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991.
A. A. Shachkus R. Yu. Dyagutite Z. A. Stumbryavichyute 《Chemistry of Heterocyclic Compounds》1990,26(5):527-529
Reaction of 2,3,3-trimethyl-and 2,3,3,5-tetramethyl-3H-indole hydrochlorides with methacrylic and crotonic amides gives 3- and 4-methyl-1,2,3,4,10,10a-hexahydropyrimido[1,2-a]indol-2-ones. With perchloric acid these are converted to 1-carbamoylpropyl-3H-indolium perchlorates. The syntheses of 10a-(4-dimethylaminostyryl)- and 10a-[(4-dimethylaminophenyl)butadienyl]-3,10,10-trimethylpyrimido[1,2-a]indol-2-ones have been studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 625–627, May, 1990. 相似文献
992.
Glatz Z Marini MV Wimmerová M Damborský J Nagata Y 《Journal of chromatography. A》2000,895(1-2):219-225
A new sensitive method has been developed for the determination of haloalkane dehalogenase activity. The enzymatic reactions were carried out directly in thermostatted autosampler vials and the formation of product - bromide or chloride ions - was monitored by sequential capillary zone electrophoresis runs. The determinations were performed in a 75 microm fused-silica capillary using 5 mM chromate, 0.5 mM tetradecyltrimethylammonium bromide (pH 8.4) as a background electrolyte, separation voltage 15 kV (negative polarity) and indirect detection at sample wavelength 315 nm, reference wavelength 375 nm for brominated and chlorinated substrates, respectively 0.1 M beta-alanine-HCl (pH 3.50) as a background electrolyte, separation voltage 18 kV (negative polarity) and direct detection at 200 nm for brominated substrates. The temperature of capillary was in both cases 25 degrees C. The method is rapid, can be automated, and requires only small amount of enzyme preparation and substrate. 相似文献
993.
A chromatographic method for the determination of transition metals in human hair samples is described. The method involves the separation of Cu, Pb, Zn, Ni, Co, Cd and Mn in a C18 column coated with sodium hexadecane-sulfonate (SHS) and spectrophotometric detection (520 nm) after post-column reaction of the eluted metals with 4-(2-pyridylazo)-resorcinol (PAR). The eluent was a 100 mM tartrate solution adjusted to pH 3.1 with a 2 M sodium hydroxide solution (flow-rate=1.0 ml min(-1)). A good separation of the eluted metals (specially for Cu/Pb and Zn/Ni) has been achieved. The detection limits, expressed as mug l(-1), were 2.2 (Cu), 8.0 (Pb), 2.8 (Zn), 1.5 (Ni), 1.5 (Co), 12.0 (Cd), and 1.4 (Mn). A microwave-assisted closed vessel acid digestion procedure with HNO(3)+HClO(4) (4+1 ml) was used for the hair samples solubilisation. Nineteen hair samples were analysed with the proposed method. The results were in good agreement with those obtained by atomic absorption spectrometry (AAS). 相似文献
994.
V. G. Berezkin E. G. Sumina S. N. Shtykov V. Z. Atayan D. A. Zagniboroda G. A. Nekhoroshev 《Chromatographia》2006,64(1-2):105-108
A new variant of thin-layer chromatography (TLC), based on a gradual change of mobile phase acidity during elution, is proposed.
The pH change occurs in the mobile phase moving along the TLC plate as a result of its contact with an acidic or a basic gas
phase that replaces the initial mobile phase vapor in the TLC chamber. The potential of this approach has been demonstrated
by using carbon dioxide and ammonia gases to improve the resolution of benzoic acids and aromatic amines on polyamide TLC
plates. 相似文献
995.
We have used the oscillating peroxidase-oxidase (PO) reaction as a model system to study how oscillatory dynamics may affect the influence of toxic reaction intermediates on enzyme stability. In the peroxidase-oxidase reaction reactive intermediates, such as hydrogen peroxide, superoxide, and hydroxyl radical are formed. Such intermediates inactivate many cellular macromolecules such as proteins and nucleic acids. These reaction intermediates also react with peroxidase itself to form an inactive enzyme. The fact that the PO reaction shows bistability between an oscillatory and a steady state gives us a unique possibility to compare such inactivation when the system is in one of these two states. We show that inactivation of peroxidase is slower when the system is in an oscillatory state, and using numerical simulations we provide evidence that oscillatory dynamics lower the average concentration of the reactive intermediates. 相似文献
996.
