Potentiometric and spectroscopic studies of the reaction between trypsin and its inhibitors on chemically modified solid surfaces

The potential of a titanium metal electrode modified with trypsin changes as a result of the complex formation reaction between trypsin and its inhibitor, aprotinin, dissolved in the solution. A similar potential change in the opposite direction occurs by the reaction between aprotinin-modified electrode and trypsin in the solution. The induced changes in both cases depend on the pH of the solution, showing the maximum change at pH = 9.5. The potentiometric response of the trypsin-modified electrode for the consecutive addition of aprotinin and proflavine proves that trypsin bound on the solid surfaces reacts with aprotinin much more strongly than with proflavine. This result is fully consistent with the spectroscopically observed behavior of a trypsin-modified quartz plate against these inhibitors. The surface coverage of trypsin on the quartz plate is also determined by a near-ultraviolet absorption measurement.     

Transmission electron microscopy of fine aromatic hydrocarbon particles

Fine perylene and pyrene particles were produced by evaporation in helium gas. The particles were sensitive to electron beam radiation. The pyrene particles sublimed under observation. These difficulties were cleared up by reducing electron beam exposure and sandwiching a specimen between two Formvar films. The fine perylene particles were rectangular or hexagonal plates about 50nm thick. The size was about 200-2000nm. The fine pyrene particles were polymorphic with a size of about 300-2000nm. The crystal forms of the perylene and pyrene particles were determined from the electron diffraction patterns to be alpha-perylene and pyrene I, respectively.     

Experimental observation of vertically polarized transverse dust-lattice wave propagating in a one-dimensional strongly coupled dust chain

Externally driven, vertically polarized transverse dust-lattice waves were observed in a one-dimensional strongly coupled dust chain levitated in the plasma-sheath boundary of a dc argon plasma at low gas pressure around 5 mtorr. Real and imaginary parts of the complex wave number were measured in the experiments. The experimental result clearly shows that the observed transverse dust-lattice wave propagates as a backward wave, which is in good agreement with the theoretical prediction.     

On-chip electrochemical measurement of beta-galactosidase expression using a microbial chip

[small beta]-Galactosidase expression in a small number of Escherichia coli cells has been measured in real time with an electrochemical sensor chip. E. coli cells were embedded using collagen gel within a micropore which was microfabricated onto a chip. The activity of the expressed [small beta]-galactosidase was determined using p-aminophenyl [small beta]-d-galactopyranoside (PAPG) as a substrate.     

Fabrication of vertically and unidirectionally oriented polypeptide assemblies on self-assembled monolayers by stepwise polymerization

A polypeptide assembly prepared by stepwise polymerization on a self-assembled monolayer consisting of amino-alkanethiol and dialkyl disulfide oriented vertically and unidirectionally to the surface.     

In‐situ monitoring of a film preparation process for hydroxypropyl cellulose cast from isotropic aqueous solution using microdielectrometry

Solid cast films with polydomain textures were prepared on a glass substrate with transparent interdigitated electrodes from an isotropic aqueous solution of hydroxypropyl cellulose via its liquid crystalline phase under the sinusoidal electric field with small amplitude and frequency of 0.05 V µm^?1 and 10⁵ Hz, respectively. The process was monitored using microdielectrometry as well as polarised optical microscopy. The apparent dielectric constant ε_r′ and loss factor ε_r″ sensitively changed with time depending on the process conditions. On the other hand, the logarithmic relation between ε_r″ and ε_r′ showed a single curve, when they were normalised by an effective portion of the electrostatic energy density estimated using each solid‐film thickness. The conversion to the solid film was estimated during the process based on the concentration dependences of ε_r′ and ε_r″. Characteristic times were reported for the onset of the biphasic phase, fully developed cholesteric phase and termination of the process.     

Effect of swirling flow on unburned ratio and nitrogen oxide concentration in a spray combustion system

The effect of swirling flow on the unburned ratio and NO concentration in exhausted gas was studied for slurry [coal-water mixture (CWM)] spray combustion with variations of swirl numbers. A numerical analysis for CWM combustion was performed for axisymmetric flow in a cylindrical geometry. First, to check the performance of three previous k-ε turbulence models modified with swirling flow, velocity components of isothermal swirling jets were measured by laser-Doppler anemometry (LDA) and compared with predicted results. The two modified models gave more reliable results than the conventional one. Next, as the swirl number could not be estimated by the angular momentum derived from the vane angle of the circular swirler, the reduction rate of the tangential momentum flux through the tube of the circular swirler was measured and calculated. Both measured and predicted results showed that when the swirl number S′ given by the vane angle was 2.0, the effective swirl number S_eff decreased by about 60% to S′. To take the results mentioned above into consideration, effects of swirl number on both the exhausted NO concentration and unburned ratio were investigated. The predicted unburned ratio showed good agreement with the experimental results. Both experimental and calculated results showed that the optimum operating conditions controlling the exhausted NO concentration and unburned ratio in this spray combustion system were obtained when the swirl number S_eff was about 0.5.     

Miscibility and volume changes of mixing in the polystyrene/poly(2-chlorostyrene) blend system

The specific volume-temperature relationships of polystyrene, poly(2-chlorostyrene), and their polymer blends as well as the volume change of mixing Δv_m of the blends were obtained in the liquid state by dilatometry. The equation of state parameter and the molecular parameter of each homopolymer and blends were determined according to the lattice fluid theory of Sanchez and Lacombe. The experimental Δv_m obtained agreed quite well with that predicted from theory, and the enthalpy of mixing ΔH_m was also predicted using the pair molecular parameter. These two values were negative, indicative of miscibility of polystyrene and poly(2-chlorostyrene) in the liquid state. The absolute values of Δv_m and ΔH_m were about twice those for polystyrene and poly(phenylene oxide) blend, suggesting a specific interaction between the two polymers.