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A range of 5,15-diphenylporphyrins with symmetric and unsymmetric substitution patterns were subjected to osmium tetroxide-mediated dihydroxylations. The resulting chlorins and bacteriochlorins present an important group of compounds for studying structure-activity relationships of photodynamic sensitizers. The regioselectivity of the dihydroxylation of various 5,15-diphenylporphyrins with unsymmetrical substitution patterns was also examined. Both diphenylchlorin diol (DPC) and diphenylbacteriochlorin tetrol (DPBC) examples were converted into reactive isothiocyanates and conjugated with bovine serum albumin (BSA).

The binding interaction mechanism between 5-phenyl-10,15,20-tri-(4-pyridyl)-porphyrin (TriPyP) and bovine serum albumin (BSA) was investigated by the fluorescence method and presented in this paper. Based on the mechanism of fluorescence quenching of BSA caused by TriPyP, the binding constants between TriPyP and BSA were measured at different temperatures by fluorescence spectroscopy at pH 7.40. As the binding constants decreased with increasing temperature, the type of quenching between TriPyP and BSA was determined as static quenching. Based on the Förster theory of non-radiation energy transfer, the binding distance and energy transfer efficiency at 25 °C between TriPyP (acceptor of energy) and BSA (donor of energy) were obtained. The results confirmed that the interaction was similar to non-radiation energy transfer. According to the thermodynamic parameters, the main type of binding force between TriPyP and BSA could be deduced as electrostatic force. Using synchronous fluorescence spectra, the effect of TriPyP on conformation of BSA was studied, and the hydrophobicity in microenvironment was developed by TriPyP. All these experimental results and theoretical data clarified that TriPyP could bind to BSA and be effectively transported in the human body, which could be a useful guideline for further drug design.

The interaction of meso-tetra-($N$-methyl-3-pyridyl)bacteriochlorin tetra 4-methylbenzenesulfonate, meso-tetra-($N$-methyl-4-pyridyl)porphine tetraiodide and meso-tetra-($N$-methyl-3-pyridyl)porphine tetraiodide with protein was studied. The localization of macrocycles in the protein and their influence on the processes of protein aggregation were established. The aggregation process is initiated by the transition of alpha structures into beta folds, caused by the binding of porphyrins at the sites of protein IB and IIA. The complexes were irradiated with blue and green light. The data obtained showed that by varying the intensity of the light exposure, one can influence the shift of the aggregation equilibrium, obtaining predominantly monomeric or aggregated structures. Thus, photoexposure can be used as an alternative method of treating diseases caused by amyloidosis and for regulating the state of the protein in the pharmacological preparations.