Fundamental studies of matrix-assisted laser desorption/ionization
- Oak Ridge National Laboratory, TN (United States)
Matrix-assisted laser desorption/ionization (MALDI) mass spectrometry has been remarkably successful for molecular weight determination of biomolecules. However, the efficiency of ionization, and therefore the sensitivity of the technique, could be improved if details of the ionization mechanism were understood more thoroughly. The chemical and physical environment in the MALDI plume produced by the desorption laser influences the ionization of the analyte, in analogy to the effect of pH on biomolecules in solution. Optical probing techniques, such as laser-induced fluorescence, allow some characteristics of the plume environment to be studied directly. Fluorescence emitted during MALDI experiments using 2,5-dihydroxybenzoic acid (DHB) as the matrix exhibits a broad feature more similar to the emission spectrum of DHB in acidic solution than in neutral or basic solution, suggesting that proton transfer equilibria in the plume can be probed optically. Additionally, narrower features appear in the DHB fluorescence in the MALDI experiment. The origin of these narrow features is not known, but they may be due to emission from small fragments of the matrix, or to cooling of the matrix due to expansion of the plume into the vacuum. In addition to studying the fundamentals of the MALDI ionization mechanism, correlation of plume fluorescence with the efficacy of a given compound as a MALDI matrix may provide a useful optimization tool.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 191706
- Report Number(s):
- CONF-941098--
- Country of Publication:
- United States
- Language:
- English
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