Recent trends of capillary electrophoresis‐mass spectrometry in proteomics research

In the paper

“Mass spectrometry (MS)–based methods continue to be the most widely used methods for high-throughput proteomics research1–4”

What the sources say

• Not checked yetcites [1] Zhang Y, Fonslow BR, Shan B, Baek MC, Yates JR 3rd. Protein analysis by shotgun/bottom-up proteomics. Chemical reviews. 2013; 113(4): 2343– 2394. 23438204 PMC3751594 source
• Not checked yetcites [2] Yates JR, Ruse CI, Nakorchevsky A. Proteomics by mass spectrometry: approaches, advances, and applications. Annual review of biomedical engineering. 2009; 11: 49– 79. 19400705 source
• Not checked yetcites [3] Nilsson T, Mann M, Aebersold R, Yates JR 3rd, Bairoch A, Bergeron JJ. Mass spectrometry in high-throughput proteomics: ready for the big time. Nature methods. 2010; 7(9): 681– 685. 20805795 source
• Not checked yetcites [4] Yates JR 3rd. The revolution and evolution of shotgun proteomics for large-scale proteome analysis. Journal of the American Chemical Society. 2013; 135(5): 1629– 1640. 23294060 PMC3751590 source

In the paper

“Capillary electrophoresis is a mature separation technology that is effectively coupled with mass spectrometry (CE-MS) and is well suited for this purpose7,8.”

What the sources say

• Not checked yetcites [7] Mischak H, Coon JJ, Novak J, Weissinger EM, Schanstra JP, Dominiczak AF. Capillary electrophoresis-mass spectrometry as a powerful tool in biomarker discovery and clinical diagnosis: an update of recent developments. Mass spectrometry reviews. 2009; 28(5): 703– 724. 18973238 PMC2720435 source
• Not checked yetcites [8] Belczacka I, Latosinska A, Siwy J, Urinary CE-MS peptide marker pattern for detection of solid tumors. Scientific reports. 2018; 8(1): 5227– 5227. 29588543 PMC5869723 source

In the paper

“Native MS provides a proteomics tool that enables identification and characterization of these biomolecular structures and advances the understanding of their biological pathways at the molecular level19,20,35.”

What the sources say

• Not checked yetcites [19] Li H, Nguyen HH, Ogorzalek Loo RR, Campuzano IDG, Loo JA. An integrated native mass spectrometry and top-down proteomics method that connects sequence to structure and function of macromolecular complexes. Nature chemistry. 2018; 10(2): 139– 148. PMC5784781 29359744 source
• Not checked yetcites [20] Leney AC, Heck AJ. Native Mass Spectrometry: What is in the Name? Journal of the American Society for Mass Spectrometry. 2017; 28(1): 5– 13. 27909974 PMC5174146 source
• Not checked yetcites [35] Belov AM, Viner R, Santos MR, Analysis of Proteins, Protein Complexes, and Organellar Proteomes Using Sheathless Capillary Zone Electrophoresis - Native Mass Spectrometry. Journal of the American Society for Mass Spectrometry. 2017; 28(12): 2614– 2634. 28875426 PMC5709234 source

In the paper

“Capillary isoelectric focusing (cIEF)12 is another useful, but less commonly used CE technique.”

What the sources say

• Not checked yetcites [12] Kahle J, Stein M, Watzig H. Design of experiments as a valuable tool for biopharmaceutical analysis with (imaged) capillary isoelectric focusing. Electrophoresis. 2019. 31177564 source

In the paper

“Top-down analysis can provide unique insights into a protein’s structure by providing precise molecular weight measurements, the identification of multiple PTMs5,16,28 and in-depth proteoform characterization (different forms of a single protein generated from a gene)32.”

What the sources say

• Not checked yetcites [5] Fonslow BR, Yates JR 3rd. Capillary electrophoresis applied to proteomic analysis. Journal of separation science. 2009; 32(8): 1175– 1188. 19360788 PMC3509210 source
• Not checked yetcites [16] Chen B, Brown KA, Lin Z, Ge Y. Top-Down Proteomics: Ready for Prime Time? Analytical chemistry. 2018; 90(1): 110– 127. 29161012 PMC6138622 source
• Not checked yetcites [28] Haselberg R, de Jong GJ, Somsen GW. CE-MS for the analysis of intact proteins 2010–2012. Electrophoresis. 2013; 34(1): 99– 112. 23161520 source
• Not checked yetcites [32] Smith LM, Kelleher NL. Proteoform: a single term describing protein complexity. Nature methods. 2013; 10(3): 186– 187. 23443629 PMC4114032 source

In the paper

“TDMS is an emerging approach that provides detailed structural information on intact proteins, including characterization of PTMs16.”

