Modes of conformational changes of proteins adsorbed on a planar hydrophobic polymer surface reflecting their adsorption behaviors

Infrared spectra of hen egg white lysozyme and bovine serum albumin (BSA) adsorbed on a solid poly tris(trimethylsiloxy)silylstyrene (pTSS) surface in D2O solution were measured using attenuated total reflection (ATR) Fourier transform infrared spectroscopy. From the area and shape of the amide I' band of each spectrum, the adsorption amount and the secondary structure were determined simultaneously, as a function of adsorption time. We could show that the average conformation for all the adsorbed lysozyme molecules was solely determined by the adsorption time, and independent of the bulk concentration, while the adsorption amount increased with the bulk concentration as well as the adsorption time. These results suggest that lysozyme molecules form discrete assemblies on the surface, and that the surface assemblies grow over several hours to have a definite architecture independent of the adsorption amount. As for BSA, the extent of the conformational change was solely determined by the adsorption amount, regardless of the bulk concentration and the adsorption time. These differences in the adsorption properties of lysozyme and BSA may reflect differences in their conformational stabilities.     

Biodegradable Phosphorylcholine Polymer Hydrogels Cross‐Linked with Vinyl‐Functionalized Polyphosphate

A vinyl‐functionalized polyphosphate (PIOP) was synthesized by ring‐opening polymerization of 2‐isopropyl‐2‐oxo‐1,3,2‐dioxaphospholane and 2‐(2‐oxo‐1,3,2‐dioxaphosphoroyloxyethyl methacrylate) with triisobutylaluminum as an initiator. The number‐averaged molecular weight of the PIOP was 1.2 × 10⁴. The average number of vinyl groups in the PIOP is 2.20. Transparent hydrogels were prepared by the radical polymerization of 2‐methacryroyloxyethyl phosphorylcholine with PIOP as a cross‐linking reagent. These hydrogels may have many applications in the biomedical field because of their biodegradability and biocompatibility.

Synthetic route of PIOP.     

Effect of Static Magnetic Field on Photocatalytic Degradation of Methylene Blue over ZnO and TiO2 Powders

Magnetic field effects (MFEs) on photocatalytic degradation of methylene blue (MB) solution over ZnO and TiO₂ powders are investigated under static magnetic field up to 0.7 T with light irradiation by ultraviolet (UV) light emitting diode. The UV–visible-near-infrared spectrometer is used to monitor the MB concentrations. The positive MFE is observed for ZnO, while the negative MFE for TiO₂, and both MFEs are increased with the increase in the magnetic field applied. By increasing the settling time (the time interval between the preparation of MB solution and the powder dispersion into the MB solution), the photodegradation abilities under MFEs are decreased for both the catalysts. The cause of MFE is discussed in terms of dissolved oxygen in the MB solution and magnetic adsorption of the constituent molecules.     

Low-temperature growth of high-Tc superconducting films by plasma-enhanced metal-organic chemical vapor deposition

Plasma-enhanced MOCVD in which metal-organic compounds are sublimated directly into the growth chamber is studied for the first time as a new low-temperature process for growing superconducting YBa₂Cu₃O-_-x thin films. Y(THD)₃, Ba(THD)₂, Cu(THD)₂ and oxygen are used as metal sources and oxydizing agent. Emission spectroscopy reveals that activated metal-organic compounds and activated oxygen species are present during film growth. Superconducting YBa₂Cu₃O_7-x films whose zero-resistivity temperature are 50 K and 82 K are grown at 550°C and 600°C.     

Simultaneous Determination of Pyridine-Triphenylborane Anti-Fouling Agent and Its Degradation Products in Artificial Seawater by CZE

We developed a CZE method for simultaneous determination of pyridine-triphenylborane (PTPB) anti-fouling agent and its degradation products such as diphenylborinic acid (DPB), phenylboronic acid (MPB), and phenol in artificial seawater (ASW) with no extraction procedure. The ASW samples, in which 20 % (v/v) acetonitrile was added, were injected directly into the capillary using vacuum injection. As the background electrolyte, 60 mM sodium tetraborate adjusted to pH 9.8 was used. The LODs (S/N = 3) for PTPB, DPB, MPB, and phenol were, respectively, 55, 78, 126, and 30 μg L^?1. The RSDs (n = 4) for analytes listed above were in the respective ranges of 2.7–5.7, 0.68–6.1, and 0.69–1.1 % for the peak area, peak height, and migration time. Simple degradation experiments were conducted to verify the usefulness of the proposed method. The PTPB samples dissolved in ASW were put in the open air, and rooms with and without light. The sample solutions were analyzed over time. We inferred that PTPB in ASW was more degraded by photolysis than by hydrolysis. The proposed CZE method has been demonstrated as a useful tool to elucidate the PTPB degradation process and its degradation products in ASW.     

