Computer simulation of Gd(III) speciation in human interstitial fluid

The speciation and distribution of Gd(III) in human interstitial fluid was studied by computer simulation. Meantime artificial neural network was applied to the estimation of log beta values of complexes. The results show that the precipitate species, GdPO4 and Gd-2(CO3)(3), are the predominant species. Among soluble species, the free Gd(III), [Gd(HSA)], [Gd(Ox)] and then the ternary complexes of Gd(III) with citrate arc main species and [Gd-3(OH)(4)] becomes the predominant species at the Gd(III) total concentration or 2.2x10(-2)mol/L.

Solvent extraction of scandium(III) by Cyanex 923 and Cyanex 925

The extraction equilibria of Sc(III), Zr(IV), Ti(IV), Th(IV), Fe(III) and Lu(III) from sulphuric or hydrochloric acid media by Cyanex 923 (mixture of straight chain alkylated phosphine oxides) and Cyanex 925 (mixture of branched chain alkylated phosphine oxides) were studied at various aqueous acidities. The extractant Cyanex 923 demonstrated better scandium loading and selectivity for TI(IV). Fe(III) and Lu(III) than Cyanex 925. The effects of extractant concentration on the extractions of sulphuric acid and Sc(III) by Cyanex 923 were examined. The stoichiometries of the extraction reactions were postulated based on slope analysis. The experimental results indicate that Cyanex 923 can be employed to recover scandium directly from the hydrolytic mother solution arising from TiO2 production via the sulphate process. The parameters studied were scandium loading capacity, phase ratio, concentrations of Ti(IV) scrubbing and Sc(III) stripping agents. A new solvent extraction technology of scandium recovery was developed. The purity of the final Sc(III) product is above 95% with a yield > 94%. (C) 1998 Elsevier Science B.V.

圆斑蝰蛇毒磷脂酶A_2蛋白活性表现和分子进化探讨及菜花烙铁头、烙铁头蛇毒中Jerdonase、TmF的研究

磷脂酶AZ（PLA2）是蛇毒中含量较为丰富的一类作用于梭酷键的酶。迄今为止，己有多种形式的PLA2从不同地域、不同种属的蛇毒中得以纯化并进行了较为系统的研究。其中，以VipoXin为代表的异二聚体形式PLA2较为引人注目，原因在于这种形式不同于此类蛋白家族中的诸多其它个体。目前，己经有许多关于此异二聚体PL凡生物学特性的报道，包括对此类形式存在原因、活性变化、结构表现、系统进化等方面的讨论。然而至今，这种以异二聚体形式存在的PLA2仅发现于几种蛙亚科（ViperinaeSubfamily）蛇种的蛇毒中，其中就包括我国台湾岛的圆斑蜂蛇台湾亚种（Doboiarusselliiformosensis），而蝮亚科（CrotaiinaeSubfamil）蛇种的蛇毒至今却没有此类报道。我国大陆西南端接壤东南亚，存在于云南、福建一带的圆斑蛙蛇隶属圆斑蛙蛇泰国亚种（Daboiarusselliisiamensis），那么这种蛇毒中是否也含有异二聚体形式的PLA2呢？本工作就此疑问对云南产圆斑蛙蛇泰国亚种（D.r.siamensis）蛇毒中的PLA2进行了研究，结果得到三个新的PLAZ，分别命名为DRS-PLA2-I、DRS-PLA2-II和DRS-PLA2-III。其中，DRS-PLA2-I的分子量为13864.06Da，理论pI为4.56，PLA2活性为12.35μmol/mg/min；DRS-PLA2-II的分子量为13635.99Da，理论pI为8.74，PLA2活性为8.76μmol／mg/min；DRS-PLA2-III的分子量为13619.80Da，理论厂为4.61，无PLA2活性。这三个蛋白酶N端的30个氨基酸残基恰好和三个阳性克隆的cDNA序列推导的蛋白序列吻合，结合已经报道的PLA2蛋白家族蛋白序列的保守性表现，我们可以断定它们之间存在对应关系。分子系统学分析表明DRS-PLA2-II和DRS-PLA2-III在进化关系上和蛙亚科的异二聚体PLA2关系较近，并且二者酶活性分别与异二聚体PLA2的Normalchain和Inhibitorchain相一致，只是没有发现类似Vipoxin形式的异二聚体结合蛋白。这些分析表明DRS-PLA2-nORS-PLA2-III类似圆斑蛙蛇台湾亚种（D.r.forlnos翻s沽）中的PV-4/RV-7，是PLA2异二聚体的一种特殊形式，在进化上滞后于VinOXin。另夕卜本工作还相继从云南产菜花烙铁头（Trimeresrusjerdonii）蛇毒和湖南产烙铁头（Trimeresurusmucrosquamatus）蛇毒中分离得到Jerdonase和TmF。前者为一个丝氨酸蛋白酶性质的、具有纤维蛋白原水解作用和激肤释放酶原水解作用双重活性表现的、高分子量的份五brinogenase，其活性表现可以被PMSF彻底抑制，而EDTA对此却没有影响。其它的几种抑制剂如大豆胰蛋白酶抑制剂、l-cysteine、DTT对Jerdonase的活性表现也有不同程度的影响。在Jerdonase的这些生化特性上中，分子量的大小和对纤维蛋白酶水解的特性这两方面有别于蛇毒中诸多其它来源的同类蛋白；后者T淤为一个舒缓激肚增强肤（BradykninPQtentiatingPePtide，BPP），电离质谱分析表明其分子量为1110.7Da。此小肚氨基酸序列为促进舒缓激肚（Bradki垃n，BK）诱导的豚鼠回肠纵行肌收缩的活力单位为（1.13±0.3）（m留L），T妊抑制血管紧张素转化酶（ACE）对BK水解的半数抑制剂量IC50为2μg。比较已报道的从Agkistrodon属和Bothrops属中纯化得到的BPP氨基酸序列发现：BPP的N端都是特征性的pGlu，C端为IIe-Pro-Pro，有高度的保守性。另外，TmF是Trimeresurus属中此类小肤的首次纯化。总之，本研究对国产的几种常见蛇毒中的几种常见蛋白多肤进行了一定程度的探讨和分析，和相同类别的其它蛋白、多肤比较可以看到，有许多相同的地方，也有许多不同的表现，研究结果为相应领域的深入研究提供资料和思路。

