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Zhang W, Yang C, Liu J, Liang Z, Shan Y, Zhang L, Zhang Y. Accurate discrimination of leucine and isoleucine residues by combining continuous digestion with multiple MS 3 spectra integration in protein sequence. Talanta 2022; 249:123666. [PMID: 35717752 DOI: 10.1016/j.talanta.2022.123666] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 06/07/2022] [Accepted: 06/08/2022] [Indexed: 12/26/2022]
Abstract
Protein de novo sequencing based on tandem mass spectrometry is a crucial technology that enables the identification of peptides without searching databases and assembling unknown sequence proteins, especially for monoclonal antibodies (mAbs). However, the discrimination of leucine (Leu) and isoleucine (Ile) residues in the target protein sequence is still challenging. Herein, we developed an accurate method by continuous digestion with MS3-based fragmentation and multiple spectra integration (evaluated by combined verification score, CVS) to distinguish Leu and Ile residues. Continuous digestion promotes the diversity of peptides in order to expose more Leu and Ile at the N-terminal. CVS integrates multiple MS3 spectra to reduce the interference from noise and co-fragmented ions and improve accuracy. This method successfully resolved all 75 Leu/Ile in bovine serum albumin, especially 3 consecutive Leu/Ile. We further applied the method to analyze trastuzumab and 67 out of the 68 Leu/Ile from the light chain and heavy chain were accurately discriminated, demonstrating the great potential in mAbs sequencing.
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Affiliation(s)
- Weijie Zhang
- CAS Key Laboratory of Separation Science for Analytical Chemistry, National Chromatographic R. & A. Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China; University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Chao Yang
- CAS Key Laboratory of Separation Science for Analytical Chemistry, National Chromatographic R. & A. Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China; University of Chinese Academy of Sciences, Beijing, 100039, China
| | - Jianhui Liu
- CAS Key Laboratory of Separation Science for Analytical Chemistry, National Chromatographic R. & A. Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Zhen Liang
- CAS Key Laboratory of Separation Science for Analytical Chemistry, National Chromatographic R. & A. Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
| | - Yichu Shan
- CAS Key Laboratory of Separation Science for Analytical Chemistry, National Chromatographic R. & A. Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China.
| | - Lihua Zhang
- CAS Key Laboratory of Separation Science for Analytical Chemistry, National Chromatographic R. & A. Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China.
| | - Yukui Zhang
- CAS Key Laboratory of Separation Science for Analytical Chemistry, National Chromatographic R. & A. Center, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, Liaoning, 116023, China
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