C8?Heteroaryl-2′-deoxyguanosine Adducts as Conformational Fluorescent Probes in the NarI Recognition Sequence

摘要

The optical, redox, and electronic properties ofnC8-heteroaryl-2′-deoxyguanosine (dG) adducts with C8-substituentsnconsisting of furyl (FurdG), pyrrolyl (PyrdG), thienyln(ThdG), benzofuryl (BfurdG), indolyl (InddG), and benzothienyln(BthdG) are described. These adducts behave as fluorescentnnucleobase probes with emission maxima from 379 to 419 nmnand fluorescence quantum yields (Φf l) in the 0.1−0.8 range innwater at neutral pH. The probes exhibit quenched fluorescencenwith increased solvent viscosity and decreased solvent polarity.nThe FurdG, BfurdG, InddG, and BthdG derivatives werenincorporated into the G3 position of the 12-mer oligonucleotiden5′-CTCG1G2CG3CCATC-3′ that contains the recognitionnsequence of the NarI Type II restriction endonuclease. Thisnsequence is widely used to study the biological activity (mutagenicity) of C8-arylamine−dG adducts with adduct conformationn(anti vs syn) playing a critical role in the biological outcome. The modified NarI(X = FurG, IndG, BfurG, or BthG) oligonucleotidesnwere hybridized to the complementary strand containing either C (NarI′(C)) or G (NarI′(G)) opposite the probe. The duplexnstructures were characterized by UV melting temperature analysis, fluorescence spectroscopy, collisional fluorescence quenchingnstudies, and circular dichroism (CD). The emission of the probes showed sensitivity to the opposing base in the duplex, andnsuggested the utility of fluorescence spectroscopy to monitor probe conformation.