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.

Synthesis and properties of novel PRODAN-labeled uridine.

We have developed a novel base-discriminating fluorescent (BDF) nucleoside, (PDN)U, which contains a PRODAN chromophore connected at the C-5 position of uracil. The Stokes shift (Deltanu) of (PDN)U was highly dependent on the local dielectric property around the fluorophore. On the excitation at 450 nm, the fluorescence spectrum of the duplex containing a (PDN)U/A base pair showed a strong emission at 520 nm. In contrast, the fluorescence intensities of duplexes containing "mismatched" (PDN)U/N base pairs (N = C, G, or T) were considerably lower. Furthermore, the drastic change of fluorescence intensity by the nature of the complementary base is useful for SNP typing.

Development of novel PRODAN-labeled nucleosides as base-discriminating fluorescent probes.

We have developed a PRODAN-labeled uridine ((PDN)U), which contains a polarity-sensitive chromophore at the C-5 position of uracil. This paper describes the synthesis and fluorescent properties of oligodeoxy-nucleotides (ODNs) containing PRODAN-labeled nucleosides ((PDN)C, (PDN)A, and (PDN)G). PRODAN chromophore was attached to cytosine at the C-5 position and to purine bases at the C-8 position to extend into the major groove. When BDF probes containing a PRODAN-labeled nucleoside hybridize with a "full-matched" ODN, the fluorescence spectrum showed a strong emission around 520 nm on 450 nm excitation. In contrast, when PRODAN-labeled nucleoside analogs form a "mismatched" base pair, the fluorescence was weaker.

Monitoring DNA structures by dual fluorescence of pyrene derivatives.

We have developed a nucleotide modified by a pyrene derivative with dual fluorescence. The dual fluorescence of the fluorophore, which was incorporated into DNA, was effectively controlled at ambient temperature according to DNA structural status. Our nucleoside with dual fluorescence is effective as a conceptually new probe for monitoring DNA hybridization by the color change without multilabeling with fluorescent dyes.

Synthesis of an artificial hole-transporting nucleoside triphosphate, dMDATP, and its enzymatic incorporation into DNA.

We report on the enzymatic synthesis of DNA wires by successive incorporation of artificial nucleotides. We synthesized an efficient hole-transporting nucleoside triphosphate, d(MD)ATP, and have examined the screening of polymerases and reverse transcriptases for enzymatic incorporation of d(MD)ATP into DNA. We found that KOD Dash is an effective enzyme for the enzymatic synthesis of (MD)A-containing DNA. Furthermore, the efficiency of enzymatic incorporation was remarkably improved by the addition of manganese chloride. By applying the PCR method to the synthesis of DNA containing a run of (MD)A, the (MD)A run was amplified up to 6 x 10(6) times. (MD)A runs prepared by the enzymatic method exhibited a high hole-transporting ability.

Synthesis and fluorescence properties of oligonucleotides containing pyrene-dimethylaniline chromophore.

The photophysical properties of DNA oligomers containing novel uracil derivatives tethering a solvatochromic pyrene-dimethylaniline (Py-DMA) chromophore were investigated. In the steady-state fluorescence measurements of the modified DNA oligomer, dual fluorescence, originating from a locally excited (LE) and a twisted intramolecular charge transfer (TICT) state, was observed.

Enzymatic ligation and extension of DNA wire.

The ODNs containing (MD)A, which effectively mediate hole transport, were enzymatically ligated, and photo-induced hole transport reaction proceeded efficiently through a ligated long duplex. The ligated duplex showed high hole transport efficiency.