Page 20 - Subyek Encyclopedia - Encyclopedia of Separation Science

Sepsci*1*TSK*Venkatachala=BG
I / AFFINITY SEPARATION 15

Figure 10 Model of the Phe}Arg dipeptidyl substrate bound in the acitve site of porcine pancreatic kallikrein. The illustration shows
Asp189 at the bottom of the primary binding pocket as well as the side chains of Tyr99 and Try215, which form the secondary binding
pocket, with the phenyl ring of the Phe residue sandwiched between the hydrophobic side chains of these residues.

(DMFs) with the FDA. DMFs allows companies to standards and Good Manufacturing Practice (GMP)
use synthesized ligands for very high purity protein is an integral part of a DMF. Few researchers select-
pharmaceuticals with total conRdence. New Drug ing a speciRc medium consider the long-term implica-
Applications (NDA) and Investigational New Drugs tions of stability under depyrogenating conditions,
(IND) documents incorporating such stable afRn- the number of cycles that can be achieved (lifetime in
ity media can now be submitted to the FDA, safe in use), its availability in bulk, whether it is manufac-
the knowledge that all appropriate information is on tured under aseptic conditions and the price when
Rle. The effective guarantee of minimum quality supplied in bulk. If the researcher makes a good
initial selection, the research data produced can be
utilized in development phases with conRdence. ‘Fast
tracking’ is facilitated, with minimum aggravation,
maximum efRciency and minimum puriRcation
costs.

Alternative Af\nity Approaches

Aqueous two-phase systems have been extensively
applied to bimolecular puriRcations, by attaching af-
Rnity ligands to one of a pair of phase-forming poly-
mers, a method known as afTnity partitioning.
Although a substantial body of research literature is
available, few systems appear to have been adopted
for commercial purposes. Reactive dyes, with their
simple and well-deRned coupling chemistries, have
generally been favoured as the active ligand. The
Figure 11 Comparison of the structures of (A) the Phe}Arg
dipeptide, and (B) the ‘biomimetic’ ligand designed to bind at the advantage of afRnity partitioning is that the pro-
active site of the porcine pancreatic kallikrein. cess is less diffusion-controlled, binding capacities