A U.S. Patent for “Purification of Proteins” was awarded to MilliporeSigma on March 19th, 2019. The present invention relates to a selectively soluble polymer capable of binding to a desired molecule in an unclarified mixture containing various biological materials and the methods of using such a polymer to purify a molecule from such a mixture. The polymer is soluble in the mixture under a certain set of process conditions such as pH or temperature and/or salt concentration and is rendered insoluble and precipitates out of solution upon a change in the process conditions. The polymer is capable of binding to the desired molecule (protein, polypeptide, etc). Learn More