Energetics and optical properties of carbon impurities in rutile TiO2

Titanium dioxide is one of the most promising materials for many applications such as photovoltaics and photocatalysis. Non-metal doping of TiO₂ is widely used to improve the photoconversion efficiency by shifting the absorption edge from the UV to visible-light region. Here, we employ hybrid density-functional calculations to investigate the energetics and optical properties of carbon (C) impurities in rutile TiO₂. The predominant configurations of the C impurities are identified through the calculated formation energies under O-poor and O-rich growth conditions. Under the O-poor condition, we find that C occupying the oxygen site (C_O) is energetically favorable for Fermi-level values near the conduction band minimum (n-type TiO₂), and acts as a double acceptor. Under the O-rich condition, the C_i–V_Ti complex is energetically favorable, and is exclusively stable in the neutral charge state. We also find that interstitial hydrogen (H_i) can bind to C_O, forming a C_O–H_i complex. Our results suggest that C_O and C_O–H_i are a cause of visible-light absorption under oxygen deficient growth conditions.

The substitutional C on O site and its complex with H are a cause of visible-light absorption in rutile TiO₂.     

Bioactivities of Jc‐SCRIP,a Type 1 Ribosome‐Inactivating Protein from Jatropha curcas Seed Coat

In this study, a type 1 RIP, designated as Jc‐SCRIP, was first isolated from the seed coat of Jatropha curcas Linn. It was purified by ammonium sulfate precipitation and chromatography on DEAE‐Sephacel? and CM‐cellulose columns. Purification fold of Jc‐SCRIP increased 113.8 times, and the yield was 1.13% of the total protein in the final step. It was shown to be a monomeric glycoprotein with a molecular mass of 38 938 Da, as determined by MALDI‐TOF/MS. It exhibited hemagglutination activity and possessed strong N‐glycosidase activity. The antimicrobial activity of Jc‐SCRIP was tested against nine human pathogenic bacteria and one fungus; the most potent inhibitory activity was against Staphylococcus epidermidis ATCC 12228, with minimum inhibitory concentration value of 0.20 μm . Jc‐SCRIP demonstrated in vitro cytotoxicity against human breast adenocarcinoma cell line (MCF‐7), a colon adenocarcinoma (SW620), and a liver carcinoma cell line (HepG2), with IC₅₀ values of 0.15, 0.25, and 0.40 mm , respectively. The results suggested that Jc‐SCRIP may be a potential natural antimicrobial and anticancer agent in medical applications.     

Stilbenoids from Gnetum macrostachyum Attenuate Human Platelet Aggregation and Adhesion

Platelets play a critical role in pathogenesis of cardiovascular disorders and strokes. The inhibition of platelet function is beneficial for the treatment and prevention of these diseases. The phytochemical investigation of stilbenoids from Gnetum macrostachyum Hook. f. led to the isolation of trans‐resveratrol (1), isorhapotigenin (2), gnetol (3), bisisorhapontigenin B (4), gnetin C (5), parvifolol A (6), latifolol (7) and gnetuhainin C (8). The isolated stilbenoids were evaluated for in vitro antiplatelet activities via agonist‐induced platelet aggregation and static platelet‐collagen adhesion assays using washed human platelets. Compounds 1, 2 and 3 were active in the inhibition of arachidonic acid (AA)‐induced platelet aggregation. Compound 2 and its dimer, compound 4, were the most active stilbenoids in thrombin‐induced platelet aggregation. Moreover, compounds 4, 5 and 6, tended to be more potent than monomeric and trimeric stilbenoids in a human platelet‐collagen adhesion assay under static conditions. This is the first report of the antiplatelet activity of stilbenoids isolated from G. macrostachyum. Copyright © 2012 John Wiley & Sons, Ltd.     

