Fluorescence Properties of 5‐(5,6‐Dimethoxybenzothiazol‐2‐yl)‐2′‐deoxyuridine (dbtU) and Oligodeoxyribonucleotides Containing dbtU

Abstract

AbstractWe describe the synthesis and photophysical properties of 11 substituted 5‐(benzothiazol‐2‐yl)‐2′‐deoxyuridine derivatives and oligodeoxyribonucleotides (ODNs) containing 5‐(5,6‐dimethoxybenzothiazol‐2‐yl)‐2′‐deoxyuridine (dbtU), which was the strongest fluorescent derivative among those prepared. The fluorescence properties of dbtU itself and ODNs containing dbtU show the same tendency of being weaker in both neutral and acidic solution and stronger in basic solution. The ODNs (15mer) containing 16 combinations of 5′‐XbtU‐3′ and 5′‐btUY‐3′, where X, Y = A, T, G, or C, were synthesized, and their fluorescence intensity and quantum yield in basic solution were compared. On average, only the ODN with the 5′‐GbtU‐3′ sequence shows a 7.9‐fold lower fluorescence intensity than the other sequences. Ab initio calculations of 5′‐GbtU‐3′ and 5′‐btUG‐3′ as models under basic conditions suggest that the lower fluorescence of the ODN containing the 5′‐GbtU‐3′ sequence is caused by a wider overlap between stacked guanine (Gua) and btUra than that of the 5′‐btUG‐3′ sequence and that the HOMO is delocalized not only on btUra but also on Gua.