The effect of Cd ions on salmon sperm DNA was studied by means of circular dichroism(CD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and fluorescence spectroscopy. The CD spectral and fluorescent probe-acriflavine results indicate that the DNA underwent a conformation change upon the addition of Cd ions. XPS and Raman studies reveal that there existed interactions between Cd ions and the phosphate groups of the DNA. In addition, a new band appeared at 803 cm -1in the Raman spectra, which can be attributed to characterizing "marker" band of A-DNA. It is concluded that Cd ions can be coordinated by the phosphate groups of the DNA and induce the conformation changes of the DNA from B-DNA to A-DNA.
CdS nanoparticles were synthesized by using two complementary 2′ phosphorothioate oligo DNA, oligoG 10 SH and oligoC 10 SH as stabalizers. Because the thiol group was modified at phosphate site between C1 and C2 of 5′ end, the spatial exposure of DNA residue at C1 site was preponderant compating with the spatial exposure of the nanoparticles when the DNA renatured. The experimental result showed DNA renaturation ratio is about 50% and CdS nanoparticles were assembled into parallel quadrilateral array as the DNA renaturation progressed.
