Tuning Enzyme/α-Zr(IV) Phosphate Nanoplate Interactions via Chemical Modification of Glucose Oxidase

Abstract

Using glucose oxidase (GOx) and α-Zr(IV) phosphate nanoplates (α-ZrP) as a model system, a generally applicable approach to control enzyme–solid interactions via chemical modification of amino acid side chains of the enzyme is demonstrated. Net charge on GOx was systematically tuned by appending different amounts of polyamine to the protein surface to produce chemically modified GOx(n), where n is the net charge on the enzyme after the modification and ranged from −62 to +95 electrostatic units in the system. The binding of GOx(n) with α-ZrP nanosheets was studied by isothermal titration calorimetry (ITC) as well as by surface plasmon resonance (SPR) spectroscopy. Pristine GOx showed no affinity for the α-ZrP nanosheets, but GOx(n) where n ≥ −20 showed binding affinities exceeding (2.1 ± 0.6) × 106 M−1, resulting from the charge modification of the enzyme. A plot of GOx(n) charge vs Gibbs free energy of binding (ΔG) for n = +20 to n = +65 indicated an overall increase in favorable interaction between GOx(n) and α-ZrP nanosheets. However, ΔG is less dependent on the net charge for n > +45, as evidenced by the decrease in the slope as charge increased further. All modified enzyme samples and enzyme/α-ZrP complexes retained a significant amount of folding structure (examined by circular dichroism) as well as enzymatic activities. Thus, strong control over enzyme–nanosheet interactions via modulating the net charge of enzymes may find potential applications in biosensing and biocatalysis.

Polypyrrole-Based Nanorobots Powered by Light and Glucose for Pollutant Degradation in Water

“…Zeta potential measurements (Figure B) indicate that the typical positive surface charge of PPy particles is shifted to a negative value due to incorporation of PPy-COOH. The charge became even more negative after enzyme immobilization since the GOx and Cat are both acidic and their isoelectric points are located at pH = 4.3 and 5.4, respectively. − …”

Kinetic Study on Enzymatic Hydrolysis of Cellulose in an Open, Inhibition-Free System

“…SPR is based on the principles of total internal reflection, whereby light creates surface plasmons along a thin metal layer adjacent to immediate vicinity of the surface layer of a sensor chip. Adsorption of enzymes and the subsequent depolymerization of the cellulase film on a SPR sensor change the refractivity and lead to a shift of the SPR angle (e.g., the angle at which the reflected light intensity is at minimum). , The change in the SPR angle is monitored as a function of time and further analyzed for calculating the properties of the adsorbed layers. In a typical SPR experiment, degassed buffer solution without the enzyme was flowed into an SPR sensor chamber assembled with a cellulose-coated film onto the SPR gold chip.…”