Complexation ability of tetrasulfosubstituted cobalt(II) phthalocyanine toward ORF3a protein of SARS-CoV-2 virus.

Complex formation processes of tetrasulfosubstituted cobalt(II) phthalocyanine with ORF3a accessory protein of SARS-CoV-2 coronavirus were studied. The interaction of ORF3a protein with SARS-CoV-2 virus with tetrasulfosubstituted cobalt(II) phthalocyanine affords a stable complex in which metallophthalocyanine exists in the monomeric form. The complex formation induces slight changes in the secondary structure of the protein by increasing the fraction of disordered fragments of the polypeptide chain. The photoirradiation of the complex of ORF3a protein of SARS-CoV-2 virus with tetrasulfosubstituted cobalt(II) phthalocyanine leads to the photooxidation of amino acid residues of the protein.

Interaction of tetrasubstituted cationic aluminum phthalocyanine with artificial and natural membranes.

A study of the properties of water-soluble tetrasubstituted cationic aluminum phthalocyanine (AlPcN(4)) revealed efficient binding of this photosensitizer to phospholipid membranes as compared with tetrasulfonated aluminum and zinc phthalocyanine complexes. This also manifested itself in enhanced photodynamic activity of AlPcN(4) as measured by the photosensitized damage of gramicidin channels in a planar bilayer lipid membrane. The largest difference in the photodynamic activity of cationic and anionic phthalocyanines was observed in a membrane containing negatively charged lipids, thereby pointing to significant contribution of electrostatic interactions to the binding of photosensitizers to a membrane. Fluoride anions suppressed the photodynamic activity and binding to membrane of both tetraanionic and tetracationic aluminum phthalocyanines, which supports our hypothesis that interaction of charged metallophthalocyanines with phospholipid membranes is mostly determined by coordination of the central metal atom with the phosphate group of lipid.

Role of electrostatics in the binding of charged metallophthalocyanines to neutral and charged phospholipid membranes.

Binding of the cationic tetra(tributylammoniomethyl)-substituted hydroxoaluminum phthalocyanine (AlPcN(4)) to bilayer lipid membranes was studied by fluorescence correlation spectroscopy (FCS) and intramembrane field compensation (IFC) methods. With neutral phosphatidylcholine membranes, AlPcN(4) appeared to bind more effectively than the negatively charged tetrasulfonated aluminum phthalocyanine (AlPcS(4)), which was attributed to the enhancement of the coordination interaction of aluminum with the phosphate moiety of phosphatidylcholine by the electric field created by positively charged groups of AlPcN(4). The inhibitory effect of fluoride ions on the membrane binding of both AlPcN(4) and AlPcS(4) supported the essential role of aluminum-phosphate coordination in the interaction of these phthalocyanines with phospholipids. The presence of negative or positive charges on the surface of lipid membranes modulated the binding of AlPcN(4) and AlPcS(4) in accord with the character (attraction or repulsion) of the electrostatic interaction, thus showing the significant contribution of the latter to the phthalocyanine adsorption on lipid bilayers. The data on the photodynamic activity of AlPcN(4) and AlPcS(4) as measured by sensitized photoinactivation of gramicidin channels in bilayer lipid membranes correlated well with the binding data obtained by FCS and IFC techniques. The reduced photodynamic activity of AlPcN(4) with neutral membranes violating this correlation was attributed to the concentration quenching of singlet excited states as proved by the data on the AlPcN(4) fluorescence quenching.