In-source decay characteristics of peptides in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.
In-source decay (ISD) of peptides, coupled with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, has been examined to determine the influence of the matrix, the susceptibility of amino-acid residues to ISD, and the effect of extraction delay times. Out of nine di- and tri-hydroxybenzoic acids and three cinnamic derivatives tested, the most suitable matrix for ISD was 2,5-dihydroxybenzoic acid. The amine bond at Xxx-Gly and Xxx-Val residues was less susceptible than other amino-acid residues to ISD; however, the more sensitive residue(s) were not as clear. Using a peptide that gave the y(n)- and (z(n) + 2)-series product ions, it was confirmed that amide-bond cleavage (formation of the y(n)-series ions) accompanied metastable peaks, whereas metastable peaks were never observed with amine-bond cleavage [formation of the (z(n) + 2)-series ions]. Furthermore, abundant c(n)-series ions, which originate from amine-bond cleavage on the peptide backbone, were observed whenever a minimum delay time of 38 ns or continuous extraction was used to obtain spectra. These data indicate that amine-bond cleavage in ISD takes place on the ionization time scale before the energy randomization is completed.
Takayama
M
M
Pharmaceutical Sciences, Toho University, Funabashi, Chiba, Japan. takayama@phar.toho-u.ac.jp
D000324:Adrenocorticotropic Hormone / Q000737:chemistry; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D053497:Corticotropin-Like Intermediate Lobe Peptide; D005841:Gentisates; D062385:Hydroxybenzoates; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D010455:Peptides / Q000737:chemistry*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
D000596:Amino Acids; D005841:Gentisates; D062385:Hydroxybenzoates; D010446:Peptide Fragments; D010455:Peptides; D053497:Corticotropin-Like Intermediate Lobe Peptide; D000324:Adrenocorticotropic Hormone; C010925:2,5-dihydroxybenzoic acid