Interaction of a tricationic meso-substituted porphyrin with guanine-containing polyribonucleotides of various structures

Interactions of porphyrins with DNA: A review focusing recent advances in chemical modifications on porphyrins as artificial nucleases

The advance of porphyrins as artificial nucleases along the years have developed a class of compounds having potential therapeutic applications. Being an extrovert of chemistry, a variety of chemical modifications have been done on porphyrin macrocycle in order to improve the spectroscopic properties and to adapt as artificial receptors that can recognize molecules. The last twenty years has witnessed broad research in the arena of porphyrin- DNA interactions and their evolution from simple to more complex entities. In this review, we summarize the recent advances in the porphyrin-based structural modifications, with a specific emphasis on various effects of porphyrin on DNA cleavage potency. We particularly detailed the nuclease activity of cationic and anionic porphyrins, porphyrin dimers and conjugates as well as heme proteins till the third generation porphyrins as artificial nucleases.

Cationic porphyrins as destabilizer of a G-quadruplex located at the promoter of human MYH7 β gene

G-quadruplex (GQ) architecture is adopted by guanine rich sequences, present throughout the eukaryotic genome including promoter locations and telomeric ends. The in vivo presence indicates their involvement and role in various biological processes. Various small ligands have been developed to interact and stabilize/destabilize G-quadruplex structures. Cationic porphyrins are among the most studied ligands, reported to bind and stabilize G-quadruplexes. Herein, we report the recognition and destabilization of a parallel G-quadruplex by porphyrins (TMPyP3 and TMPyP4). This G-quadruplex forming 23-nt G-rich sequence is in the promoter region of Human Myosin Heavy Chain β gene (MYH7β). Presence of various putative regulatory sequence elements (TATA Box, CCAAT, SP-1) located in the vicinity of this quadruplex motif, highlight its regulatory implications. Biophysical methods as Circular Dichroism Spectroscopy, UV-Absorption Spectroscopy, UV-Thermal Denaturation and Fluorescence Spectroscopy (steady as well as Time Resolved) have been used for studying the interaction and binding parameters. It is proposed that porphyrins have a destabilizing effect on the G-quadruplexes with parallel topology and a stronger binding specifically via intercalation mode is needed to cause destabilization. The study deals with better understanding and insights of DNA-Drug interactions in biological systems.Communicated by Ramaswamy H. Sarma.

Comparative study of binding interactions between porphyrin systems and aromatic compounds of biological importance by multiple spectroscopic techniques: A review

The specific spectroscopic and redox properties of porphyrins predestine them to fulfill the role of sensors during interacting with different biologically active substances. Monitoring of binding interactions in the systems porphyrin-biologically active compound is a key question not only in the field of physiological functions of living organisms, but also in environmental protection, notably in the light of the rapidly growing drug consumption and concurrently the production of drug effluents. Not always beneficial action of drugs on natural porphyrin systems induces to further studies, with commercially available porphyrins as the model systems. Therefore the binding process between several water-soluble porphyrins and a series of biologically active compounds (e.g. caffeine, guanine, theophylline, theobromine, xanthine, uric acid) has been studied in different aqueous solutions analyzing their absorption and steady-state fluorescence spectra, the porphyrin fluorescence lifetimes and their quantum yields. The magnitude of the binding and fluorescence quenching constants values for particular quenchers decreases in a series: uric acid > guanine > caffeine > theophylline > theobromine > xanthine. In all the systems studied there are characters of static quenching, as a consequence of the π-π-stacked non-covalent and non-fluorescent complexes formation between porphyrins and interacting compounds, accompanied simultaneously by the additional specific binding interactions. The porphyrin fluorescence quenching can be explain by the photoinduced intermolecular electron transfer from aromatic compound to the center of the porphyrin molecule, playing the role of the binding site. Presented results can be valuable for designing of new fluorescent porphyrin chemosensors or monitoring of drug traces in aqueous solutions. The obtained outcomes have also the toxicological and medical importance, providing insight into the interactions of the water-soluble porphyrins with biologically active substances.

Porphyrin-based cationic amphiphilic photosensitisers as potential anticancer, antimicrobial and immunosuppressive agents

Photodynamic therapy (PDT) combines a photosensitiser, light and molecular oxygen to induce oxidative stress that can be used to kill pathogens, cancer cells and other highly proliferative cells. There is a growing number of clinically approved photosensitisers and applications of PDT, whose main advantages include the possibility of selective targeting, localised action and stimulation of the immune responses. Further improvements and broader use of PDT could be accomplished by designing new photosensitisers with increased selectivity and bioavailability. Porphyrin-based photosensitisers with amphiphilic properties, bearing one or more positive charges, are an effective tool in PDT against cancers, microbial infections and, most recently, autoimmune skin disorders. The aim of the review is to present some of the recent examples of the applications and research that employ this specific group of photosensitisers. Furthermore, we will highlight the link between their structural characteristics and PDT efficiency, which will be helpful as guidelines for rational design and evaluation of new PSs.