Interaction of Cystamine and Cystamine Derivatives with Nucleic Acids and Nucleoproteins

Abstract

The disulphides–cystamine, bis (2-guanidoethyl) disulphide (GED), dimethylcystamine, tetramethylcystamine, tetraethyl cystamine, cystine dimethyl ester and cystine diethyl ester–have been shown to interact with and become reversibly bound to calf thymus DNA, E. ccli RNA, and to calf-thymus and rat-liver nucleoproteins. The interaction with the free nucleic acids resulted in a greatly enhanced thermal stability (elevated transition mid-points) of the DNA and RNA, and the reaction with the nucleoproteins resulted in a precipitation of these macromolecules. The disulphides which stabilized the nucleic acids and precipitated the nucleoproteins were typical diamines. Their association with the nucleic acids and nucleoproteins proved to be analogous to the interaction of cadaverine and spermidine with DNA. Thiols and disulphides which did not behave as di-cations had consequently no effect. The affinity of nucleic acids for diaminodisulphides may be of consequence in the toxicity of these compounds, and possibly of importance in the radio-protective activity of certain thiols and disulphides.