Detailed Analysis of the Crystal Structures and Magnetic Properties of a Dysprosium(III) Phthalocyaninato Sextuple-Decker Complex: Weak f–f Interactions Suppress Magnetic Relaxation

In the research field of single-molecule magnets (SMMs), lanthanoid–lanthanoid interactions, so-called f–f interactions, are known to affect the SMM properties, although their magnitudes are small. In this article, an SMM with very weak f–f interactions is reported, and the effects of the interactions on the SMM properties are discussed. X-ray structural analysis of the Dy^III-Cd^II-phthalocyaninato sextuple-decker complex (Dy₂Cd₃) reveals that the intramolecular Dy−Dy length in Dy₂Cd₃ is more than 13 Å, which is longer than the intermolecular Dy−Dy length. Even though the two Dy^III ions are far apart, intermolecular ferromagnetic dipole–dipole interactions are observed in Dy₂Cd₃. From detailed analysis of ac magnetic susceptibilities, quantum tunneling of the magnetization (QTM) in Dy₂Cd₃ is partially suppressed owing to the existence of very weak Dy−Dy interactions. Our results show that even very weak Dy−Dy interactions act as a dipolar bias, suppressing QTM.     

Potassium-ion-selective sensing based on selective reflection of cholesteric liquid crystal membranes

It is well-known that cholesteric liquid crystals have an optical property, selective reflection, due to changes in the pitch of their helical structure. This unique property of cholesteric liquid crystals can be used to attain a visual sensing system showing color changes as the detection signal. In this paper, we report a visual sensing membrane comprising cholesteric liquid crystals, in which a 15-crown-5 derivative was incorporated as ion recognizing sites, for K⁺ in aqueous solution. The resulting CLC membrane showed a shift of the reflection peak sensitive to K⁺ in water. We have also designed polymer-dispersed liquid crystal membranes that showed ion-selective reflection peak shifts with improved response time.     

Tentative Comparison of Tube Radial Distribution Chromatography and CZE

Tube radical distribution chromatography (TRDC) uses an untreated open tubular capillary tube and a ternary mixture of solvents (water and hydrophilic/hydrophobic organic solvents) as a carrier solution. A model analyte mixture comprising 1-naphthol, 1-naphthoic acid, 1-naphthalenesulfonic acid, 2,6-naphthalenedisulfonic acid, and 1,3,6-naphthalenetrisulfonic acid was examined by the TRDC and capillary zone electrophoresis (CZE) systems that comprised mainly a capillary tube and a detector. In the TRDC system the elution order of analytes could be changed by altering the component ratios of the solvents, whereas in the CZE system the elution order was changed by altering the electroosmotic flow direction. The experimental data obtained provide clues about the features and utility of TRDC as a new separation method.     

Acceleration of Proliferative Response of Mouse Fibroblasts by Short-Time Pretreatment with Polyphenols

Under the hypothesis that photo-irradiated proanthocyanidin could accelerate wound healing through reactive oxygen species (ROS) formation, we examined the effect of proanthocyanidin on 3T3-L1 mouse fibroblasts with or without photo-irradiation. As a result, irrespective of presence or absence of photo-irradiation, only 1 min exposure of the cells to proanthocyanidin resulted in accelerated proliferation of the cells in a concentration-dependent manner. Similarly to proanthocyanidin, 1 min pretreatment with catechin, caffeic acid, and chlorogenic acid accelerated the proliferative response, but gallic acid, epicatechin gallate, epigallocatechin, and epigallocatechin gallate failed. If incorporated active ingredient such as proanthocyanidin for such a short time as 1 min accelerates the proliferation response, a bioassay was conducted by utilizing antioxidant potential of proanthocyanidin. That is, intracellular oxidation of 2′,7′-dichlorodihydrofluorescin induced by H₂O₂ was significantly inhibited when the cells were pretreated with proanthocyanidin for 1 min, suggesting that incorporated proanthocyanidin into the cells exerted antioxidant effect. This was also supported by a liquid chromatography/mass spectrometry analysis in which incorporation of proanthocyanidin components such as catechin monomers and dimers into the cells within 1 min was confirmed. These results suggest that active polyphenolic compounds such as proanthocyanidin, catechin, caffeic acid, and chlorogenic acid incorporated into the cells in such a short time as 1 min could accelerate the proliferative response of the cells.