(Steps 1, 2) stepwise deposition of poly electrolyte layers; (Step 3) Exposure of the enzyme to solutions of pH > …Yu et al. employed a similar approach to encapsulate CAT into polyelectrolytes, PAH and PSS respectively . They investigated the direct electron transfer behavior and electrocatalytic response of polyelectrolyte encapsulated CAT to H2O2 reduction. The polyelectrolyte encapsulated CAT displays 4.5 times higher electrocatalytic response to H2O2 than non-encapsulated and solubilized CAT. However, the relative increase in catalytic response at the former was not proportional to the amount of enzyme deposited, since the entire CAT molecules were not found in their electrocatalytic active site.
This might be due to the reason that the distance between the CAT molecules and the electrode surface gets significantly increased after polyelectrolyte encapsulation. Furthermore, they observed through their detailed studies that, with increases in precursor polyelectrolyte layer number, the current response to H2O2 decreased significantly, while the electrode response time increased. In contrast, implementation of fewer polyelectrolyte layers lead to sensitive and fast response in H2O2 determinations. This approach of encapsulating CAT micro crystals into polyelectrolyte layers for biosensing provides a versatile approach to prepare high enzyme content films with improved enzyme activities.2.2. Surfactant Modified Matrices for CAT ImmobilizationIn an alternative approach, Chen et al. attempted to immobilize CAT onto cationic surfactant, (didodecyldimethylammonium bromide, DDAB) liquid crystal films .
They revealed through their results that the electron transfer of CAT is greatly improved in the AV-951 presence of DDAB. The electron transfer rate constant (ks) was observed to be 3.0 �� 0.4 s?1. However, their circular dichroism (CD) results illustrated that the conformation of CAT gets slightly perturbed by the hydrophobic nature of DDAB (Figure 2). The CD spectrum of CAT exhibits a negative peak at 237 nm, whereas for CAT-DDAB film it was observed at 232 nm. The negative peak at 232 nm was regarded as the shift from 237 nm of CAT film alone.Figure 2.CD spectra of CAT (�� ��), DDAB (�C �C �C), CAT-DDAB (��) films. CAT was prepared in pH 6.1, 10 mM phosphate buffer solution (PBS) with 50 mmol: l KCl. Temperature: 25��C (reproduced with permission from …Gebica et al. also studied the interaction of th
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