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Wan J, Nytka M, Qian H, Vu K, Lemr K, Tureček F. Nitrile Imines as Peptide and Oligonucleotide Photo-Cross-Linkers in Gas-Phase Ions. J Am Soc Mass Spectrom 2024; 35:344-356. [PMID: 38252626 DOI: 10.1021/jasms.3c00379] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Nitrile imines produced by photodissociation of 2,5-diaryltetrazoles undergo cross-linking reactions with amide groups in peptide-tetrazole (tet-peptide) conjugates and a tet-peptide-dinucleotide complex. Tetrazole photodissociation in gas-phase ions is efficient, achieving ca. 50% conversion with 2 laser pulses at 250 nm. The formation of cross-links was detected by CID-MS3 that showed structure-significant dissociations by loss of side-chain groups and internal peptide segments. The structure and composition of cross-linking products were established by a combination of UV-vis action spectroscopy and cyclic ion mobility mass spectrometry (c-IMS). The experimental absorption bands were found to match the bands calculated for vibronic absorption spectra of nitrile imines and cross-linked hydrazone isomers. The calculated collision cross sections (CCSth) for these ions were related to the matching experimental CCSexp from multipass c-IMS measurements. Loss of N2 from tet-peptide conjugates was calculated to be a mildly endothermic reaction with ΔH0 = 80 kJ mol-1 in the gas phase. The excess energy in the photolytically formed nitrile imine is thought to drive endothermic proton transfer, followed by exothermic cyclization to a sterically accessible peptide amide group. The exothermic nitrile imine reaction with peptide amides is promoted by proton transfer and may involve an initial [3 + 2] cycloaddition followed by cleavage of the oxadiazole intermediate. Nucleophilic groups, such as cysteine thiol, did not compete with the amide cyclization. Nitrile imine cross-linking to 2'-deoxycytidylguanosine was found to be >80% efficient and highly specific in targeting guanine. The further potential for exploring nitrile-imine cross-linking for biomolecular structure analysis is discussed.
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Affiliation(s)
- Jiahao Wan
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Marianna Nytka
- Department of Analytical Chemistry, Faculty of Science, Palacky University, 17. listopadu 12, Olomouc 779 00, Czech Republic
| | - Haocheng Qian
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Kim Vu
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Karel Lemr
- Department of Analytical Chemistry, Faculty of Science, Palacky University, 17. listopadu 12, Olomouc 779 00, Czech Republic
- Institute of Microbiology of the Czech Academy of Sciences, Prague 142 20, Czech Republic
| | - František Tureček
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
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Abstract
Photochemical crosslinking in gas-phase ion complexes has been introduced as a method to study biomolecular structures and dynamics. Emphasis has been on carbene-based crosslinking induced by photodissociation of diazirine-tagged ions. The features that characterize gas-phase crosslinking include (1) complex formation in electrospray droplets that allows for library-type screening; (2) well defined stoichiometry of the complexes due to mass-selective isolation; (3) facile reaction monitoring and yield determination, and (4) post-crosslinking structure analysis by tandem mass spectrometry that has been combined with hydrogen-deuterium exchange, UV-vis action spectroscopy, and ion mobility measurements. In this account, examples are given of peptide-peptide, peptide-nucleotide, and peptide-ligand crosslinking that chiefly used carbene-based reactions. The pros and cons of gas-phase crosslinking are discussed. Nitrile-imine based crosslinking in gas-phase ions is introduced as a promising new approach to ion structure analysis that offers high efficiency and has the potential for wide ranging applications.
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Affiliation(s)
- František Tureček
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, WA 98195-1700, USA.
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