Jg. Muller et al., DNA AND RNA MODIFICATION PROMOTED BY [CO(H2O)(6)]CL-2 AND KHSO5 - GUANINE SELECTIVITY, TEMPERATURE-DEPENDENCE, AND MECHANISM, Journal of the American Chemical Society, 118(10), 1996, pp. 2320-2325
Reaction of a single-stranded oligodeoxynucleotide or a 17-base hairpi
n-forming oligodeoxynucleotide with CoCl2 and KHSO5 produced guanine-s
pecific cleavage after piperidine treatment. The observed reactivity i
s shown to be nearly twice that obtained for NiCR icyclo[11.3.1]heptad
eca-1(17),2,11,13,15-pentaene) under equivalent conditions, although N
iCR displays a slightly higher degree of selectivity for unpaired guan
ine residues. Cobalt-induced DNA modification was catalytic with respe
ct to the,metal complex and was observed at temperatures up to 80 degr
ees C, conditions under which NiCR was ineffective. Mechanistic studie
s of the cobalt-mediated reaction suggest that SO4.- is responsible fo
r guanine oxidation. Reaction with tRNA(Phe) induced aniline . HOAc-la
bile (pH 4.5) lesions also at accessible guanine sites. The high react
ivities of G20 acid G34 are consistent with attack of SO4.- on the rr
face of the guanine heterocycle as opposed to recognition of G N7 as p
roposed for NiCR. CoCl2 should become an extremely attractive probe of
nucleic acid structure since it induces base-specific and conformatio
n-specific cleavage of DNA under a much wider variety of experimental
conditions than NiCR, acts with a different mode of guanine selectivit
y than do nickel complexes, and is commercially available.