Studies on Affinity Precipitation of Biomolecules Using Stimuli Sensitive Polymers Introduction Interactions between biomolecules and ligands play a critical role in medicine and biotechnology. Recovery of biomolecules in the pure form from a natural source and / or synthesized by a biotransformation route involves multiple steps and processes such as centrifugation, extraction, affinity chromatography and affinity ultrafiltration. Affinity based techniques are attractive as they provide higher selectivity and specificity and have emerged as an efficient bioseparation strategy for enzymes [Sii et al (1991)] and proteins [Senstad et al (1989)]. Affinity precipitation is a convenient bioseparation technique as it eliminates most of the drawbacks associated with affinity chromatography methods. Moreover, it offers ease of scale up, concentration and purification. The technique can be made into continuous operation process and the ligand used can be recycled. Affinity precipitation method usually consist of hetero bifunctional ligands coupled to the stimuli sensitive polymers e.g. poly N-isopropyl acrylamide (NIPA).