Isotachophoretic analysis of the dihydrofolate reductase reaction in the presence of methotrexate and ascorbic acid

The antifolate methotrexate (MTX) is widely used in cancer chemotherapy. In this study, we show that MTX (MTX-Glu1) and MTX-polyglutamates (MTX-Glu2-5) strongly inhibited the growth of the leukemic cell line MOLT-4. This effect, however, was mitigated by ascorbic acid. We investigated whether ascorbic acid is able to reduce dihydrofolic acid (DHF) to tetrahydrofolic acid (THF) directly or by circumventing the MTX inhibition of dihydrofolate reductase (DHFR). The inhibition of this NADPH-dependent reduction of DHF by MTX-Glun in the absence or presence of ascorbate, was determined by analytical isotachophoresis. Using 0.01 M HCl/histidine, pH 6.0, as a leading electrolyte (L) and 0.005 M 2-(N-morpholino)ethanesulfonic acid (MES)/histidine, pH 6.0, as a terminating electrolyte (T), MTX-Glun derivatives including MTX-Glu1 could be easily separated, whereas the quantitative estimation of THF was not possible. A quantitative characterization of the DHFR reaction by measuring NADPH, NADP+ and ascorbate was achieved with another system (L: 0.01 M HCI/beta-alanine, pH 3.73; T: 0.01 M caproic acid, pH 3.27). Nanomolar concentrations of MTX-Glu1-5 inhibited consumption of NADPH and production of NADP+. Ascorbic acid was not able to reduce DHF, neither directly nor after inhibition of DHFR by MTX. However, ascorbic acid seemed to diminish the oxidation of THF and this may account for its capacity to reduce the inhibitory effect of MTX on MOLT-4 cells.     

The Synthesis of Novel Crown Ethers, Part VII [1]. Coumarin Derivatives of Benzocrowns and Cation Binding from Fluorescence Spectra

4-[3-(1-benzopyran-2-one)] derivativesof benzo[12]crown-4, benzo[15]crown-5 andbenzo-[18]crown-6 were synthesized from4-[3-(1-benzopyran-2-one)]-1,2-dihydroxy-benzenereacting with bis-ethyleneglycol dihalides orpentaethylene glycol ditosylate in alkali carbonate/DMF/water. The original products were identified byhigh resolution EI-mass spectra as well as IR,¹H-NMR and ¹³C-NMR spectroscopy. The 1 : 1binding constants of Mg²⁺, Li⁺, Na⁺ andK⁺ with the coumarin-benzocrowns were estimated usingfluorescence emission spectroscopy in acetonitrile.The complexing enhanced quenching fluorescence spectra(CEQFS) and complexing enhanced fluorescence spectra(CEFS) exhibited the ion binding powers due tocationic recognition rules of the macrocycles.     

Modelisation Des Nappes De Solubilite Du Diagramme De Phases Mg(NO3)2–Al(NO3)3–H2O

A program has been written to describe solubility surfaces of the polythermal ternary phase diagram Mg(NO₃)₂–Al(NO₃)₃–H₂O, using the model proposed by Cohen-Adad et al. [2]. In this work we present the calculation of the solubility surface of Mg(NO₃)₂×6H₂O and Al(NO₃)₃×9H₂O in the phase diagram. The calculated isothermal sections are in a good agreement with experimental determinations. Coefficients of the fitting equation that describes the solubility field allow drawing any isothermal section. The monovariant line was also calculated. The chosen model is well adapted to calculations of these solubility surfaces and gives very good results. This revised version was published online in August 2006 with corrections to the Cover Date.     

Septorine and N-methoxy septorine,substituted pyrazines from the fungus Septoria nodorum berk

On the basis of ¹H nmr correlations with synthetic analogs, structures $\text{1}$ and $\text{2}$ are proposed for septorine and N-methoxy septorine, two p-hydroxybenzoyl 1-isobutyl substituted pyrazines obtained from the fungus $\text{Septoria nodorum}$ Berk, a parasite of wheat.     

Mise en evidence de la formation de R2MMR2 a partir de disila-1,2 et digerma-1,2 cyclohexenes-4

Intermediates with π-bonded Si or Ge are generated during gas phase pyrolysis of 1,2-disila- or 1,2-digerma-cyclohex-4-enes.Compounds such as R₂MMR₂ are successfully trapped by addition or [2 + 2] and [4 + 2] cycloadditions. These results were proved by mass spectrometry.     

灵芝及虫草菌丝体中微量元素含量的分析

利用原子吸收光谱法和分光光度法对人工培育的灵芝,灵芝孢子粉,虫草菌丝体中具有重要生理意义的元素锌,铁,锰,镁,锗进行了检测,比较了灵芝子实体,灵芝孢子粉,虫草菌丝体中５种元素的含量,探讨了５种元素的药理作用。     

微波炉溶样-原子吸收光谱法测定油漆中铅含量

采用密封罐密封,微波炉加热消化,原子吸收分光光度法测定了油漆中的铅含量。本文简单快速、无污染。回眉率９８．７％－１０４％     

锌与疾病关系的探讨

综述了锌与健康的关系,包括：锌的代谢,锌的主要功能,锌与疾病治疗等方面,参考文献16篇。     

中药黄芩及其混伪品的模糊聚类分析

采用模糊聚类分析法对黄芩及其混伪品进行了聚类分析,为中药材的质量鉴定提供了新方法。     

Volume and heat capacity of model non-aqueous self-assembly systems

Blends of immiscible polymers are often stabilized by block copolymers which can form non-aqueous micelles and microemulsions in the liquid polymers. The phase diagrans, apparent volumes and apparent heat capacities of model non-aqueous binary and ternary systems were studied in order to investigate the conditions under which such self-assembly systems could form. 1,2-Hexanediol, which can cosolubilize hexane and ethyleneglycol, forms inverse micelles in hexane and weak microaggregates in ethyleneglycol. Genapol X-060, a commercial alcoholic surfactant containing on the average an aliphatic chain of 13 carbons and 6 oxyethylenes (C₁₃E₆), forms microaggregates in poly(ethyleneglycol) 400. These self-assembly systems are strengthen in the presence of a third component which has an affinity for the inner phase.Presented at the Symposium, 76^th CSC Congress, Sherbrooke, Quebec, May 30–June 3, 1993, honoring Professor Donald Patterson on the occasion of his 65^th birthday.