On the reported solubilization of carcinogenic hydrocarbons in aqueous solutions of DNA

Abstract

Boyland & Green (1962 b ) , as well as Liquori, DeLerma, Ascoli, Botre & Trasciatti (1962) , have reported the solubilization of 3,4-benzpyrene and related compounds by dilute solutions of DNA and the former authors have interpreted their results as providing evidence for the intercalation of the planar hydrocarbon between the base pairs in the double helical molecule of DNA. These workers ground solid hydrocarbon with dilute aqueous solutions of DNA and measured the absorption spectrum of the supernatant solution from a centrifugation (Boyland & Green) or of a filtrate through a sintered glass filter (Liquori et al. ), and concluded that this was a measure of the solubilization of the hydrocarbons by DNA. We have shown clearly that under these conditions an aqueous colloidal suspension of the hydrocarbon is formed that can be sedimented completely with high-speed centrifugation or filtered completely by Millipore niters of uniform pore size. The only role the DNA plays in this phenomenon is to stabilize the colloid to some extent. This effect can be duplicated with the use of soap instead of DNA. Thus the above cited evidence for the in vitro , non-enzymic interaction of carcinogenic hydrocarbons with DNA, and the interpretation of intercalation, are invalid.