Flexibility of DNA and RNA upon Binding to Different Metal Cations. An Investigation of the B to A to Z Conformational Transition by Fourier Transform Infrared Spectroscopy

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Abstract
The interaction of DNA and RNA with Cu(II), Mg(II), [Co(NH3)6]3+ [Co(NH3)5Cl]2+ chlorides and, cis- and trans-Pt(NH3)2Cl2 (CIS-DDP, trans-DDP) has been studied by Fourier Transform Infrared (FT-IR) spectroscopy and a correlation between metal-base binding and conformational transitions in the sugar pucker has been established. It has been found that RNA did not change from A-form on complexation with metals, whereas DNA exhibited a B to Z transition. The marker bands for the A-form (C′3-endo-anti conformation) were found to be near 810–816 cm−1, while the bands at 825 and 690 cm−1 are marker bands for the B- conformation (C′2-endo, anti), The B to Z (C3′-endo, syn conformation) transition is characterized by the shift of the band at 825 cm−1 to 810–816 cm−1 and the shift of the guanine band at 690 cm−1 to about 600–624 cm−1.