What the sources say

• Not checked yetcites [16] Chen B, Brown KA, Lin Z, Ge Y. Top-Down Proteomics: Ready for Prime Time? Analytical chemistry. 2018; 90(1): 110– 127. 29161012 PMC6138622 source

In the paper

“Native MS can be used to interrogate the structure of intact proteins in their near native state, with an emphasis on preserving noncovalent protein-protein and protein-ligand complexes20.”

What the sources say

• Not checked yetcites [20] Leney AC, Heck AJ. Native Mass Spectrometry: What is in the Name? Journal of the American Society for Mass Spectrometry. 2017; 28(1): 5– 13. 27909974 PMC5174146 source

In the paper

“This approach is well-known for its high-throughput performance; however, critical information about PTMs and subunit protein assemblies (via non-covalent interactions) is generally lost after proteolysis14,31.”

What the sources say

• Not checked yetcites [14] Toby TK, Fornelli L, Kelleher NL. Progress in Top-Down Proteomics and the Analysis of Proteoforms. Annual review of analytical chemistry (Palo Alto, Calif). 2016; 9(1): 499– 519. PMC5373801 27306313 source
• Not checked yetcites [31] Catherman AD, Skinner OS, Kelleher NL. Top Down proteomics: facts and perspectives. Biochemical and biophysical research communications. 2014; 445(4): 683– 693. 24556311 PMC4103433 source

In the paper

“Native MS provides information about ligand binding, dynamics, stoichiometry of individual subunits, stability, topology, and assembly structural properties35.”

What the sources say

• Not checked yetcites [35] Belov AM, Viner R, Santos MR, Analysis of Proteins, Protein Complexes, and Organellar Proteomes Using Sheathless Capillary Zone Electrophoresis - Native Mass Spectrometry. Journal of the American Society for Mass Spectrometry. 2017; 28(12): 2614– 2634. 28875426 PMC5709234 source

In the paper

“PTM patterns can provide insight into potentially significant biological processes14,16,17”

What the sources say

• Not checked yetcites [14] Toby TK, Fornelli L, Kelleher NL. Progress in Top-Down Proteomics and the Analysis of Proteoforms. Annual review of analytical chemistry (Palo Alto, Calif). 2016; 9(1): 499– 519. PMC5373801 27306313 source
• Not checked yetcites [16] Chen B, Brown KA, Lin Z, Ge Y. Top-Down Proteomics: Ready for Prime Time? Analytical chemistry. 2018; 90(1): 110– 127. 29161012 PMC6138622 source
• Not checked yetcites [17] Aebersold R, Agar JN, Amster IJ, How many human proteoforms are there? Nature chemical biology. 2018; 14(3): 206– 214. 29443976 PMC5837046 source

In the paper

“The sheathless interface has been widely used in proteomics research to provide ultrasensitive analysis56–58, although it is limited by potential blocking of the pores.”

What the sources say

• Not checked yetcites [56] Kammeijer GS, Kohler I, Jansen BC, Dopant Enriched Nitrogen Gas Combined with Sheathless Capillary Electrophoresis-Electrospray Ionization-Mass Spectrometry for Improved Sensitivity and Repeatability in Glycopeptide Analysis. Analytical chemistry. 2016; 88(11): 5849– 5856. 27119460 source
• Not checked yetcites [57] Snyder CM, Zhou X, Karty JA, Fonslow BR, Novotny MV, Jacobson SC. Capillary electrophoresis-mass spectrometry for direct structural identification of serum N-glycans. Journal of chromatography A. 2017; 1523: 127– 139. 28989033 PMC5691604 source
• Not checked yetcites [58] Medina-Casanellas S, Domínguez-Vega E, Benavente F, Sanz-Nebot V, Somsen GW, de Jong GJ. Low-picomolar analysis of peptides by on-line coupling of fritless solid-phase extraction to sheathless capillary electrophoresis-mass spectrometry. Journal of Chromatography A. 2014; 1328: 1– 6. 24438833 source

In the paper

“Recently, the Kelleher group reported a standard operating procedure for native MS38.”

