title: Tryptophan modification by 2-hydroxy-5-nitrobenzyl bromide studied by MALDI-TOF mass spectrometry.
abstract: The reaction with 2-hydroxy-5-nitrobenzyl bromide (HNB) is a common covalent modification of tryptophan. It results in several products which have been described by classical physico-chemical methods. To improve the understanding of the HNB-modified tryptophan structure, we synthesized a model peptide containing one tryptophan only, modified it by HNB, and analyzed the product by MALDI-TOF mass spectrometry. Surprisingly, several multi-modified products (up to 5 HNB moieties per one tryptophan) were identified. the influence of HNB concentration and pH on the degree of modification was also analyzed. In addition, a splitting of modified tryptophan peaks in MALDI-TOF spectrum was described; most probably, this effect is a common MALDI artifact of nitro-aromatic compounds which facilitates the identification of HNB-modified tryptophan by MALDI-TOF MS significantly.
authors.affiliation: Department of Biochemistry and Microbiology, Institute of Chemical Technology, Praha 6, 166 28, Czech Republic.
authors.forename: Martin
authors.initials: M
authors.lastname: Strohalm
authors.forename: Milan
authors.initials: M
authors.lastname: Kodícek
authors.forename: Michal
authors.initials: M
authors.lastname: Pechar
mesh_terms: D015077:2-Hydroxy-5-nitrobenzyl Bromide / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D046911:Macromolecular Substances; D010446:Peptide Fragments; D011485:Protein Binding; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*; D014364:Tryptophan / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D046911:Macromolecular Substances; D010446:Peptide Fragments; D015077:2-Hydroxy-5-nitrobenzyl Bromide; D014364:Tryptophan