Charge derivatization of peptides to simplify their sequencing with an iontrap mass spectrometer

The low energy collision-induced dissociation of fixed-charge derivatives [ tris(2,4,6-trimethoxyphenyl)phosphonium] of peptides was investigated using an electrospray ion trap mass spectrometer, The fixed charge directed the fragmentation pattern and generated solely N-terminal fragments with minima l internal rearrangement, regardless of the presence and position of basic amino acids in the peptide chain. Generally only b-type ions, accompanied b y less intense a-type ions, were observed, depending on the collision energ y. It was observed that the fixed charge controlled the fragmentation beyon d typical MS/MS, and thus the capacity of the ion trap to perform multiple stage fragmentation (MSn) was found particularly useful for obtaining the c omplete sequence information of the peptides, Copyright (C) 1999 John Wiley & Sons, Ltd.