What the sources say

• Not checked yetcites [38] Schachner LF, Ives AN, McGee JP, Standard Proteoforms and Their Complexes for Native Mass Spectrometry. Journal of the American Society for Mass Spectrometry. 2019. PMC6592724 30963455 source

In the paper

“More recently, Shen and co-workers demonstrated the use of SEC-CZE for analysis of protein complexes and proteoforms under near native conditions21, resulting in the identification of 144 proteins, 672 proteoforms, and 23 protein complexes from the Escherichia coli proteome.”

What the sources say

• Not checked yetcites [21] Shen X, Kou Q, Guo R, Native Proteomics in Discovery Mode Using Size-Exclusion Chromatography-Capillary Zone Electrophoresis-Tandem Mass Spectrometry. Analytical chemistry. 2018; 90(17): 10095– 10099. 30085653 PMC6156775 source

In the paper

“Qu and co-workers reported a LC-CZE strategy for the characterization of site-specific glycan heterogeneity where the use of CZE for analysis of reversed-phase LC glycopeptide fractions reduced the complexity of the sample and enabled glycan structural elucidation88.”

What the sources say

• Not checked yetcites [88] Qu Y, Sun L, Zhang Z, Dovichi NJ. Site-Specific Glycan Heterogeneity Characterization by Hydrophilic Interaction Liquid Chromatography Solid-Phase Extraction, Reversed-Phase Liquid Chromatography Fractionation, and Capillary Zone Electrophoresis-Electrospray Ionization-Tandem Mass Spectrometry. Analytical chemistry. 2018; 90(2): 1223– 1233. 29231704 PMC5771954 source

In the paper

“High peak capacity and resolving power improved the data acquisition, which resulted in an enhanced representation of the proteins in the sample.”

What the sources say

• Not checked yetcites [51] McCool EN, Lubeckyj RA, Shen X, Deep Top-Down Proteomics Using Capillary Zone Electrophoresis-Tandem Mass Spectrometry: Identification of 5700 Proteoforms from the Escherichia coli Proteome. Analytical chemistry. 2018; 90(9): 5529– 5533. 29620868 PMC5930140 source

In the paper

“Notable examples of CZE-MS include the intact mass analysis of biopharmaceutical proteins11 and monoclonal antibodies22,68 where complete baseline separation is often achieved.”

What the sources say

• Not checked yetcites [11] Bush DR, Zang L, Belov AM, Ivanov AR, Karger BL. High Resolution CZE-MS Quantitative Characterization of Intact Biopharmaceutical Proteins: Proteoforms of Interferon-beta1. Analytical chemistry. 2016; 88(2): 1138– 1146. 26641950 source
• Not checked yetcites [22] Han M, Rock BM, Pearson JT, Rock DA. Intact mass analysis of monoclonal antibodies by capillary electrophoresis-Mass spectrometry. Journal of chromatography B, Analytical technologies in the biomedical and life sciences. 2016; 1011: 24– 32. 26751590 source
• Not checked yetcites [68] Zhao Y, Sun L, Knierman MD, Dovichi NJ. Fast separation and analysis of reduced monoclonal antibodies with capillary zone electrophoresis coupled to mass spectrometry. Talanta. 2016; 148: 529– 533. 26653481 source

In the paper

“These authors observed that multi-phosphorylated peptides were poorly retained on the stationary phase of a reversed-phase LC-MS method, resulting in a decreased number of peptide identification relative to the CE-MS analysis.”

What the sources say

• Not checked yetcites [84] Faserl K, Sarg B, Gruber P, Lindner HH. Investigating capillary electrophoresis-mass spectrometry for the analysis of common post-translational modifications. Electrophoresis. 2018; 39(9–10): 1208– 1215. 29389038 PMC6001557 source

In the paper

“Despite the high number of identifications, some limitations were observed, including marginal identifications during the first 20 min of the separation, and a dramatic reduction in identifications after 85 min.”

