Conducting and characterizing femto flow electrospray ionization

Li, Huishan; Allen, Nicholas; Li, Mengtian; Li, Anyin

doi:10.1039/d1an02190g

Cited by 11 publications

(18 citation statements)

References 35 publications

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“…The ultralow flow rate of <20 nL/min usually requires an offline capillary with an i.d. of several micrometers. , There was also development on ESI with submicrometer capillaries. − The mechanism behind some unique features of a nanoESI was given by Karas et al, , and there are rich literature reports on the enhanced sensitivity for peptides and proteins by lowering the flow rate of nanoESI. But by using a nanospray emitter, an opposite result was also observed, i.e.…”

Section: Introductionmentioning

confidence: 99%

A Subtle Change in Nanoflow Rate Alters the Ionization Response As Revealed by Scanning Voltage ESI-MS

Han

Chen

2022

Anal. Chem.

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The small charged droplet generated from the nanoelectrospray ionization (nanoESI) source at nL/min flow rate gives its unique feature of high-performance ionization. A continuous scan of the flow rate in this regime can trace the effect of droplet size in greater detail for a better understanding of the ionization process. To date, such practical implementation is hindered by the lack of a suitable liquid pump and the reproducibility of microcapillaries-based systems. Here, offline nanoESI mass spectrometry with a continuously varying flow rate in a dynamic range of several hundred pL/min to ∼100 nL/min was performed by the precision scanning of ESI high voltage (HV). The principle is based on the new paradigm of generating nanoelectrospray from a large Taylor cone with a known spray current–flow rate relationship. The instantaneous flow rate controlled by the HV was determined by simultaneous measurement of the spray current. The system is successfully applied to reveal the role of nanoflow rate on the average charge state of proteins, analysis of analyte mixture, and desalting effect. With the use of a buffer solution with high electric conductivity, a highly controllable oxidative modification was also observed by tuning the flow rate below a threshold of ∼5 nL/min, a finding that has potential application to on-demand oxygen labeling.

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Section: Introductionmentioning

confidence: 99%

A Subtle Change in Nanoflow Rate Alters the Ionization Response As Revealed by Scanning Voltage ESI-MS

Han

Chen

2022

Anal. Chem.

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“…One of the more attractive routes for characterizing and applying the femtoESI mode is its perceived effect on improving IE of analytes in a mixture. The perceived increase in IE is thought to be caused by the decreased droplet size of the femtoESI mode as a result of decreasing solution flow rate. ,,− ,− , Sufficiently small droplets approach the statistical likelihood that each droplet formed will contain ≤1 analyte at a bulk solution concentration of ∼10 μM, meaning that under charge residue model (CRM) conditions more of the droplet charge will be imparted on a single analyte leading to more efficient charging. To achieve these conditions, droplets formed will need to have a radius of ∼30 nm, which has been hypothesized to be of the magnitude generated by femtoESI .…”

Section: Resultsmentioning

confidence: 99%

“…The perceived increase in IE is thought to be caused by the decreased droplet size of the femtoESI mode as a result of decreasing solution flow rate. ,,− ,− , Sufficiently small droplets approach the statistical likelihood that each droplet formed will contain ≤1 analyte at a bulk solution concentration of ∼10 μM, meaning that under charge residue model (CRM) conditions more of the droplet charge will be imparted on a single analyte leading to more efficient charging. To achieve these conditions, droplets formed will need to have a radius of ∼30 nm, which has been hypothesized to be of the magnitude generated by femtoESI . Based on previous studies by Rahman et al, flow rate has a large impact on the optimal overall and charge state signal attainable for each analyte where there is an optimal flow rate for each analyte of the mixture .…”

Section: Resultsmentioning

confidence: 99%

“…To achieve these conditions, droplets formed will need to have a radius of ∼30 nm, which has been hypothesized to be of the magnitude generated by femtoESI. 2 Based on previous studies by Rahman et al, flow rate has a large impact on the optimal overall and charge state signal attainable for each analyte where there is an optimal flow rate for each analyte of the mixture. 35 To reach this level of optimization, further instrumentation development is needed for femtoESI.…”

