Abstract: | The effects of inorganic mono- and divalent salts of different types on how the cation polyelectrolyte polyallylamine hydrochloride
(PAA) binds with the oligomer enzyme urease were studied. It was shown that in solutions of the monovalent salts NaCl, KCl,
and NH4Cl, polyelectrolyte-protein complexes formed by electrostatic interactions, which decreased monotonically as the salt concentrations
increased according to the classic law of statistical physics, correlating the Debye radius with the ionic strength of the
solution. In solutions of the divalent salts Na2SO4 and (NH4)2SO4, the efficiency of the formation of the polyelectrolyte-protein complexes changed abruptly (the enzyme was drastically activated)
at low salt concentrations (∼0.6–0.8 mM), which was not consistent with the classic theory of charge interactions in solutions
with different ionic strengths. Turbidimetric titration at different salt concentrations in the given range revealed a high
aggregative ability for sulfates and low ability for chlorides. It was concluded that the anomalies in the concentration dependence
of the enzyme activity and aggregative ability were related to the formation of stable bonds PAA to the divalent SO42− anion, which increased drastically when the ratio of anion concentration to the number of positively charged PAA monomers
in solution reached 1: 2. |