Isoelectric point - physical characteristic of proteins
Each protein has a characteristic isoelectric point for which its ionisation is minimum. Such as amino acids, proteins, comprising charged groups and at the ends of the peptide chain, are amphoteric in nature. In strong acid solution, protein molecule agrees to a proton whereas in strong basic solution it loses a proton. The pH at which the protein molecule comprise no net charge is known as its isoelectric point. This property can be utilized to separate proteins from mixture through electrophoresis.