Section: ■ Introductionmentioning

confidence: 99%

“…The ionization current associated with an electrospray ionization (ESI) emitter is one indicator of performance and the characteristics of the ESI process and yields insight into ion formation and predictions of charged droplet size . The previously reported femtomode of ESI (femtoESI) delivers a low current ion beam for analysis by mass spectrometry. − The femtoESI mode previously suffered from a narrow applied voltage range where femtoESI signals are achieved. To achieve a more facile generation of the femtoESI mode signal over a broad range of applied voltages, a circuit scheme utilizing large resistors is used.…”

Section: Introductionmentioning

confidence: 99%

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Gigaohm and Teraohm Resistors in Femtoamp and Picoamp Electrospray Ionization

Allen

Wang

et al. 2023

J. Am. Soc. Mass Spectrom.

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The femtoamp electrospray ionization (femtoESI) mode has been shown to exhibit unique characteristics that may facilitate ionization efficiency studies and experiments requiring low ion beam flux. Investigation of femtoESI was hindered by a tiny, applied voltage window of 10−100 V, beyond which ionization currents quickly jumped to nanoamps. This window was difficult to locate because the exact onset voltage fluctuates due to variations in ion source alignments. Large resistors (0.1−100 TΩ) in series effectively expanded the femtoESI applied voltage range, up to 1400 V. By swapping resistors, rapid alternation allows for the comparison of both ESI modes under the same alignment. In peptide mixtures, analytes with lower surface activity are suppressed in the nanoESI mode whereas the femtoESI mode shows signal enhancement of less surface-active species. For protein solutions, there is little change in the charge states generated but the femtoESI mode does show a decrease in the average charge state of protein peaks. Peptides and proteins analyzed in the femtoESI mode also tend to generate higher intensity sodiated peaks over protonated peaks at specific charge states compared with nanoESI mode operation.

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Native top‐down mass spectrometry for higher‐order structural characterization of proteins and complexes

Liu

Xia

2022

Mass Spectrometry Reviews

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Progress in structural biology research has led to a high demand for powerful and yet complementary analytical tools for structural characterization of proteins and protein complexes. This demand has significantly increased interest in native mass spectrometry (nMS), particularly native top‐down mass spectrometry (nTDMS) in the past decade. This review highlights recent advances in nTDMS for structural research of biological assemblies, with a particular focus on the extra multi‐layers of information enabled by TDMS. We include a short introduction of sample preparation and ionization to nMS, tandem fragmentation techniques as well as mass analyzers and software/analysis pipelines used for nTDMS. We highlight unique structural information offered by nTDMS and examples of its broad range of applications in proteins, protein‐ligand interactions (metal, cofactor/drug, DNA/RNA, and protein), therapeutic antibodies and antigen‐antibody complexes, membrane proteins, macromolecular machineries (ribosome, nucleosome, proteosome, and viruses), to endogenous protein complexes. The challenges, potential, along with perspectives of nTDMS methods for the analysis of proteins and protein assemblies in recombinant and biological samples are discussed.

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Conducting and characterizing femto flow electrospray ionization

Abstract: Femto flow electrospray ionization (ESI) ranging from 240 fL/min to low pico flow (<10 pL/min) was conducted and measured using submicron emitter tip and relay ESI configuration. Signature analyte ion...

Cited by 11 publications

References 35 publications

A Subtle Change in Nanoflow Rate Alters the Ionization Response As Revealed by Scanning Voltage ESI-MS

A Subtle Change in Nanoflow Rate Alters the Ionization Response As Revealed by Scanning Voltage ESI-MS

Gigaohm and Teraohm Resistors in Femtoamp and Picoamp Electrospray Ionization

Native top‐down mass spectrometry for higher‐order structural characterization of proteins and complexes

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