CHANGES IN cAMP AND cGMP CONCENTRATION, BIREFRINGENT FIBRILS AND CONTRACTILE ACTIVITY ACCOMPANYING UV AND BLUE LIGHT PHOTOAVOIDANCE IN PLASMODIA OF AN ALBINO STRAIN OF Physarum polycephalum

Abstract— Photoavoidance by plasmodia of an albino strain of Physarum polycephalum was studied. When the organism was irradiated locally, the protoplasm moved away from the irradiated region. The action spectrum for this avoidance showed three peaks at about 260, 370 and 460 nm. The organism was about one hundred times as sensitive to far UV as to near UV and blue light, and high intensity far-UV caused the gelation of the protoplasm. Irradiation with UV or blue light increased the mean level or the amplitude of oscillation in intracellular cAMP and cGMP concentrations. Upon UV irradiation, birefringent fibrils, presumably microfilaments of F-actin, became thick and numerous, and the plasmodial strand generated a strong tensile force. It is postulated that UV or blue light brings about an increased concentration of cyclic nucleotides which leads to an enhanced local development of contractile fibrils which squeeze protoplasmic sol from the area, resulting in photoavoidance.     

Diastereoselective cyclization of a dithienylethene switch through single crystal confinement

Upon UV irradiation of the hydrogen-bond confined crystal state of a dithienylhexafluorocyclopentene with (R)-N-phenylethylamide substituents, the photochemical cyclization reaction proceeds diastereoselectively to form the coloured, closed-ring isomer with 97% de.     

Control of surface wettability and photomicropatterning with a polymorphic diarylethene crystal upon photoirradiation

A photochromic diarylethene crystal of 1,2‐bis(2‐methyl‐6‐nitro‐1‐benzothiophen‐3‐yl)perfluorocyclopentene ( 1 a ) was found to undergo a thermodynamic phase transition at 180 °C to form a needle‐like crystal, designated as 1 a‐γ . The phase transition involves melting of the initial α‐crystal and growth of the γ‐crystal. The phase transition temperature decreased with the presence of the closed‐ring isomer ( 1 b ) in the crystal because of the decrease in the melting temperature. Upon irradiation with ultraviolet (UV) light, compound 1 a in the α‐crystal was converted into 1 b to an extent of 20 %. Consequently, the α‐crystal containing 20 % of 1 b underwent the phase transition accompanied by melting of the crystal and growth of the γ‐crystal even at 170 °C. Photomicropatterning by the phase transition upon irradiation with UV light using a photomask, followed by heating at 170 °C, was successfully accomplished with a resolution in the microcrystalline pattern of about 20 μm. The contact angle with water on the γ‐microcrystalline phase on a glass substrate was larger than that on the α‐microcrystalline phase by 20°. This can be ascribed to a difference in the roughness of the surface. Furthermore, the γ‐microcrystal was also found to be formed upon heating an amorphous film of 1 a in poly(methyl methacrylate) for 2 min at 130 °C. The crystallized area exhibited a higher water contact angle than the amorphous area. Upon irradiation of the amorphous film with UV light, such crystallization did not take place because of the impurity effect of 1 b in 1 a . Photomicropatterning by the crystallization in the polymer showed a pattern with a higher resolution of about 4 μm, which was much better than that of the neat crystal. This photopatterning process represents a useful tool for controlling the surface wettability in relevant applications.     

Limits of detection and selectivity coefficients of a PVC-based anion-selective electrode

A PVC-based anion-selective electrode was constructed with use of Capriquat as ion-exchanger. Experimental data were in good agreement with E = E(0) - (RT/F)ln(C + radicalC (2) + A (x))/2. The parameter A(x) governs the limit of detection. It was experimentally shown that A(x) was related to the selectivity coefficient K(xy) by K(xy) = A(y)/A(x).     

Plasma-polymerized membrane electrode for the determination of dextromethorphan and dimemorfan

Ion-selective electrodes (ISEs) responsive to the antitussives dextromethorphan and dimemorfan were constructed by the fixation of an ion-exchanger, ammonium tetraphenylborate, on a Millipore membrane by means of a plasma-polymerization technique. The electrodes showed a Nernstian response over the range of 10(-5)-10(-2) M dextromethorphan and dimemorphan, and the working pH range was 5-7. The interference from common cations such as Na+, K+ and Ca2+ was negligible but some organic cations interfered weakly. The electrodes were applied successfully for the determination of the drugs in pharmaceutical preparations.     

Design and construction of glutamine binding proteins with a self-adhering capability to unmodified hydrophobic surfaces as reagentless fluorescence sensing devices

The chemically and genetically remodeling of proteins with ligand binding specificities can be utilized to synthesize various protein-based microsensors for detecting single biomolecules. Here, we describe the construction and characterization of fluorophore-labeled glutamine binding proteins (QBP) and derivatives coupled to the independently designed hydrophobic polypeptide (E12) that can adhere onto solid surfaces via hydrophobic interactions. The single cysteine mutant (N160C QBP) modified with the three environmentally sensitive fluorescent dyes (IAANS, acrylodan, and IANBD ester) showed increased changes in fluorescence intensity induced by glutamine binding. The use of these conjugates as reagentless fluorescence sensors enables us to determine the glutamine concentrations (0.1-50 microM) in homogeneous solution. The fusion of N160C QBP with E12, (Gly4-Ser)n spacers (GSn), and IANBD resulted in the novel fluorescence sensing elements having an adhering capability to hydrophobic surfaces of unmodified microplates. In ELISA and fluorescence experiments for the microplates treated with a series of the conjugates, IANBD-labeled N160C QBP-GS1-E12 displayed the best reproducibility in adhesion onto the hydrophobic surfaces and the precise correlation between fluorescence changes and glutamine concentrations. The performance of the biosensor-attached microplate for glutamine titrations demonstrated that the hydrophobic interaction of E12 with solid surfaces is useful for effective immobilization of proteins that need specific conformational movements in recognizing particular biomolecules. Therefore, the technique using E12 as a surface-linking domain for protein adhesion onto unmodified substrates could be applied effectively to prepare microplates/arrays for a wide variety of high-throughput assays on chemical and biological samples.     

Mechanics of adhesive joints

Summary Taking into consideration both the pulling and bending actions of the external force, the differential equations for bending of a partly attached tape in a peeling test have been derived. The equations relating the peeling load to the adhesive force were derived under the assumption that the peeling may proceed step by step from the attached end when the adhesive force is overcome by either the tensile stress along the interface (shearing peeling) or that which is perpendicular to the interface (tensile peeling). To verify the validity of the obtained equations, the dependence of the peeling load P on the angle between the direction of the action of the load and the adhering surface has been investigated using plasticized polymer films. In view of the elementary mechanics, the results were satisfactory, while a modification was attempted by introducing the stress concentration factor.