微乳液介质—1—（2—吡啶偶氮）—2—萘酚光度法测定汽油中环烷酸铁的含量

本研究了微乳液为介质时，铁与１－（２－吡啶偶氮）－２－萘酚（ＰＡＮ）的显色反应。选择７３０ｎｍ处为测定波长，ε为１．４×１０＾４Ｌ．ｍｏｌ＾－＾１．ｃｍ＾－＾１，铁量在０－５０μｇ／２５ｍｌ范围内符合比耳定律，该法适用于汽油中环烷酸铁的测定。     

铜、钴、镍同时分离工艺的研究

稀土体系三种元素同时分离的工艺最近已有发表,但非稀土方面的工作尚未见报导.对Cu、Co、Ni三种元素,通常是将Cu、Co作为一个组份与Ni分离.本工作对组成为Cu:Co:Ni=1:1:1的水相合成料液设计了两种工艺,进行了串级实验,实现了该三种元素的同时分离, 串级实验以HEH(EHP)作萃取剂,煤油为稀释剂,其它试剂均用分析纯.     

基团的电子效应与单取代苯对位^1H,^13C的化学位移

基团的电子效应与单取代苯对位１Ｈ、１３Ｃ的化学位移＊韩长日冯娇杨钟照平（海南师范学院化学系海口５７１１５８）关键词１Ｈ的化学位移１３Ｃ的化学位移基团电负性共轭效应引言在１Ｈ、１３Ｃ核磁共振谱中，化学位移值的大小主要取决于屏蔽作用的大小，而屏蔽作用的大...     

Speciation of dissolved iron(II) and iron(III) in environmental water samples by gallic acid-modified nanometer-sized alumina micro-column separation and ICP-MS determination

A method has been developed for the speciation of trace dissolved Fe(II) and Fe(III) in water by coupling gallic acid (GA) modified nanometer-sized alumina micro-column separation with inductively coupled plasma mass spectrometry (ICP-MS). The separation of Fe(II) and Fe(III) was achieved based on the obvious difference in reaction kinetics between Fe(II) and Fe(III) with GA. Fe(III) was selectively retained on the micro-column at pH 5.5-6.5, while Fe(II) could not be retained by the micro-column at the whole tested pH range of 1.0-6.5, and passed through the micro-column. The Fe(II) can be determined by ICP-MS directly without preconcentration/separation procedure, while Fe(III) retained on the micro-column was then eluted with 1.0 mL of 1 mol L(-1) HCl and determined by ICP-MS. The parameters affecting the separation of Fe(II) and Fe(III) were investigated systematically and the optimum separation conditions were established. Under the optimized conditions, the detection limits of 0.48 microg L(-1) and 0.24 microg L(-1) with relative standard deviation of 5.6% and 4.3%(C= 5 microg L(-1), n= 7) for Fe(II) and Fe(III) were found, respectively. No obvious effect on the speciation of Fe(II) and Fe(III) was found with the change of the ratio of Fe(II) and Fe(III) from 0 ratio 10 to 10 ratio 0. The proposed method was applied for the determination of trace Fe(II) and Fe(III) in environmental water and the recoveries for spiked samples were found to be in the range of 97-105%.     

Loniceroside C,an antiinflammatory saponin from Lonicera japonica

A new triterpenoid saponin, loniceroside C was isolated from the aerial parts of Lonicera japonica. Its structure was established to be 3-O-beta-D-glucopyranosyl hederagenin 28-O-alpha-L-rhamnopyranosyl (1-->2)-[beta-D-xylopyranosyl(1-->6)]-beta-D-glucopyranosyl ester by spectroscopic techniques and chemical transformations. Loniceroside C showed in vivo antiinflammatory activity against mouse ear edema provoked by croton oil.     

Synthesis and Kinetic Study on the Chromium(III) Complex [Cr(ASA)(en)2]Cl·2H2O

In order to explore the transfer mechanism of chromium(III) in mammals, a novel complex [Cr(ASA)(en)₂]Cl· 2H₂O, bis(ethylenediamine‐ κ ² N,N′)(4‐aminosalicylic acid‐ κ ² O,O′) chromium(III) monochloride dihydrate was synthesized (4‐aminosalicylic acid=H₂ASA, ethylenediamine=en). The crystal structure belongs to orthorhombic system with the space group P2₁2₁2₁ by means of X‐ray diffraction. The characteristic for transfer of Cr³⁺ from the compound to the low‐molecular‐mass chelator EDTA and the iron‐binding protein apoovotransferrin (apoOTf) was followed by UV‐visible (UV‐Vis) and fluorescence spectra in 0.01 mol·L^?1 Hepes at pH 7.4. The second order rate constants were calculated. Those spectra in conjunction were used to obtain more accurate information about the interaction of chromium complex with apoOTf. The experimental results indicate that Cr³⁺ can be transferred from the complex to apoOTf with the retention of the 4‐aminosalicylic acid acting as a synergistic anion.     

