ABSTRACT
The aim of protein purification is to isolate one particular protein from all the others in the starting material. A combination of fractionation techniques is used that exploits the solubility, size, charge, hydrophobicity or/and specific binding affinity of the protein of interest. Proteins differ in their cellular and tissue distribution, and thus if a protein is known to be abundant in one particular tissue it makes sense to start the purification from this source. Throughout the purification procedure, steps have to be taken to ensure that the protein of interest is not inactivated or denatured either by physical or biological factors. A suitable means of detecting the protein must be available to monitor the success of each stage in the purification procedure. Proteins can be separated from small molecules by dialysis through a semi-permeable membrane such as cellophane. In ion exchange chromatography, proteins are separated on the basis of their overall charge.
