ISSN:
0030-493X
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The mechanism of fragment ion formation in resonance-enhanced multiphoton ionization (REMPI) of benzyloxycarbonyl (CBZ)-derivitized dipeptides is presented. At 266 nm, the entire multiphoton process can be thought of as a two-part scheme where ionization occurs by resonant two-photon ionization followed by photodissociation of the created ions. When the energy of two photons exceeds the molecular ionization energy by a significant amount, REMPI has the advantage of producing both parent ions and low appearance energy fragments in large amounts. For CBZ dipeptides, resonant two-photon ionization at 266 nm produces parent ions as well as A type sequence ions with high abundance. On the other hand, a three-photon process (resonant two-photon ionization followed by parent ion photodissociation) forms sequence-related ions which also involve complex fragmentations of the CBZ chromophore. These results are compared to mass spectra obtained by other ionization/dissociation methods and to REMPI mass spectra of related compounds. Factors related to molecular structure elucidation based upon REMPI mass spectra are discussed. Enhanced isomer distinction is demonstrated for CBZ-leu-ala-OCH3 and CBZ-ile-ala-OCH3 based upon REMPI fragmentation.
Additional Material:
4 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/oms.1210240307
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