Separation and analysis of the soluble trimer of Aβ1-40 and its effects on the rise in intracellular calcium

Alzheimer’s disease (AD) is one of the progressive neurodegenerative diseases associated with protein conformational transition, generally known as protein conformational disorders[1]. The general characteriza- tions of AD are the intracellular fibrillar…     

SEC储量评估参数取值方法及应用

本文从SEC储量定义及评估准则入手,结合国内上市储量评估的实践,阐述了新增探明、已开发、未开发三类上市储量,按照SEC准则确定评估参数(开发参数、经济参数)和现金流法计算剩余经济可采储量的方法,并以实例进行了说明。最后指出了SEC储量评估中应注意的几个问题,以期对国内上市储量评估有所借鉴。     

Composition, structure and solution properties of polysaccharides extracted from leaves of Mesembryanthenum crystallinum

Water and Chelator-soluble polymers were independently isolated from the alcoholic-insoluble substance (AIS) of Mesembryanthenum crystallinum leaves. After precipitation in ethanol and ultrafiltration (40 kD cut-off) of recovered solids dissolved in water, the yield relative of the so-call Lw and LCh polymers to the AIS dry matter was 2.5 ± 0.2 and 7 ± 0.5%. The galacturonic acid contents were 67 ± 3% and 63 ± 5%. The degrees of methylesterification of ca. 45 ± 3% and 50 ± 3%, showed that Lw and LCh belonged to the fairly methylesterified pectin class. From sugar analysis, LCh was shown to contain at least two types of pectic blocks, homogalacturonan (HG: 58%) and rhamnogalacturonan-I (RG-I: 34%). Their structure were deduced after saponification, polygalacturonase treatments, size exclusion chromatography (SEC) onto Sephacryl S-200 and then sugar composition of the collected fractions. The main polymers were methylesterified HG (32%), some of them being linked to non-methylesterified HG (10%), and to polygalacturonase-resistant HG (17%). In addition, there were (1) a highly soluble RG-I with long galactan side chains (RG-I-gal accounting for 9%) and (2) a RG-I with short arabino-galactan side chains (25%), named RG-I-ara/gal that was almost totally lost during SEC analysis, due to its low solubility at room temperature and in absence of chelators.SEC coupled with differential refractive index and light scattering showed that highly methylesterified HG chains exhibited aggregate structures in solution due to intermolecular hydrophobic interactions. These interactions formed hydrophobic clusters, which have been characterized by surface tension measurements and with a polarity probe, the Coomassie Brilliant Blue dye. After alkaline treatment of LCh, the self-assembly of HG disappeared.     

Dilute solution properties of epoxy resins

Number-average molecular weights of fractions of epoxy resins were estimated by vapor-pressure osmometry and size exclusion chromatography coupled with multiple-angle light scattering. Potential reasons for differences between the two sets of data are examined. The molecular weight dependences of the intrinsic viscosity in tetrahydrofuran and chloroform are discussed in terms of theories which take into account the low-molecular weight character of poly(hydroxy ether) chains. The polymer-solvent interaction parameter is estimated. The impact of the presence of branched chains on the results of size exclusion chromatography is examined. It is shown that the universal calibration of size exclusion chromatographic columns by polystyrene is reliable at molecular weights above 2000 only.     

1H NMR Analysis of Long-Chain-Branched Strong Polyelectrolytes Obtained by Vinyl/Divinyl Monomer Copolymerization in Aqueous Medium

Statistical long-chain branching occurring during the free-radical polymerization of the system sodium 4-vinylbenzenesulfonate (SSNa) and N, N′-methylene-bis(acrylamide) (MBAA) in aqueous medium was studied by ¹H NMR spectroscopy and SEC. The former method yielded the degree of conversion and the content of the three monomer units in the chain, i.e., SSNa, MBAA with pendant vinyl groups, and MBAA as branching points. It was found that the number of individual monomer units per a total of 1000 monomer units does not perceivably change with the degree of conversion and only slightly increases with increasing ratio MBAA/SSNa in the feed.     

