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3-Hydroxy-2-Nitrobenzoic Acid as a MALDI Matrix for In-Source Decay and Evaluation of the Isomers
Yuko Fukuyama1, Shunsuke Izumi2, Koichi Tanaka3
1Koichi Tanaka Mass Spectrometry Research Laboratory, Shimadzu Corporation, 1, Nishinokyo Kuwabara-cho, Nakagyo-ku, Kyoto, 604-8511, Japan. yukof@shimadzu.co.jp.
Journal of the American Society for Mass Spectrometry
|August 1, 2018
Summary
This study evaluates 3-hydroxy-4-nitrobenzoic acid isomers as oxidizing matrices for in-source decay mass spectrometry. 3H2NBA demonstrated superior performance, offering high sensitivity and resolution for peptide analysis in MALDI-MS.
Area of Science:
- Analytical Chemistry
- Mass Spectrometry
- Proteomics
Background:
- In-source decay (ISD) in matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) is crucial for peptide sequencing.
- Reducing matrices like 1,5-diaminonaphthalene (1,5-DAN) offer high sensitivity but struggle with leucine/isoleucine differentiation and proline-induced fragment loss.
- Oxidizing matrices overcome these limitations by generating a- and d-series ions, but often exhibit lower sensitivity compared to reducing matrices.
Purpose of the Study:
- To evaluate various 3-hydroxy-4-nitrobenzoic acid (3H4NBA) isomers as potential oxidizing matrices for ISD-MALDI-MS.
- To compare the performance of these isomers against established reducing and oxidizing matrices.
- To identify novel oxidizing matrices that enhance sensitivity and resolution in peptide analysis.
Main Methods:
- Synthesis and evaluation of 3H4NBA isomers (2H3NBA, 2H4NBA, 2H5NBA, 2H6NBA, 3H2NBA, 3H5NBA, 4H2NBA, 4H3NBA, 5H2NBA, and 3H4NBA).
- Application of these matrices in in-source decay (ISD) experiments using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS).
- Analysis of generated fragment ions (a- and d-series) for peptide samples, focusing on peak intensity and resolution.
Main Results:
- All evaluated 3H4NBA isomers generated characteristic a- and d-series ions.
- 3H2NBA, 3H5NBA, 4H2NBA, 4H3NBA, and 5H2NBA were identified as novel oxidizing matrices for ISD.
- 3H2NBA and 4H3NBA showed higher peak intensity for a-series ions compared to 3H4NBA.
- 3H2NBA exhibited comparable or higher intensity and significantly better peak resolution than 1,5-DAN for certain peptides.
Conclusions:
- 3H2NBA emerges as a highly effective oxidizing matrix for ISD-MALDI-MS, surpassing conventional matrices in certain aspects.
- The findings suggest that 3H2NBA can significantly improve peptide sequencing accuracy and sensitivity.
- This research expands the toolkit of matrices available for advanced proteomic analyses using MALDI-MS.
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