Certification of a pure reference material for the ginsenoside Rg 1

A pure certified reference material (CRM) for the ginsenoside Rg ₁ was prepared from roots of Panax ginseng by extraction and separation of ginsenosides. The mass fraction of the main component (ginsenoside Rg ₁ ) in the reference material was determined and its uncertainty was assessed from various input quantities, such as organic impurities, residual moisture, residual solvent, ash, and insoluble matters. To measure these input quantities, HPLC/CAD, Karl Fischer (KF) coulometry, gravimetry, and GC/FID were used. Homogeneity and long-term stability of the reference material are discussed. The certified mass fraction of Rg ₁ in the reference material is 0.974 ± 0.006 (k = 2) with a shelf life of 1 year.     

Human telomerase catalytic subunit (hTERT) suppresses p53-mediated anti-apoptotic response via induction of basic fibroblast growth factor

Although human telomerase catalytic subunit (TERT) has several cellular functions including telomere homeostasis, genomic stability, cell proliferation, and tumorigenesis, the molecular mechanism underlying anti-apoptosis regulated by TERT remains to be elucidated. Here, we show that ectopic expression of TERT in spontaneously immortalized human fetal fibroblast (HFFS) cells, which are a telomerase- and p53-positive, leads to increases of cell proliferation and transformation, as well as a resistance to DNA damage response and inactivation of p53 function. We found that TERT and a mutant TERT (no telomerase activity) induce expression of basic fibroblast growth factor (bFGF), and ectopic expression of bFGF also allows cells to be resistant to DNA-damaging response and to suppress activation of p53 function under DNA-damaging induction. Furthermore, loss of TERT or bFGF markedly increases a p53 activity and DNA-damage sensitivity in HFFS, HeLa and U87MG cells. Therefore, our findings indicate that a novel TERT-bFGF axis accelerates the inactivation of p53 and consequent increase of resistance to DNA-damage response.     

Importance of aliphatic C–H hydrogen bonding on anion recognition

We have designed and synthesised new anion receptors 1 and 2, both of their C–H groups were at the α positions to carbonyl groups and further polarised by the attached polarising substituents. This enabled us to study hydrogen bonding donor ability of C–H bonds. The polarising substituents are electron withdrawing cyano group for host 1, while charged pyridinium group for host 2. As expected from charge effects, host 2 shows roughly an order of magnitude higher binding constants against various anion guests than those of receptor 1. Since the magnitude of polarisation change should be greatest for C–H group among various hydrogen bonding groups, this indicates the importance of C–H hydrogen bonding. In contrast, the relative order of binding constants was the same for both host 1 and 2. The order of association constants was found to be (CH₃)₂POO^? > CH₃COO^? > C₆H₅COO^? > Cl^? > Br^?. DFT calculation results were in good agreement with experimental binding constants and confirmed the importance of charged group substitution. In addition, receptor 1 showed the highest association constant for dimethyl phosphinate, which is implicated in many metabolic diseases.     

Simultaneous determination of omeprazole and its metabolites in plasma and urine by reversed-phase high-performance liquid chromatography with an alkaline-resistant polymer-coated C18 column.

Omeprazole (OPZ) is a proton pump inhibitor in gastric parietal cells. A reversed-phase high-performance liquid chromatographic method was developed that enables concentrations of OPZ and its major metabolites, omeprazole sulphone (OPZ-SFN) and hydroxy-omeprazole (H-OPZ), to be determined simultaneously in plasma and that of H-OPZ in urine. To prevent decomposition of OPZ, all the processes (extraction, injection and elution) were carried out under alkaline conditions. Recoveries of the analytes and internal standard were greater than 93.1%. The intra- and inter-assay coefficients of variation were less than 9.1 and 6.4% for plasma samples and less than 2.9 and 3.9% for urine samples, respectively. The minimum determinable concentration (relative standard deviation 10-15%) was 10 ng/ml for all analytes in plasma and H-OPZ in urine samples. The clinical applicability of this assay method was evaluated by determining plasma concentration-and urinary excretion-time courses of the respective analyte(s) in four healthy volunteers after an oral dose of 20 mg of OPZ. The present assay is considered to be simple, precise and accurate and suitable for the study of the kinetic disposition and metabolism of OPZ, which is an extensively metabolized drug in the human liver.     

Plasma synthesis of nanosized W–Co composite powder followed by carburization with a methane–hydrogen mixture

Nanosized tungsten carbide and cobalt composite powder was synthesized by a two-step reaction via a thermal plasma process. Ammonium paratungstate (APT) and cobalt oxide were used as the precursors. The injected precursors were vaporized in the plasma flame and the subsequent reduction of the vaporized precursors produced uniformly mixed nanosized tungsten and cobalt composite powder. The subsequent carburization of this powder by CH₄–H₂ mixture resulted in the formation of nanosized WC–Co composite powder with a particle size <110 nm. This new method represents an alternative route that avoids the post-treatment required for the WC_1?x produced when methane was used for direct carburization in the powder production step.     

Isoperimetric numbers of graph bundles

The main aim of this paper is to give some upper and lower bounds for the isoperimetric numbers of graph coverings or graph bundles, with exact values in some special cases. In addition, we show that the isoperimetric number of any covering graph is not greater than that of the base graph. Mohar's theorem for the isoperimetric number of the cartesian product of a graph and a complete graph can be extended to a more general case: The isoperimetric numberi(G × K _2n) of the cartesian product of any graphG and a complete graphK _2n on even vertices is the minimum of the isoperimetric numberi(G) andn, and it is also a sharp lower bound of the isoperimetric numbers of all graph bundles over the graphG with fiberK _2n. Furthermore, ifn 2i(G) then the isoperimetric number of any graph bundle overG with fibreK _n is equal to the isoperimetric numberi(G) ofG. Partially supported by The Ministry of Education, Korea.     

Molecular lens of the nonresonant dipole force

A cylindrical molecular lens is formed by focusing a nanosecond IR laser pulse. Trajectories of a CS2 molecular beam deflected by the lens are traced using the velocity map imaging technique. The characteristic lens parameters including the focal length, minimum beam width, and distance to the minimum-width position are determined. The laser intensity dependence of the parameters is in good agreement with theoretical predictions. Exciting possibilities for molecular optics and a new type of optical chromatography are opened up.