The Protein Man's Blog | A Discussion of Protein Research

Salt precipitation can be a very powerful tool to purify proteins by precipitation. Ammonium sulfate is usually the salt of choice since it is cheap, very soluble in water, and is able to become much more hydrated (interacts with more water molecules) than almost any other ionic solvent. In practice, ammonium sulfate is either added directly as a solid or added as a (usually) saturated solution to precipitate desired proteins.

Immunoaffinity purification utilizes the unique high specificity of purified antibodies (polyclonal and monoclonal) immobilized onto a solid matrix (porous agarose beads) to rapidly and selectively purify target analytes from a complex mixture. Optimal elution conditions allow for the efficient purification of an active analyte while still allowing later regeneration of the immobilized antibodies.

ImmunoPrecipitation (IP) is a very useful immunochemical technique for isolating and purifying target proteins out of a complex sample (lysate). In conjunction with western blotting and/or other assay techniques, IPs can be used to determine: the presence and quantity of a protein; molecular weight of a polypeptide; rate of synthesis or degradation; enzymatic activity; and to identify certain post-translational modifications and interactions with other proteins, nucleic acids and ligands. There are different IP strategies to purify and analyze your target protein. Read on to see what IP strategy is perfect for you.

While agarose beads have been traditionally used for immunoprecipitation (IP) and other micro-scale protein and antibody purification procedures, magnetic beads have since taken lead and are now considered tool for protein immunoprecipitation.