Fractionation of peptides in protease digests of proteins by preparative isoelectric focusing in the absence of added ampholyte: A biocompatible and low-cost approach referred to as autofocusing

Peptides in the protease digests of some acidic and basic proteins in the range of 0.1-1.0% (w/v) could be fractionated with high reproducibility by a preparative isoelectric focusing on the basis of the amphoteric nature of samples in the absence of added carrier ampholytes. Enrichment of peptides of up to 15-fold could be achieved by the present method. This technique, referred to as autofocusing, did not require or yield any toxic solvents or solutes; thus, the present approach can be a low-cost and biocompatible method for peptide fractionation.