PRODAN-conjugated DNA: synthesis and photochemical properties.

A solvatochromic fluorophore, PRODAN, has been used as a microenvironment-sensitive reporter. Based on the chemistry of PRODAN, we designed and synthesized four novel fluorescent nucleosides, PDNX (X = U, C, A, and G), to which a PRODAN fluorophore was attached at pyrimidine C5 or purine C8. The fluorescent nucleosides sensitively varied the Stokes shift values depending on the orientational polarizability of the solvent. The PDNX incorporated into DNA also changed the Stokes shift values depending on the DNA structure. In particular, the excitation spectrum of the PDNX-containing duplex shifted to a longer wavelength and gave a smaller Stokes shift value when the base opposite PDNX could form a Watson-Crick base pair with PDNX. A lower energy excitation of PDNX-containing DNA resulted in a strong fluorescence emission selective to the Watson-Crick pairing base. This unique photochemical character was applicable to the efficient typing of single-nucleotide polymorphisms of genes.