M. Novak et Sa. Kennedy, INHIBITORY EFFECT OF DNA-STRUCTURE ON THE EFFICIENCY OF REACTION OF GUANOSINE MOIETIES WITH A NITRENIUM ION, Journal of physical organic chemistry, 11(1), 1998, pp. 71-76
The N-acetyl-N-(2-fluorenyl)nitrenium ion (2a) reacts very efficiently
with monomeric 2'-deoxyguanosine (d-G) to form a C-8 adduct, N-(2'-de
oxyguanosin-8-yl)-2-acetylaminofluorene (6), in an aqueous environment
, with a selectivity ratio, k(d-G)/k(s), of 13.1 x 10(3) M-1 at 0 degr
ees C and 4.8 x 10(3) M-1 at 30 degrees C. The reactivity of the self-
complementary oligomer d-ATGCAT with 2a can be separated into componen
ts due to the single-stranded (SS) and double-stranded (DS) forms. Wit
hin the error limits of the measurements k(SS)/k(d-G) approximate to 0
.27 and k(DS)/k(d-G) approximate to 0. Another measure of the reactivi
ty of d-G moieties in the DNA double helix can be obtained from measur
ements with the circular super-coiled plasmid pUC19. This plasmid prov
ides an upper limit for k(pUC19)/k(d-G) of 0.02, where k(pUC19) is the
average trapping rate constant per d-G moiety in pUC19. The strong in
hibition of the trapping reaction caused by the tertiary structure of
the DNA double helix may be responsible for the change in product dist
ribution of 2a-d-G adducts found from reaction with d-G, and denatured
DNA (exclusive C-8 adduct, 6) and native DNA [5-20% N-2 3-(2'-deoxygu
anosin-N-2-yl)-2-acetylaminofluorene, 7]. (C) 1998 John Wiley & Sons,
Ltd.