Fourier Transform Infrared Spectra of Calf Thymus DNA and its Reactions with the Anticancer Drug Cisplatin

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Abstract
Fourier transform infrared (FT-IR) spectra of deoxyribonucleic acid (DNA) and its reaction products with the anticancer drug cis-Pt(NH3)2Cl2, cis-diamminodichloroplatinum (abbreviated cisplatin) in water and heavy water solutions or gels have been obtained and studied. The mid-IR spectra show considerable changes in the carbonyl (C=0) region and weaker, but significant perturbations in the sugar-phosphate absorption region (PO2−, OPC and COP). The carbonyl bands at 1710 and 1686 cm−1 of the control DNA in H2O and D2O, respectively, disappear and shift to lower frequencies in the spectra of cisplatin + DNA with a r = Pt/P = 0.2. Furthermore, the sugar-phosphate band at 1054 cm−1 of the C—O stretching vibration of the ribose-phosphate bond is reduced in intensity and slightly shifted to higher frequencies, indicating a reorientation of the phosphate group. In addition, the P—O stretching vibration frequency at 970 cm−1 is reduced in intensity on interaction with the drug. These changes depend to some extent on the water content in the control DNA and in the cisplatin + DNA complex. The water molecules in DNA in the presence of cisplatin reorganize themselves. The attack of the platinum drug at the N7 site of the guanine molecule in DNA exerts an effect on the DNA structure through a modification of the water average configuration and its stabilizing effect on the secondary structure.