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981.
Frogs are known to obtain some of their nutrients (e.g., glucose and sodium) through their skin. However, no studies have been made of the possible absorption of transition metals, which exist in most river water at low-ppb (w/w) levels. Therefore, this research was undertaken to evaluate the use of ion chromatography for such an investigation. Solutions of copper and zinc (20 ppb in each) were chosen for use in a small-scale screening study. Ten live frogs were each placed in individual baths for approximately 50 h. Of interest were the net changes in the concentrations of the metals. These differences were the result of any absorption and/or excretion processes that took place. A Dionex IonPac CS5 column was used to analyze this simulated river water, both before and after frogs had been placed in the solution. Included in this paper are: (1) methodology and calculation formulas; (2) precautions needed to ensure sample integrity; (3) statistical analyses, which indicated that ion chromatography is an accurate, precise technique for quantifying Cu and Zn in these samples; and (4) screening-study results, which were used to test the null hypothesis that frogs do not absorb copper and zinc either onto or through their skin. 相似文献
982.
Ponomarev N. E. Stambirskii M. V. Dvorko G. F. 《Russian Journal of General Chemistry》2002,72(1):79-85
The salt effect on the rate of dehydrobromination of 3-bromocyclohexene in PhNO2 depends on the nature of the verdazyl indicator. With triphenylverdazyl and its chloro and nitro derivatives in the presence of Et4NClO4, a normal salt effect is observed, in the presence of bromides, a superposition of normal and special salt effects, while in the presence of chlorides, a superposition of normal and special negative salt effects. With the dimethoxy verdazyl derivative, a normal salt effect is always observed. 相似文献
983.
An immobiline DryStrip application method enabling high-capacity two-dimensional gel electrophoresis 总被引:5,自引:0,他引:5
Sabounchi-Schütt F Aström J Olsson I Eklund A Grunewald J Bjellqvist B 《Electrophoresis》2000,21(17):3649-3656
In the field of proteomics the need to detect low-abundance cellular components, such as regulatory proteins, is of critical importance. Two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) is one of the most commonly used separation tools for these biological investigations. In this paper we report an alternative micropreparative 2-D PAGE sample application method, called the "paper bridge loading" method. This method makes it possible to apply a larger sample volume to commercially available immobilized pH gradient (IPG) strips. The Vh products required for focusing are only marginally longer than those used in analytical experiments. The method was compared to traditional cup loading and in-gel rehydration. With 18 cm long narrow-range Immobiline DryStrip pH 4.5-5.5, the "paper bridge" method allowed the application of 10 mg human plasma proteins compared to 3 mg with traditional loading methods. The corresponding figures using Escherichia coli sample was found to be 6 mg and less than 2 mg, respectively. The paper bridge method also showed the best results in terms of spot resolution and separation of high molecular weight proteins. 相似文献
984.
The analysis of 31P and 15N NMR data of a series of 40 iminophosphines R-P=N-R′ reveals that the E/Z-stereochemistry of the PN double bond can be predicted
on the basis of a simultaneous comparison of the values of δ31P and 1JPN.
Received: 31 May 1996/Revised: 2 July 1996/Accepted: 5 July 1996 相似文献
985.
986.
987.
988.
E. S. Domnina G. G. Skvortsova N. P. Glazkova M. F. Shostakovskii 《Chemistry of Heterocyclic Compounds》1967,2(3):283-286
The reaction of indole with acetylene under pressure is investigated. It is shown that under the action of KOH in aqueous dioxane at 220° C, N-vinylindole C10H9N is formed in 66% yield, and that this compound undergoes free radical and cationic polymerization. 相似文献
989.
990.
A technique for following the hydrolysis of pyromellitic acid dianhydride (PMDA) by differential thermal analysis (DTA) is described. On exposure of PMDA to moisture, an endothennic peak is initiated between 190 and 200 degrees . As the degree of hydrolysis increases, this peak becomes more intense and shifts to higher temperatures. The formation of pyromellitic acid (PMA) during the hydrolysis of PMDA can be determined qualitatively by DTA. 相似文献