ABSTRACT
We report collision-induced dissociation (CID) and laser-induced dissociation (LID) performed at different wavelengths between 220 and 280 nm of the peptides leucine-enkephalin (protonated) and gramicidin A (sodiated). Hydrogen-atom losses and side-chain cleavages were observed in LID experiments. These losses depend on the laser wavelength and lead to the formation of radical ions. The fragmentations of these radicals, which are not observed in CID experiments, were investigated in multi-stage mass spectrometry experiments.
Subject(s)
Enkephalin, Leucine/analysis , Enkephalin, Leucine/radiation effects , Gramicidin/analysis , Gramicidin/radiation effects , Peptide Mapping/methods , Photochemistry/methods , Spectrometry, Mass, Electrospray Ionization/methods , Equipment Design , Equipment Failure Analysis , Lasers , Peptide Mapping/instrumentation , Peptides/analysis , Peptides/radiation effects , Spectrometry, Mass, Electrospray Ionization/instrumentation , Ultraviolet RaysSubject(s)
Affinity Labels/chemistry , Affinity Labels/chemical synthesis , Biotin , Photochemistry , Affinity Labels/radiation effects , Biotechnology , Drug Design , Enkephalin, Leucine/analogs & derivatives , Enkephalin, Leucine/chemistry , Enkephalin, Leucine/radiation effects , Indicators and Reagents , Oligonucleotides/chemical synthesis , Oligonucleotides/chemistry , Oligonucleotides/radiation effectsABSTRACT
The binding site specificity of crosslinking mediated by the hydroxyl radical has been investigated in a simple model system: a tetrapeptide, Gly-Gly-Phe-Leu, and 14C-labeled phenylalanine. Crosslinking leads to the tetrapeptide-phenylalanine adduct which has been isolated by gel filtration. The amino acid analysis of these adducts compared with those of gamma-radiation-induced dimers of the tetrapeptide and of the dipeptide, Gly-Phe, shows that only the phenylalanine residue is affected and that the same new peaks appear in each case. Spectrophotometric measurement indicates that the extinction coefficient at 260 nm of dimeric tetrapeptide is four times higher than that of monomeric, as is dimeric phenylalanine compared to monomeric. These observations suggest a common crosslinking mechanism in all three cases that involves the aromatic ring of phenylalanine. The appearance of several radioactive peaks in the gel filtration separation of the acid hydrolysate of the adduct suggests that the crosslinking involves more than one possible modification of the phenylalanine. Three distinct tetrapeptide-Phe species, corresponding to molecular weights of 555, 573, and 591, were observed by fast atom bombardment mass spectrometry. The partial release of radioactive phenylalanine from the tetrapeptide-phenylalanine adducts by acid hydrolysis indicates the liability of some phenylalanine-phenylalanine bonds.
