A theoretical study of the cis-syn pyrimidine dimers in the gas phase and water cluster and a tautomer-bypass mechanism for the origin of UV-induced mutations
Vi. Danilov et al., A theoretical study of the cis-syn pyrimidine dimers in the gas phase and water cluster and a tautomer-bypass mechanism for the origin of UV-induced mutations, J BIO STRUC, 19(1), 2001, pp. 179-191
A quantum mechanical study of all cis-syn cyclobutane pyrimidine photodimer
s including the normal and rare tautomeric forms of bases has been performe
d using the ab initio method at HF/6-31G(d,p), MP2(fc)//HF/6-31G(d.p) and M
P2(fc)/6-31G(d,p) levels. A puckering angle of the cyclobutyl ring and twis
t angle of pyrimidine rings with respect to each other is well described by
these calculations. It is predicted that in the gas phase all photodimers
containing the rare imino form of cytosine are more stable than those conta
ining its normal form. The Monte Carlo simulations show that the dimer cont
aining the imino form of cytosine is more stabilized by water cluster than
that containing its amino forms. The possible biological significance stems
from the fact that the cytosine in the dimer directs the incorporation of
adenine in the complementary strand during replicative bypass, Data obtaine
d point to the cytosine tautomerism as a possible mechanism for the origin
of UV-induced mutation.