The synthesis of an oligonucleotide (ODN) modified with pyrene (pyr) on the 5'-phosphate is described. The ODN and pyrene are joined through a linker composed of four methylene groups. Modification of the oligonucleotide was effected via condensation of the 2-cyanoethyl N,N-diisopropylphosphoramidite of 4-(1-pyrenyl)butanol (pyr-m4OPAm, 2) with the 5'-OH of an ODN. This derivative is suitable for incorporation into automated solid-phase DNA synthesis and was attached to the 5' terminus of the DNA chain through a phosphodiester linkage. The properties of the 5'-(pyr-m4)d(T)15 (3) and the duplex it formed with d(A)15 were investigated by fluorescence and absorbance spectroscopy. The pyrene fluorescence in the modified duplex was quenched 96.3% relative to an identical concentration of free 4-(1-pyrenyl)butanol. The ultraviolet spectrum of the 5'-(pyr-m4)-d(T)15 and 5'-(pyr-m4)-d(T)15-d-(A)15 modified duplex, in the 320-360-nm region, was red-shifted 6 nm relative to the free 4-(1-pyrenyl)-butanol. The Tm values of the unmodified and modified duplexes at 0.1 M NaCl were 34.9 and 41.9 degrees C, respectively. The pyrene-induced stabilization corresponds to a free energy change (delta delta G degrees) of -2.6 kcal/mol.

The effect of DNA loadings on the thermal stability of DNA duplex immobilized on gold nanoparticles has been investigated. The modestly loaded duplexes on the gold nanoparticles showed enhanced thermal stability, as compared to that of the free duplex (without gold nanoparticles). However, the highly loaded duplex showed stability similar to that of free duplex. The stability could be controlled over a wide temperature range simply by varying the salt concentration (over 50 degrees C). Additionally, the gold nanoparticles with modestly loaded oligonucleotides could be used as nanoprobes for effective and fast strand exchange reactions, based on the increased thermal stability of the immobilized duplex. These results indicate that the interaction between the duplex and the nanoparticle surface plays an important role in determining the stability of the duplex.

100 picoliter droplet handling with 256 (2 8 ) microvalves is demonstrated. The 256 microvalves are positioned on the 256 cross points of 16 vertical fluidic channels and 16 horizontal fluidic channels. 256 microvalves are individually controlled by multiplexed pneumatic circuit having only 18 (2*8+2) pneumatic control lines. The 100 picoliter order droplet of sample is handled in inert liquid to avoid evaporation. The droplets about 100 pl are successfully transferred to any directions by 256 microvalves.

The dependence of donor-acceptor pair (DAP) emission properties on impurity concentrations of N and B in 6H-SiC epilayers was investigated. Doped samples were grown by closed sublimation technique, and impurity concentrations were confirmed by secondary ion mass spectrometry (SIMS). Photoluminescence (PL) measurement results indicate that p-type 6H-SiC with NA>ND had extremely low DAP emission efficiency, whereas n-type 6H-SiC with NA<ND showed intense DAP emission. Moreover, n-type 6H-SiC with high N and B concentrations exceeding 1018cm-3 is preferable for high DAP emission efficiency.