Analysis of Initial Reactions of MALDI Based on Chemical Properties of Matrixes and Excitation Condition

Yin-Hung Lai, Chia Chen Wang, Chiu Wen Chen, Bo-Hong Liu, Sheng Hsien Lin, Yuan Tseh Lee, Yi Sheng Wang

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14 Scopus citations

Abstract

This investigation concerns the initial chemical reactions that affect the ionization of matrixes in matrix-assisted laser desorption/ionization (MALDI). The study focuses on the relaxations of photon energy that occur on a comparable time scale to that of ionization, in which the available laser energy is shared and the ionization condition is changed. The relaxations include fluorescence, fragmentation, and nonradiative relaxation from the excited state to the ground state. With high absorption cross section and long excited-state lifetime, photoionization of matrix plays an important role if sufficient laser energy is used. Under other conditions, thermal ionization of the molecule in the ground state is predicted to be one of the important reactions. Evidence of change in the branching ratio of initial reactions with the matrix and the excitation wavelength was obtained with alpha-cyano-4-hydroxycinnamic acid, sinapinic acid, 2,5-dihydroxybenzoic acid, and 2,4,6-trihydroxyacetophenone. These matrixes are studied by obtaining their mixed crystal absorption spectra, fluorescence properties, laser-induced infrared emission, and product ions. The exact ionization pathway depends on the chemical properties of matrixes and the excitation conditions. This concept may explain the diversity of experimental results observed in MALDI experiments, which provides an insight into the ensemble of chemical reactions that govern the generation of ions.
Original languageEnglish
Pages (from-to)9635-9643
Number of pages9
JournalJournal of Physical Chemistry B
Volume116
Issue number32
DOIs
StatePublished - 16 Aug 2012

Keywords

  • ASSISTED-LASER-DESORPTION/IONIZATION; TIME-OF-FLIGHT; IONIZATION MASS-SPECTROMETRY; DESORPTION IONIZATION; ION FORMATION; 2,5-DIHYDROXYBENZOIC ACID; INTERNAL ENERGY; SINAPINIC ACID; NEGATIVE-IONS; LUMINESCENCE SPECTROSCOPY

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