NP [PE]

Recently, we proposed a novel and effective strategy for enzyme immobilization, namely, as elastin-like polypeptide (ELP)-mediated silicification-based protein self-immobilization (ESPSI). Here, an enzyme with an acidic isoelectric point (pI) was chosen to further demonstrate the feasibility and generality of this method; pI is a critical factor in biosilicification. The lichenase (BglS) from Bacillus subtilis 168, with a theoretical pI of 5.77, was genetically fused to the cationic ELP. The recombinant chimera protein BglS-ELP (B-E) was purified through ELP-based nonchromatographic inverse transition cycling (ITC) method. B-E then was self-encapsulated within silica nanoparticle (NP) via ELP-mediated biomimetic silicification, producing the nanobiocatalyst B-E@silica. Excellent encapsulation efficiency (>85%) could be achieved within a short immobilization time (10 min). In addition, the encapsulation efficiency could be promoted through temperature-induced phase transition. Meanwhile, this method gave negligible protein leakage (<0.5%). Thus, the B-Epsilica showed good reusability, retaining similar to 80% of the initial activity after 10 reaction cycles. These results indicated that ESPSI was suitable for the protein with an acidic pI. In addition, phase transition was a unique route to improve immobilization efficiency.

A new method was developed for the determination of 2-nitrophenol (2-NP) by differential pulse voltammetry (DPV) employing the anodic oxidation of the present hydroxyl group using a non-traditional carbon film composite electrode (CFCE) based on a microcrystalline natural graphite-polystyrene composite film. Britton-Robinson (BR) buffer of pH 6.0 was found to be an optimal supporting electrolyte. Cleaning regeneration potentials E-in = +1300 mV and E-fin = 0 mV had to be applied before each measurement to get rid of problems connected with electrode passivation. Linear calibration curves were obtained in the concentration range from 0.2 to 10 mu mol L-1 of 2-NP for both tested matrices (deionized and drinking water). Limit of quantification (LOQ) for DPV at the CFCE was found to be 0.2 mu mol L-1 and 0.1 mu mol L-1 for deionized and drinking water, respectively.