| Summary: | 博士 === 臺灣大學 === 化學研究所 === 98 === Laser Desorption Proton Transfer Reaction Mass Spectrometry (LD-PTR-MS), a novel technique which combines Laser Desorption (LD) method with Proton Transfer Reaction-Mass Spectrometry (PTR-MS), had been developed and studied in this work. LD-PTR-MS can be utilized to detect nonvolatile compounds on surface, especially biomolecules including peptides, proteins and carbohydrates. The analytes are desorbed into the gas-phase by laser irradiance, collide with the reagent ions, and then are ionized via proton transfer reactions. A home-made hollow cathode discharge (HCD) device was employed to generate the reagent ions. The optimum reagent ions for biomolecules were found to be water or ammonia solvated protons, that is, H+(H2O)n or H+(NH3)m. Protnated-molecular ions were the most dominant features in LD-PTR-MS mass spectra while fragmentation was minimized by the reduction of reaction exoergicity and evaporative cooling effect when using solvated protons as the reagent ions. Mass analysis was done by a home-built linear time-of-flight mass spectrometry (TOF-MS).
In this work, a various types of reagent ions and laser desorption schemes have been investigated to seek the optimum processing conditions for LD-PTR. The reagent ions tested include H3+, H3O+, NH4+, H+(H2O)n, and H+(NH3)m. And the laser desorption schemes employed can be classified into graphite assisted (GA), matrix assisted (MA), ionic liquid matrix assisted (ILMA) and icy matrix assisted (IMA) laser desorption.
LD-PTR-MS has the following features: to softly ionize biomolecules; to examine the neutrals within LD plume and unravel the mechanisms involved; and to extend the application of PTR-MS from volatile organic compounds (VOCs) to nonvolatile compounds; to provide a new tool to study proton transfer reaction of biomolecules in the gas-phase, especially carbohydrates which are in lack of corresponding literature; to enhance the ionization efficiency of biological mass spectrometry; to post-ionize biomolecules by the most sensitive technology, PTR-MS; to support the idea of that “gas-phase proton transfer reaction played an important role in MALDI mechanism.”
Part of the results was presented in oral in the Instruments & Technology session at the 4th International Conference on Proton Transfer Reaction-Mass Spectrometry and its Applications, in Obergurgl, Austria, February 16-21, 2009. It was also presented at the 236th American Chemical Society National Meeting& Exposition, in Philadelphia, PA, August 17-21, 2008; and at the 238th American Chemical Society National Meeting& Exposition, in Washington, D.C., August 16-20, 2009.
|
|---|
