Nuclease tolerant FRET probe based on DNA-quantum dot conjugation.

We have developed a fluorescence resonance energy transfer (FRET) probe based on the conjugation of a quantum dot (QD) with dye (YOYO-3) intercalated DNA. The FRET-inducing electrostatic coupling of DNA and the QD made structural changes to the QD-DNA conjugates, which significantly prevented an enzymatic reaction between the DNA and a conventional restriction endonuclease (EcoRI).     

Quantum dot-insect neuropeptide conjugates for fluorescence imaging, transfection, and nucleus targeting of living cells

We identified an insect neuropeptide, namely, allatostatin 1 from Drosophila melanogaster, that transfects living NIH 3T3 and A431 human epidermoid carcinoma cells and transports quantum dots (QDs) inside the cytoplasm and even the nucleus of the cells. QD-conjugated biomolecules are valuable resources for visualizing the structures and functions of biological systems both in vivo and in vitro. Here, we selected allatostatin 1, Ala-Pro-Ser-Gly-Ala-Gln-Arg-Leu-Tyr-Gly-Phe-Gly-Leu-NH2, conjugated to streptavidin-coated CdSe-ZnS QDs. This was followed by investigating the transfection of live mammalian cells with QD-allatostatin conjugates, the transport of QDs by allatostatin inside the nucleus, and the proliferation of cells in the presence of allatostatin. Also, on the basis of dose-dependent proliferation of cells in the presence of allatostatin we identified that allatostatin is not cytotoxic when applied at nanomolar levels. Considering the sequence similarity between the receptors of allatostatin in D. melanogaster and somatostatin/galanin in mammalian cells, we expected interactions and localization of allatostatin to somatostatin/galanin receptors on the membranes of 3T3 and A431 cells. However, with QD conjugation we identified that the peptide was delivered inside the cells and localized mainly to the cytoplasm, microtubules, and nucleus. These results indicate that allatostatin is a promising candidate for high-efficiency cell transfection and nucleus-specific cell labeling. Also, the transport property of allatostatin is promising with respect to label/drug/gene delivery and high contrast imaging of live cells and cell organelles. Another promising application of allatostatin is that the transport of QDs inside the nucleus would lift the limit of general photodynamic therapy to nucleus-specific photodynamic therapy, which is expected to be more efficient than photosensitization at the cell membrane or in the cytoplasm as a result of the short lifetime of singlet oxygen.     

An organic electroluminescent device with a molecularly doped polymer hole transport layer

Electroluminescent(EL) devices have been fabricated using four different polymers with different glass transition temperatures (T_g) dispersed with N,N′-bis-(3-methylphenyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine (TPD) as a hole transport layer and tris(8-hydroxyquinoline) aluminum (Alq₃) as an emitting layer. It was found that the higher the T_g of the polymer, the longer the lifetime of the device. From observations of TPD-doped polymer films with optical microscope and atomic force microscope, dispersing TPD in the polymers was found to suppress the crystallization that causes the roughness of the film surface. It was also observed that the higher the T_g of the host polymers, the more difficult TPD crystallization was. The property of the EL device with polyethersulfone (PES) dispersed with TPD was also investigated. The lifetime of EL device with the TPD doped PES film was improved more than five times at a current density below 10 mA/cm² compared with the device with a conventional TPD hole transport layer. © 1997 John Wiley & Sons, Ltd.     

Synthesis and thermal properties of cellulose-based polycaprolactones

Cellulose-based polycaprolactone (CAPCL) sheets were prepared from cellulose acetate (CA) and ϵ-caprolactone (CL). Thermal properties of the obtained CAPCL's were studied by differential scanning calorimetry (DSC), thermogravimetry (TG) and TG-Fourier transform infrared spectrometry (TG-FTIR). The glass transition temperatures (T_g 's) of CAPCL decreased with increasing CL/OH ratio, until CL/OH ratio reached 15 and then increased above that ratio. Melting of CAPCL was observed when CL/OH ratio was over 10. The thermal degradation temperatures (T_d 's) of CAPCL increased from ca. 350 °C to 390 °C with increasing CL/OH ratio. The results obtained by TG-FTIR analysis of CAPCL showed that gases with OH, CH, C=O, C-O-C groups evolved by thermal degradation.     

Phase behavior and fluid-solid surface tension of argon in slit pores and carbon nanotubes

Phase behaviors of argon in several types of cylindrical and slit pores are examined by grand-canonical Monte Carlo simulations. Condensation processes in single- and multi-walled carbon nanotubes along with those in hard-wall tubes are compared. Effects of the pore size on pressure-tensor components, the fluid-wall surface tension, and the adsorption are also compared for the different fluid-pore interactions. The chemical potential at which the fluid begins to condense in the single-walled nanotube is greater than that in the multi-walled nanotube by an amount nearly equal to the difference in the potential-well depth of the fluid-pore interaction, and the adsorption isotherms overlap each other almost completely for narrow pores and partially for wider pores. Similar analyses are performed for slit pores of two different hydrocarbon models.     

Electrochemical reactors for NO decomposition. Basic aspects and a future

The electrochemical reduction of nitric oxide in the presence of the excess oxygen was reviewed. It was shown that the selectivity and activity of the cathodes is strongly dependent on the composition and on the microstructure of the cathode material. A concept of electrochemical reactor with multilayer electro-catalytic electrode was proposed and successfully designed in Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), Nagoya, Japan. The typical values of current efficiency in such electrochemical reactors are of the order of 10–20% at gas composition: 1,000 ppm NO and 2% O₂ balanced in He and at gas flow rate 50 ml/min. The value of current efficiency depends on the functional multi-layer electrode composition, structure, and operating temperature. Such electrochemical reactors show the value of NO/O₂ selectivity (ν _sel) higher than 5 (ν _sel > 5) at intermediate temperature and up to ν _sel = 25 at low temperature operation. It was shown that multilayer electro-catalytic electrode should consist at list from three main functional layers: cathode, electro-catalytic electrode, covering layer, in order to operate as an electrode with high selectivity.     

The Weight-Bearing Rate on the Paretic Limb of Cerebrovascular Hemiplegic Patients Necessary for an Independent Obstacle Negotiation Gait

Purpose: The obstacle negotiation gait (ONG) is a fundamental activity of daily living. In cerebrovascular hemiplegic patients (stroke patients), the weight-bearing rate (WBR) on the paretic limb necessary for an independent ONG was studied. Methods: One hundred and seventeen stroke patients were involved. The patients'' average age at the time of the study was 67 years, and the average time from stroke onset was 102 days. There were 68 men and 49 women. Seventy patients were right hemiplegics, and 47 were left hemiplegics. The correlations between ONG and age, sex, body mass index (BMI), time from stroke onset, muscle strength of both the paretic and non-paretic limbs, Brunnstrom stage of the lower limbs, deep sensation, and the WBR on both the paretic and non-paretic limbs were studied. Patients who could perform ONG independently and safely were categorized as the independent group (IG), and those who needed observation or any assistance were categorized as the dependent group (DG). Results: The BMI, muscle strength of both the paretic and non-paretic limbs, Brunnstrom stage of the lower limbs, deep sensation and the WBR for both the paretic and non-paretic limbs were significantly different between the IG and DG groups. In particular, the WBR on the paretic limb was found to correlate significantly with the ONG, and a WBR value of 80.5% on the paretic limb gave a clear cut-off value. Conclusion: Although multiple factors influenced the ONG of stroke patients, the WBR on the paretic limb was the most influential.