Investigation of the biologically relevant amino acids and some small peptides by laser induced mass spectrometry

Schiller, Ch.; Kupka, K.; Hillenkamp, Franz

doi:10.1007/bf00479645

Cited by 14 publications

(8 citation statements)

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“…The SIMS mass spectra we obtain are similar to previously reported amino acid mass spectra. ,− All the aliphatic amino acid SIMS mass spectra exhibit the formation of the quasimolecular ion (M + H) + and decarboxylated ion (M − COOH) + . These two ions are also commonly observed in laser desorption mass spectrometry of amino acids. − The quasimolecular ion is stabilized by the additional proton which removes the radical site on the amine in addition to providing a positive charge. The positive ion SIMS spectrum of leucine is shown in Figure .…”

Section: Resultsmentioning

confidence: 97%

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Femtosecond Photoionization of Ion Beam Desorbed Aliphatic and Aromatic Amino Acids: Fragmentation via α-Cleavage Reactions

et al. 1999

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We report the photoionization of ion beam desorbed amino acids using femtosecond laser pulses at 195 and 260 nm. Ionization of ion-desorbed glycine, alanine, valine, leucine, isoleucine, and phenylalanine using 195 nm laser pulses is found to produce almost exclusively a decarboxylated ion fragment, while tyrosine and tryptophan produce a functional group cation. The adiabatic ionization potentials for the former amino acids correspond to the removal of an electron from the amine nitrogen atom, while for tyrosine and tryptophan it corresponds to the removal of an electron from the aromatic functional group. We find that fragmentation is initiated by the formation of a radical site which leads to an α-cleavage reaction and, depending upon which electron is removed, results in the formation of a decarboxylated ion or a functional group ion. These results indicate that a significant fraction of the amino acids are desorbed intact, but are fragmented when ionized. Except for leucine, isoleucine, and phenylalanine, the mass spectra produced by 260 nm irradiation are similar to the mass spectra produced by 195 nm irradiation. When using these two wavelengths, the desorbed amino acids exhibit a 2- to 8-fold higher ion yield than is found using only secondary ions produced directly by the incident ion beam. Tyrosine exhibits up to a 40-fold increase in signal using 195 nm irradiation.

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Section: Resultsmentioning

confidence: 97%

“…These two ions are also commonly observed in laser desorption mass spectrometry of amino acids. [43][44][45][46][47] The quasimolecular ion is stabilized by the additional proton which removes the radical site on the amine in addition to providing a positive charge. The positive ion SIMS spectrum of leucine is shown in Figure 6.…”

Section: Resultsmentioning

confidence: 99%

Femtosecond Photoionization of Ion Beam Desorbed Aliphatic and Aromatic Amino Acids: Fragmentation via α-Cleavage Reactions

et al. 1999

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“…Laser mass spectrometry (LMS) studies have been reported for a number of different organic compounds (1)(2)(3). Many of these compounds show intense protonated and deprotonated molecular ions, (M + H)+ ánd ( -H)~.…”

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confidence: 99%

“…HA(s,g) -H+(g) + A"(g) acid/base production from HA (2) RCOOH(g) + H+(g) -»• RCOOH2+(g) protonation (3) RCOOH(g) + A"(g) -RCOO-(g) + HA(g) proton abstraction (4) In eq 2-4, H+(g) and A"(g) have been written as general Bronsted acids and bases.…”

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confidence: 99%

“…studied the LMS of several amino acids in which (1) the alkyl chain has been completely deuterated and (2) the carboxylic acid and amino acid functional groups have been deuterated. By observing the protonated and deprotonated molecular ions at laser energies near and well above threshold, we were able to determine that random gas-phase protonation does not constitute a major ionization mechanism and that intermolecular proton transfer is probably a major pathway in laser mass spectrometry.…”

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