Effects of various ginkgo biloba extracts and proanthocyanidin on hepatic cytochrome P450 activity in rats

In previous papers, we showed that Ginkgo biloba extract (GBE) induced hepatic cytochrome P450 (CYP) activity, in particular pentoxyresorufin O-dealkylase (PROD; corresponding to CYP2B type) in rats, and that GBE influenced the efficacy of co-administered drugs. In this study, to clarify the nature of the induction, we examined the effects of GBE samples from different sources and some major constituents of GBE on rat hepatic CYP in vitro and in vivo. In the study in vitro, eight GBE samples dose-dependently inhibited PROD activity in microsomes prepared from GBE-treated rats, and the inhibitory ratio correlated well with the content of proanthocyanidin in the GBE samples. Moreover, among six GBE constituents examined, proanthocyanidin markedly inhibited the PROD activity. However, administration of two GBE extracts with different proanthocyanidin contents to rats induced hepatic CYP activity, including PROD, to similar extents, and proanthocyanidin alone did not induce PROD activity. Furthermore, GBE samples extracted with both acetone-water and ethanol-water showed similar induction of CYPs in rats in vivo. These results suggest that most GBE samples available in Japan induce CYPs in rats regardless of the preparation method of the GBE, and that proanthocyanidin is not responsible for the induction. Further studies will be necessary to identify the constituent(s) of GBE involved in the induction of CYPs in vivo.     

Family 3 beta-glucosidase from cellulose-degrading culture of the white-rot fungus Phanerochaete chrysosporium is a glucan 1,3-beta-glucosidase

The substrate specificity of an extracellular beta-glucosidase (BGL) from cellulose-degrading culture of the white-rot fungus Phanerochaete chrysosporium was investigated, using a variety of compounds with beta-glucosidic linkages. Amino acid sequencing data for the purified BGL showed that the enzyme is identical to the glycoside hydrolase (GH) family 3 BGL of the same fungus previously reported [Li, B. and Renganathan, V, Appl. Environ. Microbiol., 64, 2748-2754 (1998)]. The BGL can hydrolyze both cellobiose and cellobionolactone, but cellobionolactone was hydrolyzed very much more slowly than cellobiose. Moreover, cellobionolactone inhibited cellobiose hydrolysis by the BGL, suggesting that this enzyme cannot cooperate with cellobiose dehydrogenase (CDH) in cellulose degradation by P. chrysosporium. In addition to cellobiose, BGL utilized various glucosyl-beta-glucosides, such as sophorose, laminaribiose and gentiobiose, as substrates. Among the four substrates, laminaribiose (beta-1,3-glucosidic linkage) was hydrolyzed most effectively. Moreover, the hydrolytic rate of laminarioligosaccharides increased proportionally to the degree of polymerization (DP), and the activity of BGL even towards laminarin with an average DP of 25 was similar to that towards laminaripentaose (DP 5). Therefore, we conclude that the extracellular BGL from P. chrysosporium is primarily a glucan 1,3-beta-glucosidase (EC 3.2.1.58), which might play a role on fungal cell wall metabolism, rather than a beta-glucosidase (EC 3.2.1.21), which might be involved in the hydrolysis of beta-1,4-glucosidic compounds during cellulose degradation.     

A theoretical study of molecular conduction: IV. A three-terminal molecular device

We discuss the features of a three-terminal molecular device and the control of electric current using a gate terminal. We introduce a capacitance model to investigate the effect of the gate terminal that could reduce to a two-terminal molecule for a very small gate capacitance. Therefore, this capacitance model can be used in the framework of ordinary ab initio quantum chemical methods. We show the effect of the gate terminal analytically using a simple Hückel method. Moreover, we used our capacitance model with a nonequilibrium Green's function (NEGF)-based Hartree-Fock (HF) approach to study the gate control features of the benzenedithiolate molecule, and we show that the current through the molecule can be modulated by the gate voltage in the case of a high gate control parameter. We also discuss the molecule's response to the applied bias voltage. It is found that the molecular charging effect has a strong influence on the behavior of molecular-based electronic devices.     

