Ab initio quantum chemistry studies on the coding properties of cytosine derivatives generated by hydroxyl radical in aerobic conditions

The coding properties of four free radicals derived cytosine modifications were characterised by ab initio quantum chemistry method. The dimers geomet ry was optimised without any restrictions. The analysis was focused on the pairs consisting of a standard DNA base and one of the following cytosine d erivatives: 5,6-dihydroxycytosine (1); 5,6-dihydroxyuracil (2); uracil glyc ol (3); and isodialuric acid (4). The presented data allow to conclude that all studied derivatives are able to form the most stable pairs with guanin e. However, other pairs are also possible. In non-polar conditions the 5,6- dihydroxycytosine (1) pair with cytosine in addition to a normal pairing wi th guanine. This may stand for C double right arrow G transversion. The sig nificant impact of the environment polarity on the dimers stabilisation ene rgy was observed. The potential mispairing is enriched in the polar conditi ons The 5,6-dihydroxyuracil (2) and isodialuric acid (4) may form stable pa irs also with adenine. This may lead to C double right arrow T transition. The mispairing of uracil glycol (3) was found as insignificant. (C) 1999 El sevier Science B.V. All rights reserved.