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Gas-phase Ion/radical reactionsRadicals play important roles in biological systems via reactions toward a wide variety of biomolecules. We are interested in studying the ion/radical reactions via a gas-phase approach, where mass spectrometry is employed to enable the reactions and also characterize the reaction products. We found hydroxyl radicals can cleave disulfide bonds via dissociation addition. We are studying the fundamental aspects of the reaction and also applying it to characterize peptides/proteins containing disulfide bonds. |
Atmospheric pressure reactor |
MS spectrum of a disulfide peptide after reacting with OH• |
Proposed reaction scheme |
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Improving MS/MS SensitivityTandem mass spectrometry (MS/MS) provides both qualitative and quantitative information on the analyte molecules and offers high discriminating power against noise. In many applications, higher stages of MSn (n>2) are necessary. However, the number of stages that can be executed is limited by the number of ions that remains after each ion isolation step. For ion trap mass spectrometers, their sensitivities are determined by the ion trap capacity. We are developing methods and instrumentation for enriching low abundance MSn product for further analysis on ion trap based mass spectrometers. |
4000 QTRAP -- triple quadrupole/ linear ion trap mass spectrometer |
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Ion formation in Electrospray Ionization (ESI)ESI is regarded as a soft ionization technique for generating intact biomolecular ions. We have found that under low flow speed (nL/min range) and high solution electrical conductivity, ESI can be tuned harsh. Extensive peptide ion backbone fragmentation is typically observed. However, labile phosphate groups are protected during this process. This phenomenon can be used to investigate the underlying principles of ESI, including dynamics and energetics of the process, as well as the nature of analyte-solvent interactions. |
NanoESI-MS Normal Conditions |
NanoESI-MS of Conductive Solutions |
