Multiphoton ionization and photodissociation at the second-order space focus in a time-of-flight mass spectrometer: The amino acid tryptophan
✍ Scribed by Michael Dey; Jürgen Grotemeyer
- Publisher
- John Wiley and Sons
- Year
- 1994
- Tongue
- English
- Weight
- 859 KB
- Volume
- 29
- Category
- Article
- ISSN
- 1076-5174
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✦ Synopsis
Neutral IR-desorbed molecules of the amino acid tryptophan entrained in a supersonic beam were post-ionized by multiphoton ionization (MUPI) in the gas phase. Variations in the intensity of the ionization laser produced different degrees of fragmentation observed in the time-of-flight mass spectra of tryptophan according to the ladderswitching model for MUPI fragmentation. From the number of absorbed photons the upper values for the appearance energies of specific fragment ions were obtained. A complete fragmentation pathway of tryptophan was established by using photodissociation of molecular ions and fragment ions formed by MUPI. Photodissociation was successfully performed by secondary excitation with a UV laser at the second-order space focus of a reflection time-of-flight instrument. A fragmentation tree for a laser-desorbed molecule obtained in a laser tandem time-offlight instrument is shown for the first time.