A study of metalloporphyrin-polynucleotide interactions by microcalorimetry and circular dichroism

Minor groove binding of Co(III)meso-tetrakis(N-methylpyridinium-4-yl)porphyrin to various duplex and triplex polynucleotides

The binding site and the geometry of Co(III)meso-tetrakis(N-methylpyridinium-4-yl)porphyrin (CoTMPyP) complexed with double helical poly(dA).poly(dT) and poly(dG).poly(dC), and with triple helical poly(dA).[poly(dT)](2) and poly(dC).poly(dG).poly(dC)(+) were investigated by circular and linear dichroism (CD and LD). The appearance of monomeric positive CD at a low [porphyrin]/[DNA] ratio and bisignate CD at a high ratio of the CoTMPyP-poly(dA).poly(dT) complex is almost identical with its triplex counterpart. Similarity in the CD spectra was also observed for the CoTMPyP-poly(dG).poly(dC) and -poly(dC).poly(dG).poly(dC)(+) complex. This observation indicates that both monomeric binding and stacking of CoTMPyP to these polynucleotides occur at the minor groove. However, different binding geometry of CoTMPyP, when bind to AT- and GC-rich polynucleotide, was observed by LD spectrum. The difference in the binding geometry may be attributed to the difference in the interaction between polynucleotides and CoTMPyP: in the GC polynucleotide case, amine group protrude into the minor groove while it is not present in the AT polynucleotide.

Analytical Application of Oligopyrrole Macrocycles

Progress of modern analytical chemistry is closely related with advancement in other fields such as organic chemistry and biochemistry. Successful solution of current scientific problems is inconceivable without close cooperation of different chemical disciplines. As an example of such hot and very intricate theme research in the field of molecular recognition of biologically active compounds can serve, where numerous methods of analytical chemistry, organic chemistry and biochemistry can suitably be utilized, elaborated and brought into consonance. This multidisciplinary overlap logically leads to the advent of new scientific fields with their own tools, methodologies and subjects of exploration - bioanalytical chemistry and nanotechnology. This review covers different aspects of analytical application of oligopyrrole macrocycles (mainly porphyrins and sapphyrins). These compounds are widely used in analytical chemistry due to their outstanding optical properties. In our contribution oligopyrrole macrocycles are considered as signaling and structural parts of chemical receptors and selectors in various applications. Introduction of different moieties into meso-position of macrocyclic rings allows to obtain e.g., sterically well-organized receptors for recognition of biologically important analytes, new chromatographic materials, and powerful tools in electrochemical research. Finally, future trends in the field are outlined briefly.

DNA-drug interaction measurements using surface plasmon resonance

The interactions of the drugs 2,7-bis[(diethylamino)-ethoxy]-fluoren-9-one dihydrochloride (Tilorone), 2,7-bis[(dipropylamino)-acetamido]-fluoren-9-one dihydrochloride (FA-2), 2'-(4-hydroxyphenyl)-5-(4-methyl-1-piperazinyl)-2,5'-bi-1H-benzimidazole trihydrochloride (Hoechst 33258), and hematoporphyrin IX derivative (HPD) with synthetic self-complementary DNA (36-b.p.; 5'-biotin-spacer-[d(CGCTATATAGCG)]3-3') were studied by SPR (Surface Plasmon Resonance). Monolayers of biotinylated DNA were immobilized on a streptavidin-dextran-gold triple-layer. Small portions of the drugs (approximately 30 pmol/ml) were injected in continuous flow. The mass corresponded to the amount of the bound molecules. Injections of 50 mM sodium hydroxide pulses separated the DNA double strands, releasing the effector molecules. Subsequent treatments with the effectors gave reproducible results. The maximum interaction between drug and DNA was observed in the case of Tilorone. 41 molecules could bind to the 36-b.p. DNA duplex. To investigate the microscopic behavior in condensed nucleic acid phases, SFM (Scanning Force Microscopy)-imaging and polarizing microscopic observations of DNA-effector complexes were carried out. Supplementary UV-absorption thermal denaturation curves of DNA with the above-mentioned effectors in dilute solutions were measured. As an additional aid to understand the geometries of DNA-drug interactions, computer simulations were performed and compared with the experimental data.