Antioxidant and anticancer properties of metalloporphyrins embedded in liposomes

Reactive oxygen species (ROS) are implicated in many disease such as inflammation, arteriosclerosis, cancer. Therefore, a water-soluble cationic metalloporphyrins with SOD activity are studied widely as antioxidant drugs. Further, liposomes are applied to drug delivery system (DDS) as drug carriers and investigated for example disposition and stability. We designed PEG modified liposomes for avoiding reticuloendothelial system (RES) and embedded cationic metalloporphyrins for DDS, evaluated antioxidant and anticancer property. Preservation of these particle size measured DLS in an in vitro system, in order to simulate in vivo conditions of flow. Result of this measurement, we found Pluronic F-68/ liposomes have a long circulation property, and avoid fusion with plasma protein. SOD activity was determined by the stopped-flow analysis and cytochrome c assay, which allowed the evaluation of k(cat) and IC(50) for the reaction with a superoxide anion radical (.O(2)(-)). Anti cancer property was measured by cell viability test. We found that F-68/ liposomes were the most effective catalyst as antioxidant and anticancer. These results revealed that porphyrin-embedded PEG-liposomes had the property of long circulation in blood and that this compound was effective as a SOD model compound with a drug carrier capacity.     

Large area thin film Si module

An initial efficiency of 14.1% (J_sc=13.6 mA/cm², V_oc=1.392 V, FF=74.3%) has been achieved for a-Si/transparent interlayer/poly Si solar cell (total area of 1 cm²). Both a-Si and crystalline Si films were fabricated by plasma chemical deposition at low temperature. The short circuit current was enhanced by the introduction of a transparent intermediate layer. An initial aperture efficiency of 11.7% has been achieved for 910×455 mm² a-Si/poly Si integrated solar cell submodule, where the laser-scribing techniques were applied for series interconnections. The results of our first run of 266 submodules in our pilot plant showed the average efficiency of 11.2%, which is applicable for mass production.     

Transparent thermoplastic resin with electron beam cross‐linking

The mechanical, thermal and optical properties of a transparent thermoplastic resin which is based on non‐crystalline nylon with cross‐linking agents were improved by electron beam (EB) irradiation cross‐linking. When the EB irradiation power was increased, the yield stress improved by 34% and the glass transformation temperature increased from 116 to 165°C. Transformation from the brittle to the ductile state was observed by the dependence of a strange elastic module on the temperature and EB irradiation power. Above the glass transformation temperature, an optical element produced using this resin could maintain its shape. The birefringence decreased when the EB irradiation power was increased. The decrease of the birefringence was dependent on the initial birefringence value before EB cross‐linking. The molecular orientation was relaxed by EB cross‐linking. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Sizing of single globular DNA molecules by using a circular acceleration technique with laser trapping

We describe a method for in situ sizing individual huge DNA molecules by laser trapping. Single DNA molecules are reversibly transformed, without mechanical fragmentation of fragile huge-sized DNA, from their random coil state into their globular state induced by condensing agents poly(ethylene glycol) and Mg(2+). With the use of a globular DNA molecule folded by condensation, the critical velocity of the circularly accelerated single globular DNA molecule by laser trapping was found to be proportional to the size of the DNA. Yeast, Saccharomyces cerevisiae, chromosome III (285 kbp) was successfully sized (281 +/- 40 kbp) from a calibration curve scaled using lambda, T4, and yeast chromosome VI (48.5, 166, and 385 kbp, respectively). The use of critical velocity as a sizing parameter makes it possible to size single DNA molecules without prior conformational information, i.e., the radius of a single globular huge DNA molecule as a nanoparticle. A sized single globular DNA molecule could be trapped again for subsequent manipulation, such as transportation of it anywhere. We also investigated a possibility of reusing the globular DNA molecules condensed by PEG and Mg(2+) for PCR and found that PCR efficiency was not deteriorated in the presence of the condensation agents.     