Reversed-phase high-performance liquid chromatographic, size exclusion chromatographic and polyacrylamide gel electrophoretic studies of glycinin: evidence for molecular species and their association-dissociation

Isolation and purification of glycinin and its molecular species from an Indian soybean variety (JS-335) was achieved using polyacrylamide gel electrophoresis (PAGE), size exclusion chromatography (SEC) and reversed-phase high-performance liquid chromatography (RP-HPLC). Glycinin was found to have two molecular species (glycinin I and II), and only glycinin I underwent reversible dissociation-association system into alpha and beta species. Glycinin I and II were not found to constitute a dissociation-association system. Glycinin II also did not dissociate under varying conditions of time, pH and ionic strength of buffer. Various species so dissociated were isolated, purified and characterized.     

Characterization of N-vinyl carbazole/vinyl 4-tert-butyl-benzoate copolymers of several molar compositions: SEC, DSC and intramolecular excimers in dilute solutions

Several N-vinylcarbazole/vinyl p-tert-butyl-benzoate copolymers of different molar monomer compositions and their respective homopolymers have been synthesized by free-radical polymerization. Their solution properties were characterized by size-exclusion chromatography (SEC) coupled with a differential refractive index (RI) and multiangle light scattering (MALS). Differential scanning calorimetry (DSC) was also used to investigate the glass transition temperatures, T_g. In addition, steady-state fluorescence emission spectra in a dilute solution of several fluid and non-fluid solvents were obtained to study the influence of monomer composition on the intramolecular carbazole excimer formation. The amount of excimers strongly depends on the solvent nature and copolymer composition. Molecular Dynamics (MD) simulations on iso- and syndiotactic homopolymer and copolymer fragments were used to obtain the probability of the conformations that satisfy excimer requirements. The analysis of the MD trajectories allows us to evaluate the amount and types of intramolecular excimers for the different systems.     

用于现场FTIR及UV/Vis光谱电化学的高质量简单结构的光透薄层电化学池

设计制作了一种应用于紫外可见、红外电谱电化学的新型光透薄层电化学池(OTTLE),并以铁氰化钾水溶液、二茂铁乙腈溶液体系进行了表征。池腔几何结构的合理设计使电位降和边缘效应降至最低。该池有良好的伏安响应特性并可用它得到高质量的UV/Vis和IR光谱。由于简单的结构及低廉的造价使适用于光谱电化学研究的电化学池变得更容易得到。     

Bioaccumulation of metals and induction of metallo‐ thioneins in selected tissues of common carp (Cyprinus carpio L.) co‐exposed to cadmium,mercury and lead

The concentrations of mercury (Hg), cadmium (Cd) and lead (Pb) at various exposure periods were determined in the gill, kidney, liver and muscle of common carp (Cyprinus carpio L.) co‐exposed to 1.0 µg ml^?1 each of Cd²⁺, Hg²⁺ and Pb²⁺ for up to 10 days. Metallothionein fractions (MTs) in these organs were characterized using the hyphenated technique of size‐exclusion chromatography (SEC) and inductively coupled plasma mass spectrometry (ICP‐MS). After 10 days of exposure, maximum toxic metal concentrations of Hg, Cd and Pb were 10.7 (gill), 0.145 (kidney) and 0.112 µg g^?1_dryweight (gill), respectively. The pattern of accumulation of Hg and Pb was in the order gill > kidney > liver > muscle. In the case of Cd, accumulation was in the order kidney > gill > liver > muscle. Cd and Hg binding MTs were significantly induced in the gill, kidney and liver of all the exposure groups in comparison with the control group (p < 0.05), and the amounts of them increased with the longer exposure time. Despite the higher intracellular Hg concentration and the stronger Hg? SH binding affinity, the amount of Cd‐binding MTs was much higher than that of Hg‐binding MTs. The results indicate that MT synthesis in these organs was clearly metal‐specific. MTs in gill may be used as a bio‐marker to detect the metal pollution caused by Hg and Cd. Zinc and copper binding MTs in the organs of the exposed fish were also increased. This may be due to the MTs' important role in the homeostatic regulation of essential metals and their protective role against the acute toxicity of non‐essential metals. Even though there was considerable accumulation of lead in the organs of the exposed fish, Pb‐binding MT synthesis was non‐significant. Copyright © 2006 John Wiley & Sons, Ltd.