Highly emissive deoxyguanosine analogue capable of direct visualization of B–Z transition

Abstract

A 2-aminothieno[3,4-d]pyrimidine G-mimic deoxyribonucleoside, (th)dG, was synthesized and incorporated readily into oligonucleotides as a versatile fluorescent guanine analogue. We demonstrate that (th)dG enables the visual detection of Z-DNA successfully based on different π-stacking of B- and Z-DNA.

Tautomers of a Fluorescent G Surrogate and Their Distinct Photophysics Provide Additional Information Channels

“…Thus, by judiciously selecting the excitation and emission wavelengths, each tautomer can be individually excited and observed. The fluorescence quantum yield (QY) is found to be constant (0.49±0.03) over a large range of excitation wavelengths (λ=290–375 nm) and close to earlier reported values, [5a,c] thus indicating that the two forms possess similar QY values. The individual absorption spectrum of the red-shifted form (Figure 2c) is very similar to the spectra of th G and d th G in 1,4-dioxane.…”

“…[5a,b] Excitation at both λ=360 and 380 nm gives a similar emission spectrum (Figure 2a, orange) centered at λ=468 nm. When the excitation energy is progressively increased, a blue-shifted emission with a maximum at λ=400 nm appears and becomes dominant for excitation below λ=300 nm (Figure 2a, magenta and blue).…”

“…A tautomerizable nucleoside analogue, where the tautomers would have distinct absorption and emission spectra, could be instrumental for investigating the micro-environment of a nucleobase with greater insight compared to tautomerically stable probes. Herein we analyze the photophysics of thienoguanosine, th G, a highly useful G surrogate, [5] and identify two environmentally sensitive ground-state tautomeric forms (Figure 1) which display distinct absorption and emission spectra. The equilibrium between the two tautomers is mainly governed by the hydrogen-bond donor properties of the solvent.…”

“…The individual absorption spectrum of the red-shifted form (Figure 2c) is very similar to the spectra of th G and d th G in 1,4-dioxane. [5a,b] By using the molar extinction coefficient of th G in 1,4-dioxane (ε 333 =4530 m −1 cm −1 ), [5a] it is possible to calculate the concentration of the red-shifted tautomer in buffer and deduce the proportion (44%) and the molar extinction coefficient (ε 313 ≈4600 m −1 cm −1 ) of the blue-shifted tautomer. Importantly, the red-shifted tautomer, excited at λ=350–380 nm, is highly photostable (see Figure S2).…”

Synthesis, Photophysical Properties, and Enzymatic Incorporation of an Emissive Thymidine Analogue

“…30 This can be applied in solid-phase oligonucleotide synthesis; moreover, a guanosine triphosphate analogue, th dGTP, was also synthesized and enzymatically incorporated into DNA through primer extension and PCR amplification. 31 Very recently, we have focused on nucleotide modifications to enhance the utility of th dG and synthesized a highly emissive 2¤-O-methylated guanosine analogue, 2¤-OMeth G. 32 The bright blue light of 2¤-OMeth G combined with the distinctive BZ transition of DNA has the potential for application as a visible nanothermometer.…”