We illustrate a general polymeric design of fluorescent logic gates, for example, AND, using temperature and pH as inputs.

Poly(N-isopropylacrylamide) in aqueous solution undergoes a phase transition at approximately 32 degrees C. The fluorescence properties of benzofurazans are affected by solvent polarity. We combine these two characteristics for the first time to develop sensitive fluorescent molecular thermometers. Five fluorescent monomers having a benzofurazan skeleton were synthesized, and the copolymers of N-isopropylacrylamide (NIPAM) and a small quantity of the fluorescent monomer were obtained to investigate their fluorescence properties. With increase in temperature, the copolymers in water showed the temperature-induced phase transition at approximately 32 degrees C and the fluorescence intensities of the copolymers concurrently increased. Especially, for the copolymer of 4-N-(2-acryloyloxyethyl)-N-methylamino-7-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole and NIPAM, the fluorescence intensity at 37 degrees C was 13.3-fold that seen at 29 degrees C. The sensitive range of temperature of these fluorescent molecular thermometers is changed by the replacement of the NIPAM units by N-isopropylmethacrylamide or N-n-propylacrylamide units in the copolymers. The basis of these fluorescent molecular thermometers is the decrease in the microenvironmental polarities near the main chains of the copolymers with increasing temperature, as confirmed from the maximum emission wavelengths of the benzofurazan units in the copolymers. The responses from the copolymers to the change in temperature are reversible and exactly repeatable during at least 10 cycles of heating and cooling.

The inwardly rectifying K ؉ channel subunit Kir5.1 is expressed abundantly in the brain, but its precise distribution and function are still largely unknown. Because Kir5.1 is co-expressed with Kir4

Phase transitions in aqueous solutions of poly(N-isopropylacrylamide) (PNIPAM) with a molecular weight (M h w) of 63 000 were achieved by irradiating the solutions (0.2-3.6 wt %) with an IR laser beam (1064 nm) through an optical microscope. First, a microparticle with the size of the focused laser beam was formed (=1.5 µm). This microparticle continuously grew and after prolonged irradiation (up to 10 min), a microparticle with a maximum size of 25 µm was obtained. Upon further irradiation, the microparticle became unstable and finally disappeared. The importance of the optical alignment of the microscope/laser system is discussed. Particle formation was also found in D 2O solutions of PNIPAM. These experimental results indicate that, besides a photothermal effect (heating up of the solution due to absorption of water at 1064 nm), there is influence of the "radiation force" upon particle formation and conformation properties of the polymer. The observations mentioned above are discussed in connection with the theory of the single beam gradient force optical trap for dielectric particles.

No abstract

We showed that CD9, a member of tetraspanin superfamily proteins, is expressed in a specific membrane microdomain, called "lipid raft," and is crucial for cell fusion during osteoclastogenesis after activation of the RANK/RANKL system. Introduction: Osteoclasts are bone-resorbing multinuclear polykaryons that are essential for bone remodeling and are formed through cell fusion of mononuclear macrophage/monocyte lineage precursors. Although osteoclastogenesis has been shown to be critically regulated by the RANK/RANKL system, the mechanism how precursor cells fuse with each other remains unclear. We examined the function of CD9, a member of tetraspanin superfamily, which has previously been shown to form macromolecular membrane microdomains and to regulate cell-cell fusion in various cell types. Materials and Methods: We used RAW264.7, a macrophage/monocyte lineage cell line, which can differentiate into osteoclast-like polykaryons on the application of RANKL. Expression and distribution of CD9 was assessed by Western blotting, fluorescence-assorted cell sorting (FACS) and immunohistochemistry with light and electron microscopy. A specific neutralizing antibody and RNA interference were used to inhibit the function of CD9, and green fluorescent protein (GFP)-CD9 was exogenously expressed to enhance the effect of CD9. The distribution of CD9 in lipid microdomain was examined by biochemical (sucrose density gradient) isolation and imaging technique. Results: CD9 is expressed on cell surfaces of RAW264.7, which is enhanced by RANKL. Targeted inhibition of CD9 decreases the number of osteoclast-like cells. On the other hand, overexpression of CD9 promotes spontaneous cell fusion even in the absence of RANKL. CD9 is localized in detergent-insoluble "lipid raft" microdomain in RANKL stimulation, and disruption of lipid rafts markedly reduces the formation of osteoclast-like polykaryons. Immunohistochemical studies of bone tissues revealed the expression of CD9 in osteoclasts in vivo. Conclusions: These data suggest that function of tetraspanin CD9 and its expression in lipid rafts are crucial for cell fusion during osteoclastogenesis.

Intramolecular photoinduced electron transfer in 9-(p-N,N-dimethylanilino)phenanthrene (9DPhen) has been studied in solution. The solvent dependence of the fluorescence spectra of 9DPhen indicates that the emission occurs from a highly polar excited state. The quantum yield of fluorescence (Φ f ) of 9DPhen is quite high and increases with increasing solvent polarity. The radiative rate constant (k f ), however, shows a maximum for solvents of intermediate polarity, e.g., in butyl acetate a value of 2.3 × 10 8 s -1 is attained. These results are difficult to explain within the "TICT" (twisted intramolecular charge transfer) model, which predicts a strongly forbidden fluorescence caused by a minimum overlap of the orbitals involved in the transition. The above-mentioned trend as a function of the solvent polarity is observed in particular donor-acceptor substituted arenes where the L b state of the corresponding arenes is lower in energy than the L a state. The quantum chemical calculations actually could explain this behavior on the basis of an ICT state which interacts with the lower lying 1 L a and 1 L b states of the acceptor. The quantum mechanical mixing of states can occur by two pathways, namely orbital mixing and mixing of configurations, and is modified by geometrical changes and by solvent polarity. The single exponential fluorescence decay, obtained with time-correlated single-photon-timing, suggests emission from an excited charge-transfer state, resulting from a solvent-induced rapid relaxation of the initial delocalized excited state of 9DPhen, obtained immediately after picosecond pulsed excitation. Picosecond transient absorption spectra in acetonitrile show a rapid decay within a few picoseconds from a less polar but delocalized excited state toward a more polar ICT state. Even the triplet state of 9DPhen in isopentane at 77 K shows a significant polar character. As a reference compound, 9-phenylphenanthrene (9PhPhen) was also examined by means of stationary and time-resolved fluorescence measurements as well as transient absorption experiments.

Fluorescent molecular thermometers based on polymers showing a temperature-induced phase transition and labeled with polarity-sensitive fluorescent benzofurazans are the most sensitive known. Here we show a simple and effective method for modulating the sensitive temperature ranges of fluorescent molecular thermometers based on such temperature-responsive polymers. 4-N-(2-acryloyloxyethyl)-N-methylamino-7-N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole was adopted as a polarity-sensitive fluorescent benzofurazan, and nine copolymers of two kinds of acrylamide derivative (N-n-propylacrylamide, N-isopropylacrylamide, and/or N-isopropylmethacrylamide) with a small amount of DBD-AE were obtained. The fluorescence intensities of these copolymers in aqueous solution sharply increased with increasing temperature over a small range (6-7 degrees C). In contrast, these fluorescent molecular thermometers differed from one another in the sensitive temperature range (between 20 and 49 degrees C). Moreover, the sensitive temperature ranges were well related to the acrylamide ratios in feed. In addition, the responses from these fluorescent molecular thermometers to the change in temperature were reversible and exactly repeatable during 10 cycles of heating and cooling (relative standard deviation of the fluorescence intensity, 0.44-1.0%).