S1-state internal conversion of isolated azulene derivatives.

The S0-S1 hole-burning spectra of azulene and its derivatives, 1-methyl, 2-methyl, 4-methyl, 1-cyano, and 2-cyanoazulenes, were measured under the isolated condition in order to gain an insight into the internal-conversion mechanism. The width of every 0-0 band was dependent on its transition energy and independent of the density of the S0-state vibrational levels isoenergetic to its zero level of the S1 state. On the contrary, the vibronic-band broadening of each molecule progressed in proportion to the vibrational excess energy of the S1 state. In the low-energy region, widths gradually increased, which is attributed to the normal internal conversion. A drastic increase was observed in the medium-energy region in azulene and three methyl derivatives but not in the two cyano ones. This is considered to be the onset of the relaxation process due to the conical intersection suggested by Bearpark et al. [J. Am. Chem. Soc. 1996, 118, 169]. Anomalous width behavior was found for two vibronic bands whose widths were still narrow even above the onset. One was 0 + 2659 cm(-1) band of azulene, that had been already reported by Ruth et al. [Phys. Chem. Chem. Phys. 1999, 1, 5121], and we could reproduce it by the hole-burning method. Another was 0 + 2878 cm(-1) band of 2-methylazulene. This is the vibronic selectivity in competition between the relaxation process and the normal internal conversion. The amplitude vectors of these modes were similar, including the in-plane bending of the CH bond and the stretching of the transannular bond.

Design of a novel G-quenched molecular beacon: a simple and efficient strategy for DNA sequence analysis.

G-quenched MBs are devised from readily available starting materials and used for sequence specific DNA detection with high efficiency.

Design of dual-labeled oligonucleotide probes for SNPs genotyping.

Our effort in designing base-discriminating fluorescence nucleosides (BDF), leads us to develop dual-labeled oligonucleotide probe in which the BDF nucleoside, (Py)U/(2-Ant)U act as the donor separated by a defined base pair distance from the acceptor, fluorescein, attached to 5'-end of the probe. Thus, a longer wavelength emission from acceptor might allow the probe to be used for SNP typing in chip based detection technology or in cell.

Synthesis of C8-alkylamino substituted 2'-deoxyguanosine.

Synthesis of C8-alkynyl- and alkylamino substituted 2'-deoxyguanosine is described. Protected alkynylamines are coupled with 8-bromo-2'-deoxyguanosine by a Pd(0)-mediate Sonogashira coupling protocol. Hydrogenation of alkynyl derivatives over 10% Pd/C under atmospheric pressure gave 8-alkylamino guanosine derivatives in nearly quantitative yields.

Dual-labeled oligonucleotide probe for sensing adenosine via FRET: a novel alternative to SNPs genotyping.

A novel FRET based strategy for DNA sequence analysis utilising base-discriminating fluorescence (BDF) nucleoside, (Py)U/(2-Ant)U, as donor in the dual-labelled oligonucleotide probe is reported; a selective/specific emission from acceptor, was observed upon excitation at the donor, only when the opposite base of the "smart" fluorescently labeled BDF nucleoside, (Py)U/(2-Ant)U, is adenine on the complementary target sequence.

Synthesis of perylene-labeled base-discriminating fluorescent (BDF) nucleoside and its fluorescence properties.

We have synthesized perylene labeled BDF probe and its photophysical properties were explored. Perylene labeled oligonucleotide probe is capable of detecting cytosine from its target mismatch sequence by enhancement of fluorescence intensity.

Luminescence properties of dual fluorescent pyrene derivatives used as DNA probe molecule.

We examined the dual fluorescence mechanism of 8-[4-(dimethylamino)phenyl]-N-2-propynyl-1-pyrenecarbox-amide (PyADMA) in polar solvent. The emission band appeared on the short wavelength side does not depend on the solvent polarity. On the other hand, the red shifted emission band depends on solvent polarity. On the face of it, the phenomenon is similar to intramolecular charge transfer (ICT) dynamics of 4-dimethylamino benzonitrile (DMABN). However, direct absorption band from ground state to ICT state is observed on the fluorescence excitation spectrum at room temperature. It is suggest that PyADMA would emit from both S(1) and S(2) state against the Kasha rule. On the other hand, we also examined the interaction between PyADMA and nucleoside which composing PyDMA-U in water solution. We found out that dynamics of excited states of PyADMA monomer is different from them of PyDMA-U.

Intelligent fluorescent nucleoside in sensing cytosine base: importance of hydrophobic nature of perylene fluorophore.

Fluorescence response upon hybridization of perylene labeled oligonucleotide probes depends on the microenvironment experienced by the perylene fluorophore. In mismatched duplex ((Per)U-C), enhanced fluorescence was observed while in matched duplex ((Per)U-A) fluorescence intensity decreased considerably. This observation will be a promising research effort in giving rise to a new powerful tool in detection of SNP.