Ethylene polymerization, and the copolymerizations of ethylene with hexene or norbornene with highly active mono(beta-enaminoketonato) vanadium(III) catalysts

Five novel vanadium(III) complexes [PhN = C(R-2)CHC(R-1)O]VCl2(THF)(2) (4a: R-1 = Ph, R-2 = CF3; 4b: R-1 =t-Bu, R-2 = CF3; 4c: R-1 = CF3, R-2 = CH3; 4d: R-1 = Ph, R-2 = CH3; 4e: R-1 = Ph, R-2 = H) have been synthesized and characterized. On activation with Et2AlCl, all the complexes, in the presence of ethyl trichloroacetate (ETA) as a promoter, are highly active precatalysts for ethylene polymerization, and produce high molecular weight and linear polymers. Catalyst activities more than 16.8 kg PE/mmolv h bar and weight-average molecular weights higher than 173 kg/ mol were observed under mild conditions.

The asymptotic near-tip solution for mode-iii crack in steady growth in power hardening media

Two local solutions, one perpendicular and one parallel to the direction of solar gravitational field, are discussed. The influence of gravity on the gas-dynamical process driven by the piston is discussed in terms of characteristic theory, and the flow field is given quantitatively. For a typical piston trajectory similar to the one for an eruptive prominence, the velocity of the shock front which locates ahead the transient front is nearly constant or slightly accelerated, and the width of the compressed flow region may be kept nearly constant or increased linearly, depending on the velocity distribution of the piston. Based on these results, the major features of the transient may be explained. Some of the fine structure of the transient is also shown, which may be compared in detail with observations.

A novel short neurotoxin, cobrotoxin c, from monocellate cobra (Naja kaouthia) venom: isolation and purification, primary and secondary structure determination, and tertiary structure modeling

A novel short neurotoxin, cobrotoxin c (CBT C) was isolated from the venom of monocellate cobra (Naja kaouthia) using a combination of ion-exchange chromatography and FPLC. Its primary structure was determined by Edman degradation. CBT C is composed of 61 amino acid residues. It differs from cobrotoxin b (CBT B) by only two amino acid substitutions, Thr/Ala11 and Arg/Thr56, which are not located on the functionally important regions by sequence similarity. However, the LD50 is 0.08 mg/g to mice, i.e. approximately five-fold higher than for CBT B. Strikingly, a structure-function relationship analysis suggests the existence of a functionally important domain on the outside of Loop III of CBT C. The functionally important basic residues on the outside of Loop III might have a pairwise interaction with alpha subunit, instead of gamma or delta subunits of the nicotinic acetylcholine receptor (nAChR). (C) 2002 Elsevier Science Inc. All rights reserved.

