The effects of Cu²⁺ and Pb²⁺ on the solution structure of calf thymus DNA: DNA condensation and denaturation studied by fourier transform IR difference spectroscopy

Abstract

The interaction of calf thymus DNA with Cu2+ and Pb2+ was studied in aqueous solution at pH 6.5 with metal/DNA (P) (P = phosphate) molar ratios (r) 1/80, 1/40, 1/20, 1/10, 1/4, 1/2, and 1, using Fourier Transform ir (FTIR) spectroscopy. Correlations between the ir spectral changes, metal ion binding mode, DNA condensation, and denaturation, as well as conformational features, were established. Spectroscopic evidence has shown that at low metal/DNA (P) molar ratios 1/80 and 1/40, copper and lead ions bind mainly to the PO2- of the backbone, resulting in increased base-stacking interaction and duplex stability. The major copper ion base binding via G-C base pairs begins at r > 1/40, while the lead ion base binding occurs at r > 1/20 with the A-T base pairs. The denaturation of DNA begins at r = 1/10 and continues up to r = 1/2 in the presence of copper ions, whereas a partial destabilization of the helical structure was observed for the lead ion at high metal ion concentration (r = 1/2). Metal-DNA binding also results in DNA condensation. No major departure from the B-family structure was observed, upon DNA interaction with these metal ions.

Utilization of DNA-metal Ion Biomatrix as a Relative Humidity Sensor

“…The increase of intensity based on the interaction with DNA and metal ion has been reported at the IR spectra in aqueous solution. 13,15,18 Additionally, the conformational change of DNA structure with the RH has been reported. [19][20][21] In this case, DNA structure changes from A-form to B-form with the increase of RH.…”

Does DNA acid fixation produce left‐handed Z structure?

“…A small increase in intensity is observed for several DNA in-plane vibrations at 1717 cm -~ (G,T), 1663 cm -~ (T,G,A,C), 1609 cm -1 (mainly A) and 1492 cm -~ (C,G) [15][16][17][18][19] in the difference spectra of acid-DNA complexes (Fig. 1, r = 1/40).…”

Structural organization of DNA–protein complexes of chromatin studied by vibrational and electronic circular dichroism

“…2). Based on the previously published results [1,3,5,6,10,12,16] it is possible to assign the major spectral features as summarized in the Table 1. Thus, IR/VCD spectra of large supramolecular complexes can be analyzed at higher protein to DNA ratios, unreachable for conventional UV-CD spectroscopy.…”