Interaction of 2-Amino-1, 4-naphthoquinone Imine with Nucleic Acid

Abstract

On 2-amino-1, 4-naphthoquinone imine-HCl (ANQI), which had previously been reported to interact with nucleic acid and to inhibit the synthesis of nucleic acid and protein, especially of DNA, in Ehrlich mouse ascites tumor cells in vitro, the details of the interaction with nucleic acid were investigated by the methods of melting experiment for DNA, difference spectrum, equilibrium dialysis, and flow dichroism. The results are as follows : 1. The sites in DNA for attachment of ANQI were the purine base moieties, i.e., both of adenine and guanine. ANQI interacted with a highly polymerized native DNA at the highest degree and hardly interacted with such monomers as bases, nucleosides, and nucleotides. 2. ANQI was found to be able to bind to calf thymus DNA up to the ratio of 2 moles per 4 nucleotides by the method of equilibrium dialysis. This means that ANQI can attach with all the purine bases in DNA. 3. Such bivalent metal ions as Mg²⁺, Ca²⁺, Mn²⁺, Cu²⁺, Zn²⁺, and Ba²⁺ interfered with the interaction between ANQI and DNA. On the other hand, Hg²⁺ increased the extent of interaction. 4. It was found from the measurement of flow dichroism on DNA-bound ANQI that the orientation of ANQI was nearly parallel with the planes of DNA bases.