Tert- butylation of tryptophan (2, 5, 7- tri tertiary butyl tryptophan), formed during acidolytic cleavage of synthetic peptides Ac-KLVYWAE-CONH2 (A-YW) and Ac-KLVWWAE-CONH2 (A-WW), that are analogs of the fragment of Alzheimers β-amyloid peptide Ac-KLVFFAE-CONH2, during solid-phase peptide synthesis, was characterized by matrix- assisted laser desorption/ionization time of flight/time of flight (MALDI TOF/TOF) mass spectrometry. Crude peptide was fractionated by high performance liquid chromatography. Peptide fractions were sequenced and modified tryptophan was determined with the help of MALDI TOF/TOF mass spectra. Thus, it is possible to pinpoint the particular tryptophan residue that undergoes modification during synthesis of peptides containing multiple tryptophan residues.
Keywords: Tryptophan modification, peptide sequence, MALDI TOF/TOF, posttranslational modifications, acetylation
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