What the sources say

• Not checked yetcites [46] Zhang Z, Hebert AS, Westphall MS, Qu Y, Coon JJ, Dovichi NJ. Production of Over 27 000 Peptide and Nearly 4400 Protein Identifications by Single-Shot Capillary-Zone Electrophoresis-Mass Spectrometry via Combination of a Very-Low-Electroosmosis Coated Capillary, a Third-Generation Electrokinetically-Pumped Sheath-Flow Nanospray Interface, an Orbitrap Fusion Lumos Tribrid Mass Spectrometer, and an Advanced-Peak-Determination Algorithm. Analytical chemistry. 2018; 90(20): 12090– 12093. 30179504 PMC6508074 source

In the paper

“For instance, Li and co-workers reported a bottom-up strategy that combines the data from CZE-MS and reversed-phase LC-MS91. This combination resulted in an improved number of identified unique peptides where hydrophilic and basic peptides with low molecular weight were predominantly identified via CZE-MS.”

What the sources say

• Not checked yetcites [91] Li Y, Champion MM, Sun L, Champion PAD, Wojcik R, Dovichi NJ. Capillary zone electrophoresis-electrospray ionization-tandem mass spectrometry as an alternative proteomics platform to ultraperformance liquid chromatography-electrospray ionization-tandem mass spectrometry for samples of intermediate complexity. Analytical chemistry. 2012; 84(3): 1617– 1622. 22182061 PMC3277681 source

In the paper

“According to this modeling data, phosphorylation reduces the charge of a peptide, thereby its electrophoretic mobility.”

What the sources say

• Not checked yetcites [86] Chen D, Ludwig KR, Krokhin OV, Capillary Zone Electrophoresis-Tandem Mass Spectrometry for Large-Scale Phosphoproteomics with the Production of over 11,000 Phosphopeptides from the Colon Carcinoma HCT116 Cell Line. Analytical chemistry. 2019; 91(3): 2201– 2208. 30624053 PMC6506858 source

In the paper

“CZE separation has frequently been used to analyze glycosylated peptides and glycans49,57,80,81 and CZE separation via TDMS was used for glycosylation characterization82.”

What the sources say

• Not checked yetcites [49] Qu Y, Sun L, Zhu G, Zhang Z, Peuchen EH, Dovichi NJ. Sensitive and fast characterization of site-specific protein glycosylation with capillary electrophoresis coupled to mass spectrometry. Talanta. 2018; 179: 22– 27. 29310225 PMC5763510 source
• Not checked yetcites [57] Snyder CM, Zhou X, Karty JA, Fonslow BR, Novotny MV, Jacobson SC. Capillary electrophoresis-mass spectrometry for direct structural identification of serum N-glycans. Journal of chromatography A. 2017; 1523: 127– 139. 28989033 PMC5691604 source
• Not checked yetcites [80] Giorgetti J, D’Atri V, Canonge J, Monoclonal antibody N-glycosylation profiling using capillary electrophoresis - Mass spectrometry: Assessment and method validation. Talanta. 2018; 178: 530– 537. 29136858 source
• Not checked yetcites [81] Konermann L Addressing a Common Misconception: Ammonium Acetate as Neutral pH “Buffer” for Native Electrospray Mass Spectrometry. Journal of the American Society for Mass Spectrometry. 2017; 28(9): 1827– 1835. 28710594 source
• Not checked yetcites [82] Yang Y, Franc V, Heck AJR. Glycoproteomics: A Balance between High-Throughput and In-Depth Analysis. Trends in Biotechnology. 2017; 35(7): 598– 609. 28527536 source

In the paper

“Post-translational phosphorylation plays critical roles in biological systems83 and it can also influence the electrophoretic mobility of peptides.”

What the sources say

• Not checked yetcites [83] Mou S, Sun L, Dovichi NJ. Accurate determination of peptide phosphorylation stoichiometry via automated diagonal capillary electrophoresis coupled with mass spectrometry: proof of principle. Analytical chemistry. 2013; 85(22): 10692– 10696. 24144020 PMC3873722 source

In the paper

“CZE has also proven to be a valuable tool for protein identification via bottom-up proteomics where ultrasensitive and fast analysis can be obtained72–74.”

