STYRENE OXIDE DNA-ADDUCTS - IN-VITRO REACTION AND SENSITIVE DETECTIONOF MODIFIED OLIGONUCLEOTIDES USING CAPILLARY ZONE ELECTROPHORESIS INTERFACED TO ELECTROSPRAY MASS-SPECTROMETRY

Styrene is one of the most important synthetic chemicals in the world and is subject to investigations concerning carcinogenicity and mutage nicity due to the active metabolite, styrene-7,8-oxide. This epoxide s hows a tendency to react, among others, with DNA and DNA constituents. The in vitro reaction of styrene oxide with DNA was investigated by c leaving incubated calf thymus DNA with two different enzymes, namely B enzonase and alkaline phosphatase, to obtain oligonucleotides of the t ype n-nucleotide-(n - 1)-phosphate with chain length from 2 to 8 bases . Alkylated and nonalkylated nucleotides were separated in groups acco rding to their chain length using capillary zone electrophoresis and w ere detected with electrospray mass spectrometry. This improvement in sensitivity made it possible to obtain new information about the react ion of styrene oxide with DNA, especially to detect unknown reaction p roducts. The results indicate that primarily purine bases were alkylat ed by styrene oxide before pyrimidine bases, which react with higher c oncentrations of styrene oxide. This means that in addition to the alr eady reported adducts in DNA at the N-7-, O-6- and N-2-position of gua nine also adducts at the nucleophilic sites of adenine can be found us ing mass spectrometry. We anticipate for the future this procedure wil l allow us to investigate base sequence specific reactions as well as interactions from xenobiotics and cytostatic drugs, since reaction pro ducts would directly be detectable.