Reaction of 1-n-propyl-1-nitrosourea with DNA in vitro

Abstract

[ n -propyl-2,3- ³ H]1- n -Propyl-1-nitrosourea (PNU) (sp. act.: 665 mCi/mmol) was synthesized and incubated with calf thy-mus DNA at pH 7.0 and 37°C in vitro . The degree of alkylation was proportional to the concentration of PNU added. The extent was 68 pmol/mg of DNA at 1 mM PNU. After mild add hydrolysis, purine bases were separated by Sephadex G-10 column chromatography. Although O ⁶ - n -propylguanine and O ⁶ - iso -propylguanine were separated by this method, 7- n -propylguanine and 7- iso -propylguanine were not separated. Then we used a h.p.l.c. equipped with a μBonda-pak-C ₁₈ reverse phase column with a linear gradient elution. 7- n -Propylguanine and O ⁶ - n -propylguanine were identified as major reaction products, and 7- iso -opropylguanine and O ⁶ - iso -propylguanine were identified as minor reaction products. The ratio of O ⁶ - n - and iso-propylguanine/7- n - and iso -propylguanines was 0.73. This ratio is similar to that produced by 1-ethyl-1-nitrosourea and 1- n -butyl-1-nitrosourea.