What the sources say

• Not checked yetcites [72] Sun L, Zhu G, Zhao Y, Yan X, Mou S, Dovichi NJ. Ultrasensitive and fast bottom-up analysis of femtogram amounts of complex proteome digests. Angewandte Chemie (International ed in English). 2013; 52(51): 13661– 13664. 24173663 PMC3904452 source
• Not checked yetcites [73] Zhang Z, Dovichi NJ. Optimization of mass spectrometric parameters improve the identification performance of capillary zone electrophoresis for single-shot bottom-up proteomics analysis. Analytica chimica acta. 2018; 1001: 93– 99. 29291811 PMC6159893 source
• Not checked yetcites [74] Zhu G, Sun L, Heidbrink-Thompson J, Capillary zone electrophoresis tandem mass spectrometry detects low concentration host cell impurities in monoclonal antibodies. Electrophoresis. 2016; 37(4): 616– 622. 26530276 PMC4816075 source

In the paper

“Ludwig and co-workers reported a CZE-MS approach that was able to identify over 2,300 phosphorylated peptides in a single analysis85, thus illustrating the advantages of CZE separation over LC for PTM analysis.”

What the sources say

• Not checked yetcites [85] Ludwig KR, Sun L, Zhu G, Dovichi NJ, Hummon AB. Over 2300 phosphorylated peptide identifications with single-shot capillary zone electrophoresis-tandem mass spectrometry in a 100 min separation. Analytical chemistry. 2015; 87(19): 9532– 9537. 26399161 PMC4605816 source

In the paper

“These results demonstrated an increase in sensitivity over analysis after separation using C18 ZipTip only, and highlighted the advantages of using a LC-CZE-MS bottom-up approach.”

What the sources say

• Not checked yetcites [47] Yang Z, Shen X, Chen D, Sun L. Microscale Reversed-Phase Liquid Chromatography/Capillary Zone Electrophoresis-Tandem Mass Spectrometry for Deep and Highly Sensitive Bottom-Up Proteomics: Identification of 7500 Proteins with Five Micrograms of an MCF7 Proteome Digest. Analytical chemistry. 2018; 90(17): 10479– 10486. 30102516 PMC6156779 source

In the paper

“Glycosylation is an important and common PTM in biological systems, but its detailed characterization is challenging because of its heterogeneity in localization and forms76–79.”

What the sources say

• Not checked yetcites [76] Mechref Y, Novotny MV. Glycomic analysis by capillary electrophoresis-mass spectrometry. Mass spectrometry reviews. 2009; 28(2): 207– 222. 18973241 source
• Not checked yetcites [77] Jayo RG, Thaysen-Andersen M, Lindenburg PW, Simple capillary electrophoresis-mass spectrometry method for complex glycan analysis using a flow-through microvial interface. Analytical chemistry. 2014; 86(13): 6479– 6486. 24873509 source
• Not checked yetcites [78] Lu G, Crihfield CL, Gattu S, Veltri LM, Holland LA. Capillary Electrophoresis Separations of Glycans. Chemical reviews. 2018; 118(17): 7867– 7885. 29528644 PMC6135675 source
• Not checked yetcites [79] Mechref Y Analysis of glycans derived from glycoconjugates by capillary electrophoresis-mass spectrometry. Electrophoresis. 2011; 32(24): 3467– 3481. 22180203 PMC3360420 source

In the paper

“The use of acetic acid also increased the migration time of the proteins, which might be attributed to the lower pH of acetic acid that resulted in an increase in hydrodynamics in protein radii, exacerbation of protein unfolding, and reduction of EOF.”

What the sources say

• Not checked yetcites [69] Lubeckyj RA, McCool EN, Shen X, Kou Q, Liu X, Sun L. Single-Shot Top-Down Proteomics with Capillary Zone Electrophoresis-Electrospray Ionization-Tandem Mass Spectrometry for Identification of Nearly 600 Escherichia coli Proteoforms. Analytical chemistry. 2017; 89(22): 12059– 12067. 29064224 PMC5726253 source

In the paper

“Although a BGE with high ionic strength is useful to avoid band broadening, high ionic strength can increase the diffusion of the sample zone and lead to high current and temperature in the separation capillary.”

In the paper

“Interestingly, addition of organic solvents (e.g., propan-2-ol) to an acidic BGE enhances the separation efficiency and MS detection, as demonstrated by Yates group in a top-down analysis of Pyrococcus furiosus proteins using a sheathless interface59.”

