Gels Mimicking Antibodies in Their Selective Recognition of Proteins and Its Potential Use for Protein Crystallization - Molecules: Nucleation, Aggregation and Crystallization - page 23

hemoglobin during the polymerization. The free radicals should react also
with the free amino acids if they react with the hemoglobin molecules,
and one should expect a weaker color of this “hemoglobin column” —
which, however, was not the case. The experiment indicates that the
proteins are not linked covalently to the gel matrix.
What conclusions can be drawn from the finding
that (bio-)affinity methods do not always give
the selectivity theoretically expected?
Selective interactions between different constituents in the living cell form
the basis for its function. This bio-recognition has been utilized also in non-
biological systems, for instance, in methods utilizing biosensors (Jakusch
et al. , 1999 ) and in bio-affinity chromatography (Porath, 1981). These arti-
ficial systems have been employed with success in many investigations in
biochemistry and related disciplines. However, the specificity is not always
as high as expected, the main reason being that the ligands (for instance,
enzyme substrates, antibodies) and the functional monomers used for
imprinting of small molecules (for instance, methacrylic acid) are charged
and/or non-polar, and therefore create beds that to a greater or lesser
extent also behave as conventional media for ion exchange and/or
hydrophobic interaction chromatography, i.e. the selectivity is lost because
having many strong bonds is often not compatible with high selectivity
(see below). The situation is of particular concern when electrostatic and
hydrophobic interactions occur at the same time since an increase in the
ionic strength of the eluent decreases the former type of interaction but
increases the latter (Hjertén, 1973). In such cases it may be impossible to
find a buffer concentration such that the adsorbed sample can be released.
Accordingly, there are reasons to investigate whether methods can be
designed in which ligands and functional monomers are omitted, i.e. methods
based solely on weak interactions with the (chromatographic) matrix. The
experiments described herein should be considered against this background.