Dataset Information

Micro-scale RPLC-CZE-MS/MS for deep and highly sensitive bottom-up proteomics

ABSTRACT: Capillary zone electrophoresis-tandem mass spectrometry (CZE-MS/MS) has been well recognized for bottom-up proteomics. It has approached 4000-8000 protein identifications (IDs) from a human cell line, mouse brains or Xenopus embryos via coupling with liquid chromatography (LC) prefractionation. However, at least five hundred micrograms of complex proteome digests were required for the LC-CZE-MS/MS studies. This requirement of a large amount of initial peptide material impedes the application of CZE-MS/MS for deep bottom-up proteomics of mass-limited samples. In this work, we coupled micro-scale reversed-phase LC (µRPLC) based peptide prefractionation to dynamic pH junction based CZE-MS/MS for deep bottom-up proteomics of the MCF7 breast cancer cell proteome starting with only 5-µg peptides. The dynamic pH junction based CZE enabled a 500-nL sample injection from as low as a 1.5-µL peptide sample, using up to 33% of the available peptide material for an analysis. Two kinds of µRPLC prefractionation were investigated, C18 ZipTip and nanoflow RPLC. C18 ZipTip-CZE-MS/MS identified 4453 proteins from 5 µg of the MCF7 proteome digest and showed good qualitative and quantitative reproducibility. Nanoflow RPLC-CZE-MS/MS produced over 7500 protein IDs and nearly 60000 peptide IDs from the 5-µg MCF7 proteome digest. The nanoflow RPLC-CZE-MS/MS platform reduced the required amount of complex proteome digests for LC-CZE-MS/MS-based deep bottom-up proteomics by two orders of magnitude. Our work provides the proteomicscommunity with a powerful tool for deep and highly sensitive proteomics.

INSTRUMENT(S): Q Exactive

ORGANISM(S): Homo Sapiens (human)

SUBMITTER: Liangliang Sun

LAB HEAD: Liangliang Sun

PROVIDER: PXD009991 | Pride | 2018-08-16

REPOSITORIES: Pride

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Publications

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.

Yang Zhichang Z Shen Xiaojing X Chen Daoyang D Sun Liangliang L

Analytical chemistry 20180823 17

Capillary zone electrophoresis-tandem mass spectrometry (CZE-MS/MS) has been well recognized for bottom-up proteomics. It has approached 4000-8000 protein identifications (IDs) from a human cell line, mouse brains, or Xenopus embryos via coupling with liquid chromatography (LC) prefractionation. However, at least 500 μg of complex proteome digests were required for the LC/CZE-MS/MS studies. This requirement of a large amount of initial peptide material impedes the application of CZE-MS/MS for de ...[more]

PMID: 30102516

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Project description:Two-dimensional (2D) liquid chromatography (LC)-tandem mass spectrometry (MS/MS) are typically employed for deep bottom-up proteomics, and the state-of-the-art 2D-LC-MS/MS has approached over 8,000 protein identifications (IDs) from mammalian cell lines or tissues in 1-3 days of mass spectrometer time. Capillary zone electrophoresis (CZE)-MS/MS has been suggested as an alternative to LC-MS/MS for bottom-up proteomics. CZE-MS/MS and LC-MS/MS are complementary in protein/peptide ID from complex proteome digests because CZE and LC are orthogonal for peptide separation. In addition, the migration time of peptides from CZE-MS can be predicted accurately, which is invaluable for evaluating the confidence of peptide ID from the database search and even guiding the database search. However, the number of protein IDs from complex proteomes using CZE-MS/MS is still much lower than the state of the art using 2D-LC-MS/MS. In this work, for the first time, we established a strong cation exchange (SCX)-reversed phase LC (RPLC)-CZE-MS/MS platform for deep bottom-up proteomics. The platform identified around 8,200 protein groups and 65,000 unique peptides from a mouse brain proteome digest in 70 hours. The data represents the largest bottom-up proteomics dataset using CZE-MS/MS and provides a valuable resource for further improving the tool for prediction of peptide migration time in CZE. The peak capacity of the orthogonal SCX-RPLC-CZE platform was estimated to be around 7,000. SCX-RPLC-CZE-MS/MS produced comparable numbers of protein and peptide IDs with 2D-LC-MS/MS (8,200 vs. 8,900 protein groups, 65,000 vs. 70,000 unique peptides) from the mouse brain proteome digest using comparable instrument time. This is the first time that CZE-MS/MS showed its capability to approach comparable performance to the state-of-the-art 2D-LC-MS/MS for deep proteomic sequencing. SCX-RPLC-CZE-MS/MS and 2D-LC-MS/MS showed good complementarity in protein and peptide IDs and combining those two methods improved the number of protein group and unique peptide IDs by nearly 10% and over 40%, respectively, compared with 2D-LC-MS/MS alone.

Project description:Recent advances in mass spectrometric (MS) instruments resulting in high mass resolution and high duty cycles have allowed of very deep coverage of proteomes. However, even with state of the art, high duty cycle instruments, the number of proteins identified with a conventional single liquid chromatography-tandem MS (LC/MS/MS) analysis is typically limited and fractionating protein samples prior to LC/MS/MS analysis is crucial for increasing both the analytical dynamic range and proteome coverage. In order to achieve near comprehensive identification of proteomes two-dimensional (2D) chromatography has been an invaluable tool. This first dimension is typically performed with µL/min flow and relatively large column inner diameters, which allow efficient pre-fractionation but typically require peptide amounts in the milligram range while the second dimension is typically performed with nL/min flow rates and capillary columns with small inner diameters. Typically, reverse phase liquid chromatography (RPLC) provides high peak resolution of peptides and achieves higher peak capacities than strong cation exchange chromatography (SCX) due to the faster chromatographic partitioning. Another advantage of RPLC is that the mobile phases used generate much cleaner samples for downstream analyses, while the incorporation of a desalting step for SCX in order to eliminated the high salt concentrations that can significantly decrease the analytical sensitivity of the MS analysis due to ionization problems. When operated at widely different pH values (e.g., 1st dimension pH 10 and 2nd dimension pH 3) 2D RPLC-RPLC provides separation orthogonality comparable to that of the combination of SCX-RPLC. The difference of separation selectivity between the low and high pH (HpH) RPLC comes from the changes in the charge distribution within peptide chains upon altering pH of the eluent. Herein we describe a method in which tryptic peptides are separated in the first dimension by HpH-RPLC and fractions are collected every 90 s over an 80 min gradient. For the second dimension, each of these fractions is individually run by the standard low pH RPLC method. The implementation of the HpH pre-fractionation allows for short second dimension gradients for bottom up LC/MS/MS and yields very deep (e.g. thousands of identifications) protein coverage at reasonable measurement time.

Dataset Information

Micro-scale RPLC-CZE-MS/MS for deep and highly sensitive bottom-up proteomics

Publications

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.

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