Genetic diversity of plankton community as depicted by PCR-DGGE fingerprinting and its relation to morphological composition and environmental factors in lake donghu

To collect information about the genetic diversity of the plankton community and to study how plankton respond to environmental conditions, plankton samples were collected from five stations representing different trophic levels in a shallow, eutrophic lake (Lake Donghu), and investigated by PCR-DGGE fingerprinting. A total of 100 bands (61 of 16S rDNA bands and 39 of 18S rDNA bands) were detected. The DGGE bands unique to any single station accounted for 38% of the total bands, whereas common bands detected at all five stations accounted for only 11%. Using UPGMA clustering and MDS ordination of DGGE fingerprints, stations I and II were found to initially group together into one cluster, which was later joined by station V. Stations III and IV were isolated into two separate groups of one station each. Some differences in grouping relationships were found when analysis was completed on the basis of chemical characteristics and morphological composition, with zooplankton composition showing the greatest variability. However, the most similar stations (I and II) were always initially grouped into one cluster. Moreover, stations that exhibited the same or similar trophic level (stations III and IV), but different concentrations of heavy metals, were further differentiated by the DGGE method. Results of the present study indicated that PCR-DGGE fingerprinting was more sensitive than the traditional methods, as other studies suggested. Additionally, PCR-DGGE appears to be more appropriate for diversity characterization of the plankton community, as it is more canonical, systematic, and effective. Most importantly, fingerprinting results are more convenient for the comparative analyses between different studies. Therefore, the use of the described fingerprinting analysis may provide an operable and sensitive biomonitoring approach to identify critical, and potentially negative, stress within an aquatic ecosystem.

Simultaneous determination of chromium(VI) and chromium(III) of bioavailable fraction in bottom mud by flow injection-atomic absorption spectroscopy

A rapid and sensitive method for separation and determination of Cr(VI) and Cr(III) in bottom mud of lake by flow injection on-line preconcentrtion system and GFAAS was developed. The available Cr(VI) and Cr(III) were extracted by HOAc or EDTA + NH4 NO3 and adsorbed simultaneously by an anion and a cation resin microclummn and then eluted simultaneously by 2 mol/L NH4 NO3 + 0.05 mol/L ascorbate and 2 mol/L H2SO4, respectively. The elution was performed for 50 s after adsorption for 2 min, and the efficiencies of elution were 85.4% - 94.8% and 96.7% - 106% for Cr(VI) and Cr(M) respectively. The detection limits of the method were 0.9 mu g/L and 2.7 mu g/L with relative standard deviations of 3.5% and 6.4% for the determination of Cr(VI) and Cr(III) in sample, respectively.

Study on fluorescence emission and synchronous-scan fluorescence spectrea of Nitzschia hantzschiana solution with FE(III)

The characterization of the algal Nitzschia hantzschiana solution with (or without) Fe(III) was carried out using fluorescence emission and synchronous-scan spectroscopy. An emission peak (excited at 440 nm) was observed at 675 nm for Nitzschia hantzschiana solution. The effective characterization method used was synchronous-scan fluorescence spectroscopy (SFS). A wavelength difference (Delta lambda) of 90 nm was maintained between excitation and emission wavelengths. The peak was observed at about 236(ex) nm (326(em) nm) for synchronous fluorescence spectroscopy. Fe(III) was an effective quencher. The relationship between I-0/I (quenching efficiency) and c (concentration of Fe (III) added) was a linear correlation for the algal solution with Fe(III). Effects of pH on synchronous-scan fluorescence intensity were evident.

Preliminary study on the photoproduction of hydroxyl radicals in aqueous solution with Aldrich humic acid, algae and Fe(III) under high-pressure mercury lamp irradiation

Under a high-pressure mercury lamp (HPML) and using an exposure time of 4 h, the photoproduction of hydroxyl radicals ((OH)-O-.) could be induced in an aqueous solution containing humic acid (HA). Hydroxyl radicals were determined by high-performance liquid chromatography using benzene as a probe. The results showed that (OH)-O-. photoproduction increased from 1.80 to 2.74 muM by increasing the HA concentration from 10 to 40 mg L-1 at an exposure time of 4 h (pH 6.5). Hydroxyl radical photoproduction in aqueous solutions of HA containing algae was greater than that in the aqueous solutions of HA without algae. The photoproduction of (OH)-O-. in the HA solution with Fe(111) was greater than that of the solution without Fe(III) at pH ranging from 4.0 to 8.0. The photoproduction of (OH)-O-. in HA solution with algae with or without Fe(111) under a 250 W HPML was greater than that under a 125 W HPML. The photoproduction of (OH)-O-. in irradiated samples was influenced by the pH. The results showed that HPML exposure for 4 h in the 4-8 pH range led to the highest (OH)-O-. photoproduction at pH 4.0.

