Direct evidence for interaction between lead ions and kidney DNA from silver crucian carp

A direct interaction of lead (Pb) with kidney DNA from silver crucian carp (Carassius auratus gibelio) has been systematically studied in vitro using multi-techniques, including UV-vis absorption, extended X-ray absorption fine structure, vacuum ultraviolet circular dichroism spectral methods and gel electrophoresis. We find that Pb is bound with four oxygen or nitrogen atoms of DNA in its fresh shell at the distances of 2.64 A. Additionally, Pb may bind to the oxygen atom of nucleic acid or nitrogen atom of base pairs of DNA in that obvious changes in the secondary structure of DNA are found after Pb treatment. However, this direct interaction of Pb with DNA do not cause DNA cleavage in vitro.