In the present work, screen-printed electrodes (SPE) modified with a synthetic surfactant, didodecyldimethylammonium bromide (DDAB) and streptolysin O (SLO) were prepared for cytochrome P450 3A4 (CYP3A4) immobilization, direct non-catalytic and catalytic electrochemistry. The immobilized CYP3A4 demonstrated a pair of redox peaks with a formal potential of −0.325 ± 0.024 V (vs. the Ag/AgCl reference electrode). The electron transfer process showed a surface-controlled mechanism (“protein film voltammetry”) with an electron transfer rate constant (ks) of 0.203 ± 0.038 s−1. Electrochemical CYP3A4-mediated reaction of N-demethylation of erythromycin was explored with the following parameters: an applied potential of −0.5 V and a duration time of 20 min. The system with DDAB/SLO as the electrode modifier showed conversion of erythromycin with an efficiency higher than the electrode modified with DDAB only. Confining CYP3A4 inside the protein frame of SLO accelerated the enzymatic reaction. The increases in product formation in the reaction of the electrochemical N-demethylation of erythromycin for SPE/DDAB/CYP3A4 and SPE/DDAB/SLO/CYP3A4 were equal to 100 ± 22% and 297 ± 7%, respectively. As revealed by AFM images, the SPE/DDAB/SLO possessed a more developed surface with protein cavities in comparison with SPE/DDAB for the effective immobilization of the CYP3A4 enzyme.
The opportunistic fungus Candida krusei is the causative agent of nosocomial infections characterized by high mortality and development of resistance to drugs of the azole class. Therefore, develjoment of non-azole antifungal agents against resistant fungal strains is extremly important. Lanosterol 14-alpha demethylase (CYP51) is a well-known antifungal target. The optical SPR biosensor is a universal tool for screening studies in search of new drug prototypes. This paper presents the methodological aspects of high-hroughput SPR based screening of a library of low molecular weight compounds of natural origin for their interaction with C. krusei CYP51. It has been shown that when performing high-throughput screening, a researcher should pay special attention to the degree of a sensorgram curvature in the association phase. The described approaches to the analysis of high throughput screening data can be useful for researchers working with SPR biosensors from various manufacturers.
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