Sensitive radioimmunoassays for O6-n-butyldeoxyguanosine, O2-n-butylthymidine and O4-n-butylthymidine.

Radioimmunoassays have been developed using monoclonal antibodies from hybridomas raised against bovine serum albumin conjugates of O6-n-butylguanosine, O2-n-butylthymidine riboside and O4-n-butylthymidine riboside. The assays showed 50% inhibition of binding of specific (( 3H]butyl-deoxynucleosides by 0.044, 0.069 and 0.45 pmole of cold O6-n-butyldeoxyguanosine, O2-n-butylthymidine and O4-n-butylthymidine respectively, corresponding to affinity constants of 2.7 x 10(10), 1.1 x 10(10) and 8.8 x 10(8) respectively. In competitive radioimmunoassays a similar degree of inhibition required approximately 10(7)-fold higher concentrations of normal deoxynucleotides. From the relative inhibitions produced by a wide range of alkylated and normal nucleosides and bases we conclude that each antibody primarily recognises butylation, as compared to other alkylations, at the sites specified by the immunogen. The radioimmunoassays should be suitable for the detection of these potentially promutagenic lesions in digests of DNA exposed to low (biological) levels of butylation.