EFFICIENT PEPTIDE LADDER SEQUENCING BY MALDI-TOF MASS-SPECTROMETRY USING ALLYL ISOTHIOCYANATE

A new modification of the peptide ladder sequencing technique is descr ibed in which allyl isothiocyanate (AITC) replaces trifluoroethyl isot hiocyanate as the volatile amine-modification reagent. AITC is commerc ially available, readily purified, stable up to 80 degrees C and react s cleanly and rapidly with all amino groups of polypeptides. Several m odel peptides and two side chain-modified peptides sere sequentially d egraded using AITC and the cleavage reagent heptafluorobutyric acid (H FBA) up to seven amino acids from the N-terminus. Matrix-assisted lase r-desorption and ionization coupled with time-of-flight (MALDI-TOF) ma ss spectroscopy of the peptide mixture provided a clear ladder-like ma ss pro file with consecutive molecular ions corresponding to each shor tened peptide at picomole range. The results indicate the general util ity of this analytical protocol by the use of AITC as the amine-coupli ng reagent. (C) Munksgaard 1997.