Quercetin adsorption with imprinted polymeric materials.

In this study, molecularly imprinted polymer membranes were synthesized for the recognition and adsorption of quercetin. For this, quercetin imprinted polymeric membranes [p(HEMA-MAH)] (Poly(2-hydroxyethyl methacrylate-co-N-methacryloly-l-histidinemethylester) were synthesized by UV polymerization technique using HEMA and MAH as monomers. Synthesized polymeric membranes were characterized with SEM, FTIR and swelling test. Characterized membranes were used for the direct adsorption of quercetin in a batch system. Quercetin adsorption conditions were optimized by using the quercetin imprinted polymeric membrane by altering the pH, temperature and initial quercetin concentration of the adsorption medium. Effect of adsorption time was also studied for up to 180 min. The optimum pH and temperature was determined between 4.0 and 45 °C. Maximum adsorbed amount of quercetin onto quercetin imprinted poly(HEMA-MAH) membrane was found to be as 299.6 mg/g membrane using the initial quercetin concentration of 2.0 mg/ml. Adsorbed quercetin was desorbed from the polymeric membranes with isopropyl alcohol with desorption yield of 98.3%. and repeated usability of the quercetin imprinted polymeric membranes was fallowed for 7 adsorption/desorption cycles. At the end of the 7th reuse, quercetin adsorption capacity of the quercetin imprinted poly(HEMA-MAH) membranes decreased only about 10%.

Synthesis of urease hybrid nanoflowers and their enhanced catalytic properties.

Increasing numbers of materials have been extensively used as platforms for enzyme immobilization to enhance catalytic activity and stability. Although stability of enzyme was accomplished with immobilization approaches, activity of the most of the enzymes was declined after immobilization. Herein, we synthesize the flower shaped-hybrid nanomaterials called hybrid nanoflower (HNF) consisting of urease enzyme and copper ions (Cu(2+)) and report a mechanistic elucidation of enhancement in both activity and stability of the HNF. We demonstrated how experimental factors influence morphology of the HNF. We proved that the HNF (synthesized from 0.02mgmL(-1) urease in 10mM PBS (pH 7.4) at +4°C) exhibited the highest catalytic activity of ∼2000% and ∼4000% when stored at +4°C and RT, respectively compared to free urease. The highest stability was also achieved by this HNF by maintaining 96.3% and 90.28% of its initial activity within storage of 30 days at +4°C and RT, respectively. This dramatically enhanced activity is attributed to high surface area, nanoscale-entrapped urease and favorable urease conformation of the HNF. The exceptional catalytic activity and stability properties of HNF can be taken advantage of to use it in fields of biomedicine and chemistry.

Synthesis of copper ion incorporated horseradish peroxidase-based hybrid nanoflowers for enhanced catalytic activity and stability.

In this study, we report the preparation, catalytic activity and stability of a hybrid nanoflower (hNF) formed from horseradish peroxidase (HRP) enzyme and copper ions (Cu(2+)). We studied the morphology of hNFs as a function of the concentrations of copper (Cu(2+)) ions, chloride ions (Cl(-)) and HRP enzyme, the pH of the buffer solution (phosphate buffered saline), and the temperature of the reaction. The effects of morphology on the catalytic activity and stability of hNFs were evaluated by oxidation of guaiacol (2-methoxyphenol) to colored 3,3-dimethoxy-4,4-diphenoquinone in the presence of hydrogen peroxide (H2O2). The enhanced activity of hNFs synthesized (from 0.02 mg mL(-1) HRP in 10 mM PBS (pH 7.4) at +4 °C) was 17 595 U mg(-1), which was ∼300% higher than free HRP in PBS, where it achieved an activity of 5952 U mg(-1). In terms of stability, these hNFs stored in PBS buffer at +4 °C and room temperature (RT = 20 °C) lost 4% and 20%, respectively, of their initial catalytic activities within 30 days. Finally, we demonstrated that these hNFs can be utilized as sensors for the detection of dopamine.

Purification of peroxidase from red cabbage (Brassica oleracea var. capitata f. rubra) by affinity chromatography.

Peroxidase was purified in a single step using 4-amino benzohydrazide affinity chromatography from red cabbage (Brassica oleracea var. capitata f. rubra), and some important biochemical characteristics of the purified enzyme were determined. The enzyme, with a specific activity of 3,550 EU/mg protein, was purified 120.6-fold with a yield of 2.9% from the synthesized affinity matrix. The molecular weight of the enzyme was found to be 69.3 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The enzyme exhibited maximum activity at pH 7.0 and 30 °C. For guaiacol substrate, the K m and V max values were found as 0.048 mM and 1.46 EU/mL/min, respectively. Additionally, the IC50 and K i values for 4-amino benzohydrazide were calculated to be 1.047 and 0.702±0.05 mM, respectively, and 4-amino benzohydrazide showed noncompetitive inhibition.