Y Masuo H Wang D Pélaprat Z Q Chi W Rostène 《Chemical & pharmaceutical bulletin》1992,40(9):2520-2524
We have recently demonstrated that [3H]ohmefentanyl, a non-peptidergic opioid ligand which was suggested to cross the blood brain barrier in contrast to other peptidergic opioid ligands, bound not only to mu opioid receptor sites but also to sigma sites. In order to examine whether [3H]ohmefentanyl can be used as a marker for mu sites, we investigated the effects of brain lesions on [3H]ohmefentanyl binding site densities, as compared with [3H][D-Ala2, MePhe4, Gly-ol5]enkephalin ([3H]DAGO), a selective mu ligand. These binding site densities were measured by quantitative autoradiography in the rat striatum and substantia nigra, two brain structures known to contain a high density of mu receptors, following lesions of the nigro-striatal dopaminergic pathway and striatal intrinsic neurons. Following unilateral nigral lesion with 6-hydroxydopamine, [3H]ohmefentanyl binding site densities were decreased in the patches (-35%) and matrix (-20%) of the ipsilateral striatum and in the lesioned substantia nigra pars compacta (-49%). Unilateral striatal lesion with quinolinic acid induced 72%, 61% and 50% decreases in [3H]ohmefentanyl binding in the patches and matrix of the lesioned striatum and in the ipsilateral substantia nigra pars reticulata, respectively. Similar results were obtained in the binding of [3H]DAGO. Indeed, a significant linear correlation was observed between [3H]ohmefentanyl and [3H]DAGO binding site densities. Therefore, mu opioid receptors may be mainly located on intrinsic neurons in the striatum, dopaminergic cell bodies in the substantia nigra pars compacta and nerve terminals of striatal efferents in the substantia nigra pars reticulata.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
997.
A quartz crystal microbalance has been proposed for studies on the temperature dependence of the linear rate of a reaction interface advance in topochemical reactions of the thermal decomposition of solids. A quartz crystal microbalance has been used in investigations of the CuSO4 · 5H2O dehydration. The data agree fairly well with those available in the literature. Advantages and disadvantages of the method proposed are discussed. 相似文献
998.
Gschwind RM Armbrüster M Zubrzycki IZ 《Journal of the American Chemical Society》2004,126(33):10228-10229
Hydrogen bonding plays a major role in the selective recognition of guanidinium groups by receptor molecules. The present NMR investigation provides direct experimental evidence of hydrogen bonds in an artificial arginine receptor complex consisting of alpha-N-benzoylarginine ethyl ester and a bisphosphonate tweezers molecule. trans-Hydrogen bond 2hJHP couplings between the phosphonate moieties and individual guanidinium protons as well as the amide proton have been detected by [1H,31P]-HMBC and [31P,1H]-INEPT experiments. The detected hydrogen bonding network in the investigated artificial arginine receptor shows a symmetrical end-on interaction of the guanidinium moiety, which enables concerted rotations and deviates from the structure proposed for the biological arginine fork. 相似文献
999.
A comprehensive study has been conducted to compare the adsorptions of alkali metals (including Li, Na, and K) on the basal plane of graphite by using molecular orbital theory calculations. All three metal atoms prefer to be adsorbed on the "middle hollow site" above a hexagonal aromatic ring. A novel phenomenon was observed, that is, Na, instead of Li or K, is the weakest among the three types of metal atoms in adsorption. The reason is that the SOMO (single occupied molecular orbital) of the Na atom is exactly at the middle point between the HOMO and the LUMO of the graphite layer in energy level. As a result, the SOMO of Na cannot form a stable interaction with either the HOMO or the LUMO of the graphite. On the other hand, the SOMO of Li and K can form a relatively stable interaction with either the HOMO or the LUMO of graphite. Why Li has a relatively stronger adsorption than K on graphite has also been interpreted on the basis of their molecular-orbital energy levels. 相似文献
1000.
Novel adsorbents which can concentrate Th(IV) in aqueous solution were prepared by immobilizingMyrica rubra tannin and larch tannin onto collagen fibre matrices. The adsorption capacities of the immobilized tannins to Th(IV) are
related to temperature and pH value of the adsorption process. For example, when the initial concentration of Th(IV) was 116.0
mg·l-1 and the immobilized tannin was 100 mg, the adsorption capacities of immobilized Myrica rubra tannin and larch tannin were 55.98 mg Th(IV)·g-1 and 13.19 mg Th(IV)·g-1, respectively at 303 K, and 73.67 mg Th(IV)·g-1 and 18.19 mg Th(IV)·g-1 at 323 K. It was also found that the higher adsorption capacity was obtained at higher pH value. The adsorption equilibrium
data of the immobilized tannins for Th(IV) can be well fitted by the Langmuir model and the mechanism of the adsorption was
found to be a chemical adsorption. In general, the adsorption capacity of immobilized Myrica rubra tannin to Th(IV) is significantly higher than that of immobilized larch tannin, probably due to the fact that the B ring
of Myrica rubra tannin has a pyrogallol structure which has higher reaction activity with metal ions. The breakthrough point of the adsorption
column of immobilized Myrica rubra tannin was at 33 bed volumes for the experimental system. The mass transfer coefficient of adsorption column determined by
Adams-Bohart equation was 1.61·10-4 l·mg-1.min-1. The adsorption column can be easily regenerated by 0.1 mol·l-1 HNO3 solution, showing outstanding ability of concentrating Th(IV).
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献