[Incapsulation of enzymes into polyelectrolyte nano- and microcapsules and the problem of the development of enzymatic microdiagnostics].

The incapsulation of proteins into polyelectrolyte microcapsules (PE-microcapsules) has been studied with the aim to develop microdiagnostica for the presence of low-molecular-weight compounds in native biological fluids. The problem was solved using two enzymes: lactate dehydrogenase and urease. Polyelectrolyte microcapsules were prepared using two polyanions: polystyrene sulfonate (PSS) and dextran sulfate (DS), and two polycations: polyallylamine (PAA) and polydiallylmethylammonium (PDADMA). CaCO3 microspherulites with the incapsulated enzyme served as a "core" in the formation of polyelectrolyte microcapsules. It was shown that the main problem in the preparation of a polyelectrolyte microdiagnosticum is the selection of an oppositely charged pair of polyelectrolytes optimal for the active functioning of the enzyme. It follows from the results obtained that the best polyelectrolyte pairs for the formation of the envelope of a PE-microcapsule are PAA/DS and PAA/PSS for lactate dehydrogenase and PSS/PDADMA for urease. Taking into account these data, we designed enzyme-containing microcapsules with different polyelectrolyte compositions and different numbers of layers and studied their properties.

[The electrostatic contribution to interactions of some enzymes with polyelectrolytes].

To explain the inhibitory action of polyelectrolytes on enzymes and, in particular, to define potentially reactive zones for the binding of polyelectrolyte, the electric potential of enzymes lactate dehydrogenase and glutamate dehydrogenase was calculated using the solution of the Poisson-Boltzmann equation by a numerical method with the use of the Gauss-Seidel relaxation method at three pH values: 6.5, 7.0, and 8.0 and three values of ionic strength: 50, 100, and 150 mm. On the basis of these calculations and their visualization, representative sites for favorable binding of polyanions were determined as extended areas on the surface of proteins with the positive potential in the neutral pH region. It was shown that there is a correlation between the area of positive potential and the efficiency of enzyme inactivation for a number of pH values and concentrations of salt for two enzymes. The calculations performed allowed one to explain the inhibitory action of polyelectrolytes on the specified enzymes to understand the difference between the values of polyelectrolyte inactivation constants for the two enzymes and estimate the minimal areas of the positive potential on the protein surface that provide their effective inhibition.