The Total Charge of Carbon and Nitrogen Atoms in the Amide Bonds Acts as a New Approach to Understand the Mobile Proton Model |
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| Authors: | Qifei Xu Wansong Zong Longping Shi |
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| Institution: | 1. Shandong Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, China-America CRC for Environment and Health , Shandong University , Jinan , Shandong Province , P.R. China;2. College of Population, Resources and Environmental Sciences , Shandong Normal University , Jinan , PR China;3. Shandong Pesticide Research Institute , Jinan , Shandong , China |
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| Abstract: | The mobile proton model has been the main theory to describe peptide fragmentation in mass spectrometry (MS). In this study, Gly-Ala-Tyr (GAY) was used to research the mass spectrometry cleavage mechanism. The hydroxyl radical oxidation technique was applied to change the charge distribution of the peptide. We applied MS/MS technique to obtain the tandem mass spectrum of the peptide and then obtained fragmentation efficiency curves, which indicated that the cleavage of GAY became more and more difficult as more O atoms were added. The charge distribution was obtained from quantum chemical calculations at the B3LYP/6-31G(d) level using the Gaussian 03 W program. By analyzing the charge distribution around the amide bonds, we found that the total charge of C and N atoms (QC + QN) in the amide bonds provided a reasonable prediction of peptide fragmentation efficiency. A decrease of the QC + QN value in the amide bonds leads to a low fragmentation efficiency of GAY, and vice versa. Through comparing experimental data with calculation results to research the relationship between charge distribution and the mass spectrometry cleavage mechanism, this work provides a new way to understand the mobile proton model for peptide fragmentation. |
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| Keywords: | charge distribution fragmentation efficiency curves oxidation sites quantum chemical calculations tandem mass spectrometry |
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