Prevention of La3+ on DNA Damage Caused by Hg2+ from Fish Intestines

The aim of this study was to investigate the effects of rare earth elements (REEs) in preventing Hg2+ pollution, using fish intestinal DNA in vitro and study the mechanism of the interactions between Hg2+, La3+, the mixture of La3+ and Hg2+ and DNA by spectroscopy. The interactions between Hg2+, La3+, the mixture of La3+ and Hg2- and DNA from fish intestine in vitro was investigate by using absorption spectrum and fluorescence emission spectrum. Ultraviolet absorption spectra indicated that the addition of Hg2+, La3+, and the mixture of La3+ and Hg2+ to DNA generated obvious hypochromic effect. Meanwhile, the 205.2 nm peak of DNA blue and the 258.2 nm peak of DNA red shifted. The hypochromic effect and peak shift was caused by these ions in an order of Hg2+ > Hg2+ + La3+ > La3-. The fluorescence emission spectra showed that as the addition of Hg2+, La3+, and the mixture of La3+ and Hg2+. the emission peak at about 416.2 nm of DNA did not obviously change, but the fluorescence intensity reduced gradually with the order in treatment was Hg2+ > Hg2+ + La3+ > La3+. Hg2+, La3+, and the mixture of La3+ and Hg2+ had 1.12, 0.58, and 0.81 binding sites to DNA, the fluorescence quenching of DNA caused by them all attributed to static quenching. The binding constants KA of binding sites were 3.82 × 104 and 4.22 × 102 L·mol−1; 2.50 × 104 and 2.95 × 103 L·mol−1; 3.05 × 104 and 1.00 × 103 L·mol−1. The results showed that La3+ could relieve destruction caused by Hg2+ on the DNA structure.