Identification of the modifying sites of mono-PEGylated salmon calcitoninsby capillary electrophoresis and MALDI-TOF mass spectrometry

A capillary electrophoretic method (CE) was developed for the determination of the PEG-modification sites of three positional isomers of mono-PEG modi fied salmon calcitonins (mono-PEG-sCTs). Resistance to proteolytic degradat ion on the PEG modification sites resulted in different patterns of CE elec tropherograms for the tryptic digested mono-PEG-sCTs isomers, and the PEG m odification sites were assigned accordingly. The PEG-modification sites wer e also confirmed directly by determining the molecular masses of the trypti c digested PEG-modified fragments of respective mono-PEG-sCT by the matrix- assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectr ometry. (C) 2001 Elsevier Science B.V. All rights reserved.