How metal ions affect amyloid formation: Cu2+- and Zn2+-sensitive peptides

The common feature of proteins involved in many neurodegenerative diseases is their ability to adopt at least two different stable conformations. The conformational transition that shifts the equilibrium from the functional, mostly partially alpha-helical structure, to the beta-sheet rich amyloid can be triggered by numerous factors, such as mutations in the primary structure or changes in the environment. We present a set of model peptides that, without changes in their primary structure, react in a predictable fashion in the presence of transition metal ions by adopting different conformations and aggregate morphologies. These de novo designed peptides strictly follow the characteristic heptad repeat of the alpha-helical coiled-coil structural motif. Furthermore, domains that favor beta-sheet formation have been incorporated to make the system prone to amyloid formation. As a third feature, histidine residues create sensitivity towards the presence of transition metal ions. CD spectroscopy, ThT fluorescence experiments, and transmission electron microscopy were used to characterize peptide conformation and aggregate morphology in the presence of Cu2+ and Zn2+. Furthermore, the binding geometry within peptide-Cu2+ complexes was characterized by electron paramagnetic resonance spectroscopy.     

Measurements of Singlet Oxygen‐Quenching Activity of Vitamin E Homologs and Palm Oil and Soybean Extracts in a Micellar Solution

Recently, a new assay method that can quantify the singlet oxygen‐absorption capacity (SOAC) of antioxidants (AO) and food extracts in homogeneous organic solvents has been proposed. In the present study, second‐order rate constants (k_Q) for the reaction of singlet oxygen (¹O₂) with vitamin E homologs (α‐, β‐, γ‐, and δ‐tocopherols [Toc] and α‐, β‐, γ‐, and δ‐tocotrienols [Toc‐3]) were measured in an aqueous Triton X‐100 (5.0 wt%) micellar solution (pH 7.4). Toc‐3 showed k_Q values larger than those of Toc in a micellar solution, although Toc and Toc‐3 showed the same k_Q values in a homogeneous solution. Similar measurements were performed for 5 palm oil extracts 1–5 and one soybean extract 6, which contained different concentrations of Toc, Toc‐3, and carotenoids. It has been clarified that the ¹O₂‐quenching rates (k_Q) (that is, the relative SOAC value) obtained for extracts 3–6 may be explained as the sum of the product of the rate constant () and the concentration ([AO‐i]/100) of AO‐i contained. The UV–vis absorption spectra of Toc and Toc‐3 were measured in a micellar solution and chloroform. The results obtained demonstrated that the k_Q values of AO in homogeneous and heterogeneous solutions vary notably depending on (1) polarity (dielectric constant [ε]) of the reaction field between ¹O₂ and AO, (2) the local concentration of AO, and (3) the mobility of AO in solution. The results suggest that the SOAC method is applicable to the measurement of ¹O₂‐quenching activity of general food extracts in a heterogeneous micellar solution.     

Inward Migration of Glass‐Modifier Cations During Heat Treatment Under an N2 Atmosphere

An Na⁺/Ca²⁺‐deficient layer is observed to form on the glass surface region up to a depth of hundreds of nanometers when a soda‐lime‐silicate glass is heat treated under an N₂ atmosphere near its glass‐transition temperature. The measurements were performed using X‐ray photoelectron spectroscopy with C₆₀‐ion sputtering (C₆₀‐XPS) and dynamic secondary‐ion mass spectrometry (D‐SIMS) with consideration of the mass and charge balances. The increase in the amount of hydrogen is substantially less than the decrease in the total charge due to the loss of modifier cations in the Na⁺/Ca²⁺‐deficient layer; furthermore, the oxygen concentration in this layer is lower than the bulk value, suggesting that the silanol groups in the surface layer of the glass are dehydrated. A high‐concentration layer of Ca²⁺ is also confirmed in the dehydration layer of the glass heat treated under an N₂ atmosphere, suggesting that Na⁺ and Ca²⁺ ions migrate inward into the glass via an ion‐exchange reaction with protons, which migrate toward the surface from the bulk. We also confirmed that a thicker Na⁺/Ca²⁺‐deficient layer is formed on glass surfaces with higher water content. Our results suggest that the dehydration of the silanol groups is the driving force of the inward migration of Na⁺ and Ca²⁺ ions.