THE AFFINITY TECHNOLOGY IN DOWNSTREAM PROCESSING

The quality criteria imposed on several biochemicals are stringent, th us, high-separation purification technology is important to downstream processing. Affinity-based purification technologies are regarded as the finest available, and each one differs in its purifying ability, e conomy, processing speed and capacity. The most widely used affinity t echnology is classical affinity chromatography, however, other chromat ography-based approaches have also been developed, for example, perfus ion affinity chromatography, hyperdiffusionTM affinity chromatography, high-perfor mance affinity chromatography, centrifugal affinity chrom atography, affinity repulsion chromatography, heterobifunctional ligan d affinity chromatography and the various chromatographic applications of 'affinity tails'. On the other hand, non-chromatographic affinity technologies aim at high throughput and seek to circumvent problems as sociated with diffusion limitations experienced with most chromatograp hic packings. Continuous affinity recycle extraction, aqueous two-phas e affinity partitioning, membrane affinity filtration, affinity cross- flow ultrafiltration, reversible soluble affinity polymer separation a nd affinity precipitation are all non-chromatographic technologies. Se veral types of affinity ligands are used to different extents; antibod ies and their fragments, receptors and their binding substances, avidi n/biotin systems, textile and biomimetic dyes, (oligo)peptides, antise nse peptides, cheIated metal cations, lectins and phenylboronates, pro tein A and G, calmodulin, DNA, sequence-specific DNA, (oligo)nudeotide s and heparin. Likewise, there are several support types developed and used; natural, synthetic, inorganic and composite materials.