Gels Mimicking Antibodies in Their Selective Recognition of Proteins and Its Potential Use for Protein Crystallization - Molecules: Nucleation, Aggregation and Crystallization - page 12

involves polymerization of appropriate monomers (for instance, acrylamide and
its derivatives) in the presence of the protein to be adsorbed specifically, granu-
lation of the gel formed, packing a column with the gel particles, washing the
column to remove the protein, and finally application of the sample for selective
adsorption of the protein present during the polymerization of the monomers.
The approach resembles that used for entrapment (immobilization) of proteins
for affinity chromatography and somewhat like that for molecular imprinting of
small molecules, with the distinct difference that the monomer composition is
quite different and thereby the binding mechanism. This mechanism is dis-
cussed, for instance, in terms of (i) a new classification system for chromato-
graphic beds based on the number of bonds between the solute and the matrix
and the strength of each bond, and (ii) “non-specific bonds” (these bonds are
often harmful in conventional chromatography, but we have used them to our
advantage). In this classification system, the selective recognition is character-
ized by a large number of weak bonds. Therefore, so-called functional
monomers are not used for the preparation of the gels because they are often
charged and, accordingly, give rise to strong electrostatic interactions, i.e. the
beds behave to some extent as ion exchangers or matrices for hydrophobic inter-
action chromatography. In most experiments we have used a polyacrylamide gel
with large pores to facilitate diffusion of proteins into and out of the gel gran-
ules. When used in chromatography, these soft gels (which can be used repeat-
edly) allow only rather low flow rates. This problem can be overcome by a new
approach to preparing the granules. Potential applications of the selective beds
are discussed, as well as future improvements. These beds can be synthesized for
selective adsorption also of bio-particles, for instance viruses and bacteria, and
in the form of monoliths (continuous beds).
Keywords: Affinity chromatography; artificial gel antibodies; entrapment;
molecular imprinting; recognition of proteins; selectivity.
Introduction
More than a decade ago we described briefly a technique for selective
adsorption of a protein (Liao et al ., 1996). The method is based on the
preparation of a gel (for instance, crosslinked polyacrylamide) in the pres-
ence of the protein of interest, granulation of the gel, packing a chro-
matographic column with the granules, and finally removal of the
protein. Upon application of a sample containing this protein and other