PARENT SESSION
Posters P3D Genomic, proteomic and related technologies. Abstracts (720-730)

Probing DNA and RNA structures in the presence of photosynthetic pigments. Haider-Ali Tajmir-Riahi^*,1, Amin Ahmed Ouameur¹, Stavroula Diamantoglou¹, ¹ University of Québec at Trois-Rivières, Trois-Rivières, Québec, Canada

ABSTRACT- Porphyrins and their metal derivatives are strong nucleic acids binders. Some of these compounds have been used for radiation sensitization therapy of cancer and are targeted to interact with cellular DNA. Chlorophyll (Chl) binds DNA via guanine N-7 atom (major groove) and the backbone phosphate group with overall binding constant of K_Chl = 1.70 x 10⁴ M^-1, whereas chlorophyllin (Chln) intercalates into A-T and G-C regions with K_Chln = 1.60 x 10⁴ M^-1. Stronger pigment-RNA bindings were observed with guanine and adenine N-7 sites and the backbone phosphate group and no intercalation with K_Chl = 1.95 x 10⁵ M^-1 and K_Chln = 1.61 x10⁵ M^-1 . The larger K values obtained for Chl-RNA and Chln-RNA complexes are attributed to the formation of more stable four-five or six-coordinate metal cation in the RNA adducts. Aggregation of pigment-RNA and pigment-DNA complexes occurs at high metalloporphyrin concentrations. A partial B to A conformational transition occurred for pigment-DNA complexes, while no secondary structural changes were observed upon pigment-RNA interaction, and RNA remains in the A-family structure in these pigment complexes. References: (1) Neault & Tajmir-Riahi, Biophys. J. 76, 2177 (1999). (2) Neault & Tajmir-Riahi, J. Phys. Chem. B. 102, 1610 (1998). (3) Ahmed-Ouameur, Marty, Neault & Tajmir-Riahi, Biopolymers in press (2004).

KEY WORDS: RNA, Chlorophyllin, DNA, Chlorophyll