What the sources say

• Not checked yetcites [59] Han X, Wang Y, Aslanian A, In-line separation by capillary electrophoresis prior to analysis by top-down mass spectrometry enables sensitive characterization of protein complexes. Journal of proteome research. 2014; 13(12): 6078– 6086. 25382489 PMC4262260 source

In the paper

“In this study, a pH junction injection of 130 nL of BSA resulted in the identification of 40 peptides and produced 70% coverage.”

What the sources say

• Not checked yetcites [119] Zhu G, Sun L, Yan X, Dovichi NJ. Bottom-up proteomics of Escherichia coli using dynamic pH junction preconcentration and capillary zone electrophoresis-electrospray ionization-tandem mass spectrometry. Analytical chemistry. 2014; 86(13): 6331– 6336. 24852005 PMC4082393 source

In the paper

“cIEF has been also reported for the analysis of other intact proteins94.”

What the sources say

• Not checked yetcites [94] Zhu G, Sun L, Dovichi NJ. Simplified capillary isoelectric focusing with chemical mobilization for intact protein analysis. Journal of separation science. 2017; 40(4): 948– 953. 27935257 source

In the paper

“For instance, in a pH lower than ~3.5, migration is predominantly influenced by the basic residues.”

In the paper

“At low pH the free silanols in the capillary wall are protonated and the separation of proteins and peptides is enhanced due to a reduction of the electroosmotic flow (EOF) and reduction of electrostatic interactions.”

In the paper

“Also, it is not compatible with a sheathless interface.”

In the paper

“In this study, 30 proteins were identified from P. aeruginosa PA01 whole cell lysate110.”

What the sources say

• Not checked yetcites [110] Li Y, Compton PD, Tran JC, Ntai I, Kelleher NL. Optimizing capillary electrophoresis for top-down proteomics of 30–80 kDa proteins. Proteomics. 2014; 14(10): 1158– 1164. 24596178 PMC4034378 source

In the paper

“Conversely, sheath-liquid interface is more flexible and an acidic pH can be obtained from the sheath-liquid reservoir, so the BGE pH range can vary between 1 and 8 units.”

In the paper

“The use of positively charged coatings requires the application of negative voltage on the inlet (reversed polarity); as a result, proteins and peptides will migrate in the opposite direction of the EOF.”

In the paper

“This stacking technique relies on the preparation of samples in a basic buffer and injection (with pressure) into the separation capillary. Under application of an electric field, negatively charged proteins or peptides migrate toward the proximal tip of the capillary and are neutralized by an acidic BGE.”

In the paper

“A focused plug is formed and target analytes become positively charged, migrating towards the ESI source25,118.”

What the sources say

• Not checked yetcites [25] Sun L, Zhu G, Yan X, Capillary zone electrophoresis for bottom‐up analysis of complex proteomes. 2016; 16(2): 188– 196. PMC4771184 26508368 source
• Not checked yetcites [118] Zhu G, Sun L, Dovichi NJ. Dynamic pH junction preconcentration in capillary electrophoresis- electrospray ionization-mass spectrometry for proteomics analysis. The Analyst. 2016; 141(18): 5216– 5220. 27460877 PMC5007160 source

In the paper

“As illustrated in Figure 6, high charge states (as in denaturing conditions) were formed in native conditions and their signal intensities increased proportionally to the increase in buffer ionic strength.”

What the sources say

• Not checked yetcites [101] Hedges JB, Vahidi S, Yue X, Konermann L. Effects of ammonium bicarbonate on the electrospray mass spectra of proteins: evidence for bubble-induced unfolding. Analytical chemistry. 2013; 85(13): 6469– 6476. 23724896 source

In the paper

“The bare fused silica capillary produced a marginal separation efficiency for intact proteins and protein complexes as a result of protein adsorption to the capillary wall, whereas the neutral coated capillary generated high separation efficiency by preventing protein adsorption35.”

What the sources say

• Not checked yetcites [35] Belov AM, Viner R, Santos MR, Analysis of Proteins, Protein Complexes, and Organellar Proteomes Using Sheathless Capillary Zone Electrophoresis - Native Mass Spectrometry. Journal of the American Society for Mass Spectrometry. 2017; 28(12): 2614– 2634. 28875426 PMC5709234 source

In the paper

“Ammonium acetate can achieve a pH between 6.8 and 7.4 when dissolved in water and despite a low buffering capacity (ammonium acetate buffers in the pH ranges of 3.8–5.8 and 8.2–10.20, see Table 2), it is often used in native MS.”

