Use of capillary isotachophoresis to measure the degree of chemical substitution of dog serum albumin.

Analytical capillary isotachophoresis may provide a means for the rapid determination of the degree of substitution of proteins. Dog albumin conjugates with trinitrophenyl (TNP), fluorescein isothiocyanate (FITC) or monomethoxy polyethylene glycol (mPEG) have been studied as models for protein modification. An increase in the degree of covalent substitution of dog albumin with TNP, FITC or mPEG could be monitored rapidly using the UV signal or the conductivity signal as a measure of the increased protein zone width. These findings are encouraging with regard to the possible use of capillary isotachophoresis for screening the extent of protein modification.