1 research outputs found
7-Deazapurine and 8-Aza-7-deazapurine Nucleoside and Oligonucleotide Pyrene “Click” Conjugates: Synthesis, Nucleobase Controlled Fluorescence Quenching, and Duplex Stability
7-Deazapurine and 8-aza-7-deazapurine nucleosides related
to dA
and dG bearing 7-octadiynyl or 7-tripropargylamine side chains as
well as corresponding oligonucleotides were synthesized. “Click”
conjugation with 1-azidomethyl pyrene (<b>10</b>) resulted in
fluorescent derivatives. Octadiynyl conjugates show only monomer fluorescence,
while the proximal alignment of pyrene residues in the tripropargylamine
derivatives causes excimer emission. 8-Aza-7-deazapurine pyrene “click”
conjugates exhibit fluorescence emission much higher than that of
7-deazapurine derivatives. They are quenched by intramolecular charge
transfer between the nucleobase and the dye. Oligonucleotide single
strands decorated with two “double clicked” pyrenes
show weak or no excimer fluorescence. However, when duplexes carry
proximal pyrenes in complementary strands, strong excimer fluorescence
is observed. A single replacement of a canonical nucleoside by a pyrene
conjugate stabilizes the duplex substantially, most likely by stacking
interactions: 6–12 °C for duplexes with a modified “adenine”
base and 2–6 °C for a modified “guanine”
base. The favorable photophysical properties of 8-aza-7-deazapurine
pyrene conjugates improve the utility of pyrene fluorescence reporters
in oligonucleotide sensing as these nucleoside conjugates are not
affected by nucleobase induced quenching