In the paper

“Acetonitrile might account for the fast separation and propan-2-ol may provide better resolution of the degradation products.”

In the paper

“In CE-MS applications, the type of interface should also be taken into consideration while choosing a BGE.”

In the paper

“The addition of organic solvent to the BGE reduces the EOF, which results in improved resolution.”

In the paper

“BGE selection is most critical for a sheathless interface because the BGE is the only liquid present during the ESI process and acidic pH is recommended to facilitate protein or peptide ionization efficiency.”

In the paper

“cIEF-MS with a sheath-liquid interface has been used for the analysis of monoclonal antibodies, with Dai et al. reporting the separation of intact monoclonal antibody92. Resolving intact charge variant peaks is a noted challenge, but using this approach, nine charge variants were resolved.”

What the sources say

• Not checked yetcites [92] Dai J, Lamp J, Xia Q, Zhang Y. Capillary Isoelectric Focusing-Mass Spectrometry Method for the Separation and Online Characterization of Intact Monoclonal Antibody Charge Variants. Analytical chemistry. 2018; 90(3): 2246– 2254. 29272582 source

In the paper

“Neutral coating with polyacrylamide is widely used in proteomics research due to its ability to eliminate EOF and maintain effective CE separations.”

In the paper

“This phenomenon might be attributed to the destabilization effects that are induced by the anion bicarbonate, exacerbating the propensity of the protein to unfold during ESI process.”

In the paper

“Many preconcentration techniques to enhance injection volumes in CE-MS applications have been described, based on either electrophoretic (stacking) or chromatographic (solid-phase extraction (SPE)) principles.”

In the paper

“As can be observed in Table 2, these salts (acetate, bicarbonate, and formate) have more than one pKa, which allow their use in more than one pH range.”

In the paper

“Using this set up, Bertoletti et al. were able to preserve protein structure in native conditions and they did not observe the high charge states that are promoted by ammonium bicarbonate, which might be attributed to the lower molar concentration of ammonium bicarbonate in the BGE.”

What the sources say

• Not checked yetcites [102] Bertoletti L, Schappler J, Colombo R, Evaluation of capillary electrophoresis-mass spectrometry for the analysis of the conformational heterogeneity of intact proteins using beta2-microglobulin as model compound. Analytica chimica acta. 2016; 945: 102– 109. 27968711 source

In the paper

“The CE-MS method was found to be linear and precise.”

What the sources say

• Not checked yetcites [128] Varadi C, Mittermayr S, Millan-Martin S, Bones J. Quantitative twoplex glycan analysis using (12)C6 and (13)C6 stable isotope 2-aminobenzoic acid labelling and capillary electrophoresis mass spectrometry. Analytical and bioanalytical chemistry. 2016; 408(30): 8691– 8700. 27662881 source

In the paper

“Despite susceptibility to more technical difficulties and issues than LC-MS, with improvements in instrumentation CE-MS has, in some applications, outperformed conventional LC-based methods (e.g., separation of intact proteins and protein complexes).”

In the paper

“Highly sensitive ionization efficiency can be achieved using both sheathless and sheath-liquid interfaces at lower flow-rate (in the separation capillary) than LC, which reduces background noise and increases MS detectability.”

In the paper

“Bush et al. characterized and quantitated individual molecular proteoforms of interferon-β111.”

What the sources say

• Not checked yetcites [111] Sanchez-Hernandez L, Montealegre C, Kiessig S, Moritz B, Neususs C. In-capillary approach to eliminate SDS interferences in antibody analysis by capillary electrophoresis coupled to mass spectrometry. Electrophoresis. 2017; 38(7): 1044– 1052. 28008632 source

In the paper

“This technology has the advantage that it can be automated and the multistep elution CE can be used as a semi-two-dimensional separation method.”

In the paper

“This approach enabled injections at μL levels with a separation efficiency of over 25,000 theoretical plates.”

What the sources say

• Not checked yetcites [124] Zhang Z, Sun L, Zhu G, Yan X, Dovichi NJ. Integrated strong cation-exchange hybrid monolith coupled with capillary zone electrophoresis and simultaneous dynamic pH junction for large-volume proteomic analysis by mass spectrometry. Talanta. 2015; 138: 117– 122. 25863379 PMC4394190 source

In the paper

“In addition to a detailed proteoform characterization, TDMS can provide structural information of proteins covalently attached to other proteins while native MS provides a detailed information on protein subunit arrangements via non-covalent interactions.”

