Nucleic acid base analogs with quenching and fluorescent activities and applications thereof

A method of detecting formation of a base pair of artificial bases, the method comprising:

• observing a decrease in fluorescence of an artificial fluorescent base, wherein
• the decrease in fluorescence of an artificial fluorescent base is caused by formation of a base pair of an artificial fluorescent base and a quenching base, wherein
• the artificial fluorescent base is selected from the group consisting of:
• (i) a 7-(2,2′-bithien-5-yl)imidazo[4,5-b]pyridin-3-yl group (Dss);
• (ii) a 7-(2,2′,5′,2″-terthien-5-yl)imidazo[4,5-b]pyridin-3-yl group (Dsss);
• (iii) a 2-amino-6-(2,2′-bithien-5-yl)purin-9-yl group (ss);
• (iv) a 2-amino-6-(2,2′,5′,2″-terthien-5-yl)purin-9-yl group (sss);
• (v) a 4-(2,2′-bithien-5-yl)-pyrrolo[2,3-b]pyridin-1-yl group (Dsas);
• (vi) a 4-[2-(2-thiazolyl)thien-5-yl]pyrrolo[2,3-b]pyridin-1-yl group (Dsav);
• and
• (vii) a 4-[5-(2-thienyl)thiazol-2-yl]pyrrolo[2,3-b]pyridin-1-yl group (Dvas);
• and
• the quenching base having a 2-nitropyrrole structure is represented by Formula III or IV:
• wherein R3 is selected from —H, iodine, —CH3, and:
• wherein R4 is selected from —CH3, —CH2—NH2, and:
• wherein n is an integer of 0 to 12, and
• wherein the nitrogen atom at the 2-position of the 2-nitropyrrole structure is attached to a ribose or deoxyribose to form a nucleoside or nucleotide.