Near-infrared luminescence from sol-gel materials doped with holmium(III) and thulium(III) complexes

A series of ternary Ln(tta)(3)L complexes (Ln = Ho, Tm; Htta = 2-thenoyltrifluoroacetone; L = 1,10-phenanthroline, 2,2'-bipyridine, or triphenyl phosphate oxide) and their corresponding sol-gel hybrid materials formed via the in situ synthesis process (designated as Ln-T-L gel) were reported. The complexes and the gels were studied in detail, which suggest the complexes have been successfully synthesized in the corresponding gels.

Solvent extraction study of rare earth elements from chloride medium by mixtures of sec-nonylphenoxy acetic acid with Cyanex301 or Cyanex302

The extraction of rare earth elements from chloride medium by mixtures of sec-nonylphenoxy acetic acid (CA100) with bis(2,4,4-trimethylpentyl) dithiophosphinic acid (Cyanex301) or bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex302) in n-heptane has been studied. The synergistic enhancement of the extraction of lanthanum (III) by mixtures of CA100 with Cyanex301 has been investigated using the methods of slope analysis and constant mole. The extracted complex of lanthanum (III) is determined. The logarithm of the equilibrium constant is calculated as - 1.41. The formation constants and the thermodynamic functions, Delta H, Delta G, and Delta S have also been determined.

Removal of Cr(III, VI) by quaternary ammonium and quaternary phosphonium ionic liquids functionalized silica materials

A series of silica-based organic–inorganic hybrid materials were prepared by the sol–gel process for Cr(III) and Cr(VI) adsorption. These silica materials generally had high surface areas, good physical–chemical stability and high thermal stability. Trialkylmethylammonium bis 2,4,4-trimethylpentylphosphinate ([A336][C272]) and trihexyl(tetradecyl)phosphonium bis 2,4,4-trimethylpentylphosphinate (Cyphos IL 104) were explored as porogens to prepare porous silica and as extractants to extract chromium ions. Cyphos IL 104 and [A336][C272] functionalized silica sorbents (SG-2, SG-5) can be effectively used for the removal of Cr(III) and Cr(VI) from aqueous solutions by adjusting pH values, whereas trialkylmethylammonium chloride (Aliquat 336) and bis(2,4,4-trimethylpentyl)phosphinic acid (Cyanex 272) functionalized silica sorbents (SG-3, SG-4) can only be used for the removal of the single chromium species, Cr(VI) or Cr(III).

Phosphorescence Color Tuning by Ligand, and Substituent Effects of Multifunctional Iridium(III) Cyclometalates with 9-Arylcarbazole Moieties

The synthesis, isomeric studies, and photophysical characterization of a series of multifunctional cyclometalated iridium(III) complexes containing a fluoro- or methyl-substituted 2[3-(N-plienylcarbazolyl)]pyridine molecular framework are presented. All of the complexes are thermally stable solids and highly efficient electrophosphors. The optical, electrochemical, photo-, and electrophosphorescence traits of these iridium phosphors have been studied in terms of the electronic nature and coordinating site of the aryl or pyridyl ring substituents. The correlation between the functional properties of these phosphors and the results of density functional theory calculations was made. Arising from the propensity of the electron-rich carbazolyl group to facilitate hole injection/transport, the presence of such a moiety can increase the highest-occupied molecular orbital levels and improve the charge balance in the resulting complexes relative to the parent phosphor with 2-phenylpyridine ligands. Remarkably, the excited-state properties can be manipulated through ligand and substituent effects that allow the tuning of phosphorescence energies from bluish green to deep red.

A versatile color tuning strategy for iridium(III) and platinum(II) electrophosphors by shifting the charge-transfer states with an electron-deficient core

By fusing an electron-deficient ring system with the phenyl ring of a 2-phenylpyridine (ppy)-type ligand, a new and synthetically versatile strategy for the phosphorescence color tuning of cyclometalated iridium(III) and platinum(II) metallophosphors has been established. Two robust red electrophosphors with enhanced electron-injection/electron-transporting features were prepared by using an electron-trapping fluoren-9-one chromophore in the ligand design. The thermal, photophysical, redox and electrophosphorescent properties of these complexes are reported. These exciting results can be attributed to a switch of the metal-to-ligand charge-transfer (MLCT) character of the transition from the pyridyl groups in the traditional Ir-III or Pt-II ppy-type complexes to the electron-deficient ring core, and the spectral assignments corroborate well with the electrochemical data as well as the timedependent density functional theory (TD-DFT) calculations. The electron-withdrawing character of the fused ring results in much more stable MLCT states, inducing a substantial red-shift of the triplet emission energy from yellow to red for the Ir-III complex and even green to red for the PtII counterpart.