title: The specific cleavage of lactone linkage to open-loop in cyclic lipopeptide during negative ESI tandem mass spectrometry: the hydrogen bond interaction effect of 4-ethyl guaiacol.
abstract: Mass spectrometry is a valuable tool for the analysis and identification of chemical compounds, particularly proteins and peptides. Lichenysins G, the major cyclic lipopeptide of lichenysin, and the non-covalent complex of lichenysins G and 4-ethylguaiacol were investigated with negative ion ESI tandem mass spectrometry. The different fragmentation mechanisms for these compounds were investigated. Our study shows the 4-ethylguaiacol hydrogen bond with the carbonyl oxygen of the ester group in the loop of lichenysins G. With the help of this hydrogen bond interaction, the ring structure preferentially opens in lactone linkage rather than O-C bond of the ester-group to produce alcohol and ketene. Isothermal titration 1H-NMR analysis verified the hydrogen bond and determined the proportion of subject and ligand in the non-covalent complex to be 1∶1. Theoretical calculations also suggest that the addition of the ligand can affect the energy of the transition structures (TS) during loop opening.
authors.affiliation: Department of Chemistry, Zhejiang University, Hangzhou, China.
authors.forename: Mengzhe
authors.initials: M
authors.lastname: Guo
authors.affiliation: College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Youlu
authors.initials: Y
authors.lastname: Pan
authors.affiliation: School of Biotechnology, Jiangnan University, Wuxi, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Zhang
authors.affiliation: College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Yang
authors.initials: Y
authors.lastname: Cao
authors.affiliation: College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.
authors.forename: Jianzhong
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Chemistry, Zhejiang University, Hangzhou, China.
authors.forename: Yuanjiang
authors.initials: Y
authors.lastname: Pan
mesh_terms: D006139:Guaiacol / Q000737:chemistry; D006860:Hydrogen Bonding; D007783:Lactones / Q000737:chemistry*; D055666:Lipopeptides / Q000737:chemistry*; D008074:Lipoproteins / Q000737:chemistry; D010455:Peptides / Q000737:chemistry; D021241:Spectrometry, Mass, Electrospray Ionization; D053719:Tandem Mass Spectrometry
chemical_list: D007783:Lactones; D055666:Lipopeptides; D008074:Lipoproteins; D010455:Peptides; C120178:lichenysin G; D006139:Guaiacol