Structural Analysis of DNA Interactions with Magnesium Ion Studied by Raman Spectroscopy

Problem statement: In the present study, FT Raman spectroscopy had been used to extend our knowledge about Magnesium ion - DNA interactions at various volume ratios (1:50, 1:20, 1:10 and 1:5). Approach: The analysis of FT Raman data supported the existence of structural specificities in the interaction and also the stability of DNA secondary structure. Results: Results from the Raman spectra clearly indicate that the interaction of Magnesium ion with DNA is mainly through the phosphate groups of DNA with negligible change of the B-conformation of DNA at all the volume ratios studied. For example, band at 1079 cm^-1 is assigned to the symmetrical stretching vibration of the nucleic acid phosphodioxy (PO-₂) group. This band in the order 1079→ 1075→ 1070→ 1066→ 1063 cm^-1 at all Magnesium ion DNA concentrations studied. Similarly, Raman band at 845 cm^-1 due to antisymmetrical phosphodiester (O-P-O) stretching of DNA. Conclusion: Magnesium ion interaction with the DNA phosphate is weak in comparison to interactions with the bases. On the other hand, the Raman signature of B-DNA is largely unperturbed by magnesium ion, suggesting much weaker interactions.