2018 Fiscal Year Research-status Report
Energy-resolved tandem mass spectrometry for in-situ differentiation and identification of isomers
| Project/Area Number |
17K08262
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
中村 健道 国立研究開発法人理化学研究所, 環境資源科学研究センター, 専任研究員 (10360611)
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| Project Period (FY) |
2017-04-01 – 2020-03-31
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| Keywords | Energy-resolved MS/MS / Isomer Differentiation / CID / Ion Mobility / Collision Cross Section / Breakdown Diagram / Chemical Fingerprinting |
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| Outline of Annual Research Achievements |
As collision-induced dissociation (CID) tandem mass spectrometry (MS2) product ion spectra are highly condition/platform-dependent, MS2 spectral libraries do not work well for compound identification by spectral pattern matching. Obviously, lab-frame collision energy (CE) strongly affects spectral patterns. The patterns also depend on other conditions including collision gas species and collision cell pressure. The MS2 data can be considered as a function of internal energy distribution. Therefore, we pursue potential utility of breakdown diagrams (BDs) obtained by energy-resolved (ER) experiments for chemical fingerprinting. To this end, we developed a new method for capturing ER-MS2 data by taking advantage of the acquisition architecture of an existing Q-TOF platform.
A Waters Synapt G2 instrument was used with extensively modified conditions. Briefly, data were acquired in ion mobility (IM) mode with no He/N2 gas so that ions were simply driven through the IM cell to the transfer collision cell where CID occurs. Lab-frame collision energy was ramped in 200 steps (each corresponds to one push cycle) and stored in 200 bins that were grouped in each "scan". Post processing of the data in 200 bins allowed reconstruction of ER-MS2 data sets and BDs. The BDs change as the gas species and pressure changes; onsets/maxima against lab-frame CE shift. However, the characteristics of each fragmentation channels including the orders of onsets and maxima were preserved; the potential utility of BDs for fingerprinting of organic molecules was shown.
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| Current Status of Research Progress |
Current Status of Research Progress
3: Progress in research has been slightly delayed.
Reason
Additional gas plumbing/switching for collision gas switching was fabricated to the existing Synapt G2 experimental platform and He, Ne, and N2 have now become available as routine optional collision gas. With the new acquisition procedure we've developed on the ion mobility hybrid system, it turned out to be advantageous to have optional switching valves for buffer gasses. As the existing machine becomes a little insensitive to current standards, we are establishing collaboration with instrument manufacturers for having our method tested in the latest platforms.
While we continue to refine/improve the acquisition workflow with the Q-TOF systems as we planned, we also tried to adapt the workflow to a triple quadrupole system available as a shared resource in our organization. However, unfortunately, the machine has broken in the course of experimental setup by some reasons. As a result, we needed to wait until next fiscal year for the repair of shared instrument.
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| Strategy for Future Research Activity |
We set up a computational platform for systematic search of transition states in competing fragmentation channels of small systems including protonated amino acids in gas-phase. This approach will be incorporated to the modeling and evaluation of transition-state energy barriers of small metabolites whose molecular mass is around 100 and above. The effort to push automation of data acquisition and handling to be continued; we also improve the method for data visualization, which shall facilitate application of ER-MS2 dataset in various ways.
In the meantime, we continue to compile experimental data of for small drug-related molecules in addition to metabolites. We also plan to extend the external collaboration to accelerate the data compilation and applications. The issue regarding cross-platform standardization of the energy axis and mass discrimination at lower m/z range yet remains to be resolved. We hope the additional data to be acquired with the triple-quad instrumentation shall guide us the way to correct instrumentation factors in a reasonable data handling.
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| Causes of Carryover |
Due to the slight delay caused by machine trouble, etc., some of the experiments planned in this year have been postponed. Additional hardware modifications including the switching valves for buffer gasses shall be made. For the automation of data acquisition, processing, and the computational studies, some customization of software will be necessary. We also anticipate the needs for some additional software for establishing an efficient way for data visualization.
We plan to continue the effort for acquisition and compilation of the experimental ER-MS/MS data and theoretical data in the fiscal year 2019 onward, surplus funds is planned to be used for purchase of additional software, hardware and chemicals for data compilation.
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Research Products
(3 results)
