltage using the spray current as the flow rate indicator. , The scanning of voltage has been applied previously to acquire the response of ionization at a nano flow rate and to trigger the oxidation caused by the strong electric field around the Taylor cone . Here, it was demonstrated that the electrospray flow rate could be programmed to follow an arbitrary pattern.…”

Section: Resultsmentioning

confidence: 99%

Feedback Control of Electrospray with and without an External Liquid Pump Using the Spray Current and the Apex Angle of a Taylor Cone for ESI-MS

et al. 2023

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An electrospray operated in the steady cone-jet mode is highly stable but the operating state can shift to pulsation or multijet modes owing to changes in flow rate, surface tension, and electrostatic variables. Here, a simple feedback control system was developed using the spray current and the apex angle of a Taylor cone to determine the error signal for correcting the emitter voltage. The system was applied to lock the cone-jet mode operation against external perturbations. For a pump-driven electrospray at a regulated flow rate, the apex angle of the Taylor cone decreased with increasing voltage. In contrast, for a voltage-driven electrospray with low flow resistance, the angle was found to increase with the emitter voltage. A simple algorithm based on iterative learning control was formulated and implemented using a personal computer to automatically correct the emitter voltage in response to the error signal. For voltage-driven electrospray ionization (ESI), the feedback control of the spray current can also be used to regulate the flow rate to an arbitrary value or pattern. Electrospray ionization-mass spectrometry (ESI-MS) with feedback control was demonstrated to produce ion signal acquisition with long-term stability that was insusceptible to the emulated external disturbances.

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Section: Resultsmentioning

confidence: 99%

Feedback Control of Electrospray with and without an External Liquid Pump Using the Spray Current and the Apex Angle of a Taylor Cone for ESI-MS

et al. 2023

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“…It is noted that for highly conductive solutions, the ion signal and CSD showed an anomalous response at an ultralow flow rate when the size of the initial charge droplet was on the order of <30 nm. , For example, highly charged species of proteins could be produced from the ∼ pH 7 solution when the flow rate was tuned to near its minimum value . Possible reasons include the heating effect at high spray current density and the strong electric field effect.…”

Section: Resultsmentioning

confidence: 99%

“…23,24 For example, highly charged species of proteins could be produced from the ∼ pH 7 solution when the flow rate was tuned to near its minimum value. 24 Possible reasons include the heating effect at high spray current density and the strong electric field effect. The flow rate effect on the average charge state for pH 2 and pH 1 solutions is shown in Figure S18.…”

Section: ■ Introductionmentioning

confidence: 99%

“…Recently, HP-nanoESI of the highly conductive aqueous solution has also been performed using commercial pipet tips as the emitter, eliminating the problems of clogging, interaction with the emitter inner surface, and the tip-to-tip reproducibility faced by the conventional pulled-glass capillary emitters. In the absence of discharge, the droplet size and the flow rate of a voltage-controlled ESI can also be accurately tuned using spray current as the reference signal to manipulate the ionization species …”

Section: Introductionmentioning

confidence: 99%

“…In the absence of discharge, the droplet size and the flow rate of a voltagecontrolled ESI can also be accurately tuned using spray current as the reference signal to manipulate the ionization species. 24 ■ EXPERIMENTAL SECTION Electrospray Ion Source. The schematic of the HP-ESI source is shown in Figure 1.…”

Section: ■ Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Probing Acid-Induced Compaction of Denatured Proteins by High-Pressure Electrospray Mass Spectrometry

Han,

Omata,

Chen

2023

Anal. Chem.

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Further increase in the acidity in the most denaturing acidic solution is known to induce compaction of the fully unfolded protein into a compact molten globule. The phenomenon of “acid-induced folding of proteins” takes place at pH ∼1 in strong acid aqueous solutions with high electrical conductivity and surface tension, a condition that is difficult to handle using conventional electrospray ionization methods for mass spectrometry. Here, high-pressure electrospray ionization (HP-ESI) is used to produce well-resolved mass spectra for proteins in strong acids with pH as low as 1. The compaction of protein conformation is indicated by a large shift in the charge state from high charges to native-like low charges. The addition of salt to the protein in the most denaturing condition also reproduces the compaction effect, thereby supporting the role of anions in this phenomenon. Similar compaction of proteins is also observed in organic solvent/acid mixtures. The charge state of the compacted protein depends on the type of anions that formed ion pairs with a positive charge on the protein. The dissociation of ion pairs during the ionization process forms neutral acids that can be observed by HP-ESI using a soft ion introduction configuration.

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Spontaneous Oxidation in Aqueous Microdroplets: Water Radical Cation as Primary Oxidizing Agent

Qiu,

Cooks

2024

Angewandte Chemie

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Exploration of the unique chemical properties of interfaces can unlock new understanding. A striking example is the finding of accelerated reactions, particularly spontaneous oxidation reactions, that occur without assistance of catalysts or external oxidants at the air interface of both aqueous and organic solutions (provided they contain some water). This finding opened a new area of interfacial chemistry but also caused heated debate regarding the primary chemical species responsible for the observed oxidation. An overview of the literature covering oxidation in microdroplets with air interfaces is provided, together with a critical examination of previous findings and hypotheses. The water radical cation/radical anion pair, formed spontaneously and responsible for the electric field at or near the droplet/air interface, is suggested to constitute the primary redox species. Mechanisms of accelerated microdroplet reactions are critically discussed and it is shown that hydroxyl radical/hydrogen peroxide formation in microdroplets does not require that these species be the primary oxidant. Instead, we suggest that hydroxyl radical and hydrogen peroxide are the products of water radical cation decay in water. The importance of microdroplet chemistry in the prebiotic environment is sketched briefly and the role of partial solvation in reaction acceleration is noted.

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Tuning oxidative modification by a strong electric field using nanoESI of highly conductive solutions near the minimum flow rate

Abstract: On-demand tunable oxidation is performed during the nanoESI-MS analysis by varying the nanoflow rate and the initial droplet size. The oxidation is initiated when the electric field of the droplet reaches ∼1.3 V nm−1.

Cited by 7 publications

References 39 publications

Feedback Control of Electrospray with and without an External Liquid Pump Using the Spray Current and the Apex Angle of a Taylor Cone for ESI-MS

Feedback Control of Electrospray with and without an External Liquid Pump Using the Spray Current and the Apex Angle of a Taylor Cone for ESI-MS

Probing Acid-Induced Compaction of Denatured Proteins by High-Pressure Electrospray Mass Spectrometry

Spontaneous Oxidation in Aqueous Microdroplets: Water Radical Cation as Primary Oxidizing Agent

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