|dc.description.abstract||Enzyme immobilization for enzymatic synthesis is commonly used for stabilizing enzymes and improving their functions. A popular methodology is the physical adsorption of enzymes on nanoscaled carriers because their large surface area allows a high loading efficiency. Some enzymes have disordered structure (intrinsically disordered protein, IDP), and for simplicity we represent these as polyelectrolytes. The chosen nanocarrier is a halloysite nanotube, which is a clay mineral that possesses a tubular structure with oppositely charged surfaces.
In this work, we have used Monte Carlo simulations and a coarse-grained model to study the adsorption and conformation characteristics of an enzyme onto a halloysite nanotube. The enzyme is described as charged beads linked by harmonic bonds (polyelectrolyte). The nanotube is depicted by two types of beads constituting a positively charged inner surface and a negatively charged outer surface, and degree of ionization of surfaces is dependent on the pH. Here, we perform variation of pH and polyelectrolyte architecture. Titration curve of simulated nanotube is demonstrated to have pH-dependent characteristics. Contact probability of the polyelectrolyte in the interior of the tube shows different features from adsorption outside of the tube. Radius of gyration of the polyelectrolyte are analyzed by variations in pH and achitecture factors along the polyelectrolyte. The results demonstrate that the studied values of pH ranging from 2 to 8 affect the radius of gyration of the homogeneous polyelectrolyte, and the absolute value of net charge, the number of blocks, and the core block ratio have a significant correlation with condensation of the polyelectrolyte by statistical analysis. pH shows a significant correlation with an indicator of adsorption onto the inner surface.||