In the paper

“The same group further eliminated the zero dead volume union by preparing SCX and the neutral coated capillary sequentially in a single fused silica capillary, which resulted in an enhanced protein and peptide identifications when compared to previous reports126.”

What the sources say

• Not checked yetcites [126] Zhang Z, Zhu G, Peuchen EH, Dovichi NJ. Preparation of linear polyacrylamide coating and strong cationic exchange hybrid monolith in a single capillary, and its application as an automated platform for bottom-up proteomics by capillary electrophoresis-mass spectrometry. Microchimica Acta. 2017; 184(3): 921– 925. source

In the paper

“They observed a quantitation limit of 10 pM with a CV lower than 22%121.”

What the sources say

• Not checked yetcites [121] Wang C, Lee CS, Smith RD, Tang KJAc. CITP/CZE-nanoESI-SRM MS via a novel sheathless interface for high sensitivity sample quantification. 2013; 85(15): 7308. PMC3744340 23789856 source

In the paper

“Cross-linking and MS have been successfully used to interrogate protein structures; however, cross-linking reports by CE-MS are scarce.”

In the paper

“Sample loading is the major drawback of CE, which can be addressed using simple protocols, as demonstrated in top-down and bottom-up applications52,87.”

What the sources say

• Not checked yetcites [52] McCool EN, Lubeckyj R, Shen X, Kou Q, Liu X, Sun L. Large-scale Top-down Proteomics Using Capillary Zone Electrophoresis Tandem Mass Spectrometry. Journal of visualized experiments: JoVE. 2018(140). PMC6235596 30417888 source
• Not checked yetcites [87] Wang Y, Fonslow BR, Wong CC, Nakorchevsky A, Yates JR 3rd. Improving the comprehensiveness and sensitivity of sheathless capillary electrophoresis-tandem mass spectrometry for proteomic analysis. Analytical chemistry. 2012; 84(20): 8505– 8513. 23004022 PMC3498465 source

In the paper

“In this strategy, the sample is mixed with two electrolytes, one with very high mobility (leading) and one with very low mobility (terminating). These electrolytes generate a highly conductive zone when separation voltage is applied. Proteins or peptides are then concentrated into zones between the leading and terminating electrolytes.”

In the paper

“Wang et al. used reversed-phase SPE in conjunction with tITP for sample concentration of a Pyrococcus furiosus tryptic digest, which resulted in low background noise and high sensitivity87.”

What the sources say

• Not checked yetcites [87] Wang Y, Fonslow BR, Wong CC, Nakorchevsky A, Yates JR 3rd. Improving the comprehensiveness and sensitivity of sheathless capillary electrophoresis-tandem mass spectrometry for proteomic analysis. Analytical chemistry. 2012; 84(20): 8505– 8513. 23004022 PMC3498465 source

In the paper

“Several bottom-up strategies are available for protein quantification, including stable isotope labeling by amino acids in cell culture (SILAC), isobaric tag for relative and absolute quantitation (iTRAQ), label-free, and isotope-coded affinity tags (ICAT).”

In the paper

“Improvements in interfaces have enhanced the robustness and reproducibility of CE-MS methods, resulting in highly confident identification and characterization of peptides, cellular proteins, PTMs, and protein complexes.”

In the paper

“Sun and co-workers described a quantitative parallel reaction monitoring of peptide abundance where the relative standard deviation (RSD) of the migration time was lower than 4% and the RSD of the fragment ion was approximately 20%132.”

What the sources say

• Not checked yetcites [132] Sun L, Zhu G, Mou S, Zhao Y, Champion MM, Dovichi NJ. Capillary zone electrophoresis-electrospray ionization-tandem mass spectrometry for quantitative parallel reaction monitoring of peptide abundance and single-shot proteomic analysis of a human cell line. Journal of chromatography A. 2014; 1359: 303– 308. 25082526 PMC4141985 source

In the paper

“Transient isotachophoresis (tITP) is a less common stacking approach for preconcentration of peptides and proteins in proteomics research.”

In the paper

“These individual features suggest that TDMS and native MS can be complementary at several levels and can be merged to provide comprehensive protein structural information.”