Effect of the Secondary Reduction on the Enantioselectivity and Function of Additives in the Chiral Oxazaborolidine‐Catalyzed Asymmetric Borane Reduction of Ketones

The secondary reduction in the direct and oxazaborolidine‐catalyzed asymmetric borane reduction of ketones was investigated by the use of GC/MS tracing titration and control experiments. The results indicate that the secondary reduction affects the enantioselectivity only in noncoordinated solvents at low temperature and not under the usual catalytic reduction conditions because the intermediate alkoxyborane is unstable and quickly converts to borane and dialkoxyborane. The function of an alcohol additive in the asymmetric borane reduction of ketones is to consume excess borane in the reduction system thus inhibiting noncatalytic reduction, which leads to increased enantioselectivity in the catalytic reduction.     

CHIP-mediated hyperubiquitylation of tau promotes its self-assembly into the insoluble tau filaments

The tau protein is a highly soluble and natively unfolded protein. Under pathological conditions, tau undergoes multiple post-translational modifications (PTMs) and conformational changes to form insoluble filaments, which are the proteinaceous signatures of tauopathies. To dissect the crosstalk among tau PTMs during the aggregation process, we phosphorylated and ubiquitylated recombinant tau in vitro using GSK3β and CHIP, respectively. The resulting phospho–ub-tau contained conventional polyubiquitin chains with lysine 48 linkages, sufficient for proteasomal degradation, whereas unphosphorylated ub-tau species retained only one–three ubiquitin moieties. Mass-spectrometric analysis of in vitro reconstituted phospho–ub-tau revealed seven additional ubiquitylation sites, some of which are known to stabilize tau protofilament stacking in the human brain with tauopathy. When the ubiquitylation reaction was prolonged, phospho–ub-tau transformed into insoluble hyperubiquitylated tau species featuring fibrillar morphology and in vitro seeding activity. We developed a small-molecule inhibitor of CHIP through biophysical screening; this effectively suppressed tau ubiquitylation in vitro and delayed its aggregation in cultured cells including primary cultured neurons. Our biochemical findings point to a “multiple-hit model,” where sequential events of tau phosphorylation and hyperubiquitylation function as a key driver of the fibrillization process, thus indicating that targeting tau ubiquitylation may be an effective strategy to alleviate the course of tauopathies.

Multiple-hit model for tau aggregation, where sequential events of tau phosphorylation and hyperubiquitylation function as a key driver of the fibrillization process.     

Enthalpy of Adsorption and Isotherms for Adsorption of Naphthenic Acid onto Clays

The enthalpies of adsorption and the isotherms for adsorption of naphthenic acid onto Na-montmorillonite, Na-kaolinite, and Na-illite were studied by means of calorimetry and the static method at 298.15 K. The results show that the enthalpies of adsorption and saturated adsorption amounts of naphthenic acid on different clays change in the order Na-montmorillonite > Na-illite > Na-kaolinite. The interaction between naphthenic acid and clays is discussed.     

Large-volume stacking in capillary electrophoresis using pH hysteresis of the electroosmotic flow in a bare fused-silica capillary

For large-volume stacking with the electroosmotic flow pump (LVSEP) in capillary electrophoresis of anionic analytes it is required that the electroosmotic mobility (EOM) should be smaller than the magnitudes of the effective mobilities of the analytes. When a fused-silica capillary is treated with an acidic solution, the silanoate group on the silica surface is neutralized to silanol and the EOM is suppressed. Due to the slow deprotonation equilibrium of the silanol group at an intermediate pH, this reduced EOM can be retained during a number of electrophoresis runs. Using a bare fused-silica capillary preconditioned with 0.01 M HCl, successful LVSEP at pH 6.0 was achieved for weakly acidic compounds with two orders of magnitude enhancements in the concentration sensitivity. The repeatability in migration times of ten analytes stacked by LVSEP in a single day was excellent with the relative standard deviation (RSD) less than 1% (n = 6). The day-to-day repeatability was also excellent with RSD less than 3% (n = 3 x 6) when the capillary was preconditioned each day.