Hypochlorite-Modified LDL Induces Arrhythmia and Contractile Dysfunction in Cardiomyocytes

A Photoelectrochemical Sensor for the Detection of Hypochlorous Acid with a Phenothiazine-Based Photosensitizer

This paper presents the development of a photoelectrochemical sensor for hypochlorous acid (HOCl) detection, employing a phenothiazine-based organic photosensitizer (Dye-PZ). The designed probe, Dye-PZ, follows a D-π-A structure with phenothiazine as the electron-donating group and a cyano-substituted pyridine unit as the electron-accepting group. A specific reaction of the phenothiazine sulfur atom with HOCl enables selective recognition. The covalent immobilization of Dye-PZ onto a titanium dioxide nanorod-coated fluorine-doped tin oxide electrode (FTO/TiO2) using bromo-silane coupling agent (BrPTMS) resulted in the fabrication of the photoanode FTO/TiO2/BrPTMS/Dye-PZ. The photoanode exhibited a significant photoresponse under visible-light irradiation, with a subsequent reduction in photocurrent upon reaction with HOCl. The oxidation of the phenothiazine sulfur atom to a sulfoxide diminished the internal charge transfer (ICT) effect. Leveraging this principle, the successful photoelectrochemical sensing of HOCl was achieved. The sensor showed high stability, excellent reproducibility, and selective sensitivity for HOCl detection. Our study provides a novel approach for the development of efficient photoelectrochemical sensors based on organic photosensitizers, with promising applications in water quality monitoring and biosensing.

Halogenation Activity of Mammalian Heme Peroxidases

Mammalian heme peroxidases are fascinating due to their unique peculiarity of oxidizing (pseudo)halides under physiologically relevant conditions. These proteins are able either to incorporate oxidized halides into substrates adjacent to the active site or to generate different oxidized (pseudo)halogenated species, which can take part in multiple (pseudo)halogenation and oxidation reactions with cell and tissue constituents. The present article reviews basic biochemical and redox mechanisms of (pseudo)halogenation activity as well as the physiological role of heme peroxidases. Thyroid peroxidase and peroxidasin are key enzymes for thyroid hormone synthesis and the formation of functional cross-links in collagen IV during basement membrane formation. Special attention is directed to the properties, enzymatic mechanisms, and resulting (pseudo)halogenated products of the immunologically relevant proteins such as myeloperoxidase, eosinophil peroxidase, and lactoperoxidase. The potential role of the (pseudo)halogenated products (hypochlorous acid, hypobromous acid, hypothiocyanite, and cyanate) of these three heme peroxidases is further discussed.