Resonant two-photon ionization of enkephalins and related peptides volatilized by using pulsed laser desorption in supersonic beam mass spectrometry

1988 ◽  
Vol 60 (14) ◽  
pp. 1409-1415 ◽  
Author(s):  
Liang. Li ◽  
David M. Lubman
Keyword(s):  
Mass Spectrometry ◽  
Pulsed Laser ◽  
Laser Desorption ◽  
Two Photon ◽  
Photon Ionization

Resonant Two-Photon Ionization of CBZ-Derivatized Nonaromatic Peptides Using Pulsed Laser Desorption in Supersonic Beam Mass Spectrometry

1988 ◽  
Vol 42 (3) ◽  
pp. 411-417 ◽  
Author(s):  
Liang Li ◽  
David M. Lubman
Keyword(s):  
Mass Spectrometry ◽  
Mass Spectra ◽  
Pulsed Laser ◽  
Laser Desorption ◽  
Small Peptides ◽  
Neutral Species ◽  
Supersonic Expansion ◽  
Two Photon ◽  
Photon Ionization ◽  
Desorption Method

Resonant two-photon ionization (R2PI) of nonaromatic peptides is studied with the use of CBZ-derivatization as a means of providing an absorbing aromatic center in the near-UV region at 266 nm. The peptides are then vaporized with a pulsed laser-induced desorption method, with subsequent entrainment of the desorbed neutral species into a supersonic expansion. The CBZ-derivatized peptides are then ionized and mass analyzed in a time-of-flight mass spectrometer. The resulting R2PI/MPI-induced fragmentation-ionization patterns generally yield the molecular ion as well as fragments due to specific bond cleavages which are characteristic of the structure of the peptide. Thus, the resulting mass spectra can be used for identification and structural analysis of these small peptides. Most significantly, the laser-induced fragmentation can be used to distinguish between isomeric peptides containing Ile, Leu, or Nle.

Analytical Jet Spectroscopy of Tyrosine and its Analogs Using a Pulsed Laser Desorption Volatilization Method

1988 ◽  
Vol 42 (3) ◽  
pp. 418-424 ◽  
Author(s):  
Liang Li ◽  
David M. Lubman
Keyword(s):  
Structural Changes ◽  
Electronic Spectroscopy ◽  
Supersonic Jet ◽  
Pulsed Laser ◽  
Laser Desorption ◽  
Ultracold Molecules ◽  
Two Photon ◽  
Biological Compounds ◽  
Supersonic Jet Expansion ◽  
Photon Ionization

Pulsed laser desorption is used as a means of volatilizing nonvolatile and thermally labile molecules for entrainment into a supersonic jet expansion. The jet expansion provides ultracold molecules whose sharp spectral features are probed by resonant two-photon ionization spectroscopy in a time-of-flight mass spectrometer. Such jet-cooled spectra are demonstrated for tyrosine and related structural analogs. Despite the similarity between these tyrosine-based compounds, electronic spectroscopy is shown to be a sensitive probe of small structural changes in these related biological compounds.

Resonant Two-Photon Ionization in Biomolecules Using Laser Desorption in Supersonic Beam-Mass Spectrometry

1987 ◽  
Vol 41 (3) ◽  
pp. 431-436 ◽  
Author(s):  
Roger Tembreull ◽  
David M. Lubman
Keyword(s):  
Mass Spectra ◽  
Supersonic Jet ◽  
Pulsed Laser ◽  
Laser Desorption ◽  
Molecular Ions ◽  
Ceramic Surface ◽  
Soft Ionization ◽  
Two Photon ◽  
Photon Ionization ◽  
General Tool

Resonant two-photon ionization (R2PI) has been demonstrated for several classes of biomolecules in a supersonic jet. These thermally labile and nonvolatile species have been vaporized with pulsed laser desorption, with the use of a CO2 laser from a ceramic surface with subsequent entrapment in a jet expansion. R2PI is then demonstrated in a time-of-flight mass spectrometer (TOFMS) with the use of ultraviolet laser radiation at either 280 or 266 nm. The 280-nm wavelength is found to be a fairly general tool for exciting the π-π* transition of the molecules under study, viz., metabolites of catecholamines, indoleamines, and tyrosine near their respective origin regions. The resulting mass spectra exhibit soft ionization where either molecular ions or minimal fragmentation is produced. At frequencies of much higher energy than that of the origin, fragmentation becomes increasingly difficult to prevent.

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