An FTIR Spectroscopic Study of Calf-thymus DNA Complexation with Al(III) and Ga(III) Cations |
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| Authors: | R Ahmad M Naoui J F Neault S Diamantoglou H A Tajmir-Riahi |
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| Institution: | Departement Chimie-Biologie , Université du Québec à Trois-Rivières , C.P. 500, Trois-Rivières , Québec , Canada , G9A 5H7 |
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| Abstract: | Abstract The interaction of calf-thymus DNA with trivalent Al and Ga cations, in aqueous solution at pH =6–7 with cation/DNA(P) (P=phosphate) molar ratios (r) 1/80, 1/40, 1/20, 1/10, 1/4 and 1/2 was characterized by Fourier Transform infrared (FTIR) difference spectroscopy. Spectroscopic results show the formation of several types of cation-DNA complexes. At low metal ion concentration (r=l/80, 1/40), both cations bind mainly to the backbone PO2 group and the guanine N-7 site of the G-C base pairs (chelation). Evidence for cation chelate formation comes from major shifting and intensity increase of the phosphate antisymmetric stretch at 1222 cm-1 and the mainly guanine band at 1717 cm1. The perturbations of A-T base pairs occur at high cation concentration with major helix destabilization. Evidence for cation binding to A-T bases comes from major spectral changes of the bands at 1663 and 1609 cm-1 related mainly to the thymine and adenine in-plane vibrations. A major reduction of the B-DNA structure occurs in favor of A-DNA upon trivalent cation coordination. |
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