Detection and discrimination of WU/KI polyomaviruses by real-time PCR with melting curve analysis

WU and KI polyomaviruses are novel viruses of the Polyomaviridae family, which have been identified recently in respiratory secretions from patients with acute respiratory tract infection. Their potential role in respiratory disease is still unclear and requires additional investigation. To facilitate further studies and diagnosis, a real-time PCR with melting curve analysis was optimized and evaluated to detect WU and KI polyomaviruses. Primers specific for the VP1 gene were designed from regions conserved among WU and KI polyomaviruses which provided amplification products of 198 and 231bp corresponding to WU and KI, respectively and thus yielded a difference in melting temperature (T(m)) between WU and KI polyomaviruses. The assay proved highly specific for WU and KI polyomaviruses as no cross amplification was detected with other respiratory viruses or human genomic DNA. The assay was also highly sensitive with a detection limit as low as 10copies/muL for both WU and KI polyomaviruses. The performance of the real-time PCR assay was evaluated in terms of amplification efficiency (92%). Finally, the assay was validated using DNA extracted from clinical respiratory specimens for WU and KI polyomaviruses and the results were confirmed by direct nucleotide sequencing. The results obtained by melting curve analysis were in perfect agreement with nucleotide sequencing. In conclusion, this method is advantageous because it is rapid, specific, sensitive, reproducible, accurate, cost-effective and thus, would be feasible and attractive for large-scale analysis aimed at investigating the clinical role of WU and KI polyomaviruses.     

IL-6 regulates stress-induced REX-1 expression via ATP-P2Y1 signalling in stem cells isolated from human exfoliated deciduous teeth

Objective

To investigate the relationship between ATP and IL-6 in mechanical stress-induced REX-1 expression in SHEDs.

Methods

Cells were stimulated with mechanical stress (0–2.5 g cm⁻²), IL-6 (0.1–5 ng/ml), or ATP (10–100 μM) for 2 h in serum-free media. IL-6 and REX-1 expression was examined by qualitative and quantitative polymerase chain reaction. ATP release was measured using a bioluminescence assay. The molecular mechanisms of the signalling pathways were investigated using chemical inhibitors.

Results

Mechanical stress induced IL-6 and REX-1 mRNA expression and ATP release. JAK inhibitor I inhibited the increase in REX-1 expression and ATP release but not IL-6 induction. Furthermore, suramin inhibited the upregulation of REX-1 mRNA expression but not ATP release. Exogenous IL-6 promoted both ATP release and REX-1 expression. The IL-6-induced REX-1 expression was attenuated by a P2Y1-specific receptor antagonist. Moreover, REX-1 expression was upregulated in a dose-dependent manner by the addition of ATP or a P2Y1 agonist. This inductive effect was abolished by the P2Y1-specific receptor antagonist.

Conclusions

ATP-P2Y1 signalling is involved in IL-6-regulated stress-induced REX-1 expression in SHEDs. These results imply the participation of mechanical stress, IL-6, and ATP in regulating the expression of REX-1, a pluripotent stem cell marker.     

Inhibitory effects of crude extracts from some edible Thai plants against replication of hepatitis B virus and human liver cancer cells

Background

Edible plants such as Cratoxylum formosum (Jack) Dyer, Curcumin longa Lin, Momordica charantia Lin and Moringa oleifera Lam have long been believed in Thai culture to relieve ulcers and the symptoms of liver disease. However, little is known about their anti-liver cancer properties and antiviral activity against hepatitis B virus (HBV). The aim of this study was to investigate the anti-liver cancer and anti-HBV activities of crude extracts from these edible plants on human liver cancer cells.

Methods

Plant samples were prepared and extracted using buffer and hydro-alcoholic solvents. The MTT assay was performed to investigate the effects of the plant extracts on the cell viability of HepG2 cells. The inhibitory effect on replication of HBV was analysed by determining the level of HBV covalently closed circular DNA (cccDNA) in transiently transfected HepG2 cells with the DNA expression plasmid of the HBV genome using a quantitative real-time PCR.

Results

Buffer and hydroalcoholic extracts from C. formosum (leaf) reduced cell viability of HepG2 cells and they also inhibited HBV cccDNA. Crude extracts from C. longa (bulb) in both solvents did not have any cytotoxic effects on the HepG2 cells, but they significantly decreased the level of HBV cccDNA. Buffer extracts from the leaves of M. charantia and the fruits of M. oleifera showed to have anti-HBV activity and also a mild cytotoxicity effect on the HepG2 cells. In addition, leaves of M. Oleifera extracted by hydroalcoholic solvent drastically decreased the level of cccDNA in transiently transfected HepG2 cells.

Conclusion

Some crude extracts of edible plants contain compounds that demonstrate anti-liver cancer and anti-HBV activities.