Species of rare earth(III) and calcium(II) in the presence of L-aspartic acid and L-arginine

Rare earth (III)-Asp-Arg and Ca(II)-Asp-Arg systems were studied by potentiometric titration under physiological conditon. The species of each system were determined. The distribution of Tb (III) and Ca(II) species was discussed, as well as in the quaternary system of Tb(III)-Ca(II)-Asp-Arg.

Isobutane/butene alkylation over supported heteropoly acid catalysts: I. Influence of the structure of silica

Catalysts consisting of heteropoly acids (HPAs) supported on different silica and mesoporous molecular sieves have been prepared by impregnation and the sol-gel method, respectively, and their catalytic behavior in fixed-bed alkylation of isobutane with butene has been investigated. The activity, selectivity and stability of the supported-HPA catalysts could be correlated with the surface acidity of the catalysts, the structure of supports as well as the time on stream (TOS). In the fixed-bed reactor, the acidity of the heteropoly acid is favorable to the formation of dimerization products (C-8(=)); especially, the pore size of supports was seen to have an important effect on activity and product distribution of the catalysts. Contrary to the traditional solid-acid catalysts, the supported-HPA catalysts own an excellent stability for alkylation, which makes it possible for these supported catalysts to replace the liquid-acid catalysts used in industry.

Extraction and separation of heavy rare earth (III) with Extraction Resin containing di(2,4,4-trimethyl pentyl) phosphinic acid (Cyanex 272)

Extraction resins, of the type of;levextrel, (which is a collective term for styrene/divinylbenzene based copolymers of predominantly macroporous structure that contain a selective extractant) are important for the recovery and separation of metal ions, as they combine features of solvent extraction and ion exchange resins. This paper presents the results of the adsorption of heavy rare earth ions (Ho(III), Er(III), Tm(III), Yb(III), Lu(III) and Y(III)) from hydrochloric acid solutions at 0.2 mol/L ionic strength and 50 degrees C by the extraction resin containing di (2,4,4-trimethyl pentyl) phosphinic acid (Cyanex 272) and the chromatographic separation of (Er(III), Tm(III) and Yb(III)). Technological separation products, with purity and yield of Tm2O3 >99.97%, >80%, Er2O3 >99.9%, >94% and Yb2O3 >99.8%, >80% respectively, have been obtained from a feed having the composition Tm2O3 60%, Er2O3 10%, and Yb2O3 3%, the others 27%. The distribution coefficients, extraction equilibrium constants and separation factors have been determined as a function of acidity, loading of the resin and rare earths, flow rates and column ratios. The resolutions and efficiencies of separation of Er/Tm/Yb each other have been calculated. The stoichiometry of the extraction of rare earth ions has been suggested as well.

Tb(111) and Ca(11) ion equilibria in the presence of glutamic acid and glutamine

Tb(111) and Ca(11) ion equilibria in the Presence of glutamic acid and glutamine were studied by potentiometric titration at 37 degrees C and an ionic strength of 0.15mol/L(NaCl). The stability constants for Tb(111) and Ca(11) complexes in the systems were obtained. The species and their distribution in the systems were discussed.

STUDIES ON THE COORDINATION OF TB(III) AND CA(III) WITH AMINO-ACID UNDER THE PHYSIOLOGICAL CONDITION

Tb(Ca)-glycine, Tb(Ca)-alanine, Tb(Ca)-glycine-alanine systems were studied by potentiometry (37%, I = 0.15 mol/L NaCl). The stability constants of complexes and distribution of species in ternary system were obtained. The results show CaTb for the ternary complexes. The species convert each other with changing pH values.

THE CHAIN STRUCTURE AND LIGHT-SCATTERING-STUDIES FOR ACRYLAMIDE-SODIUM ACRYLIC-ACID (AM-AA) COPOLYMERS

A set of AM-AA copolymer samples with the same comonomer content and different average molecular weight have been characterized by C-13 NMB and light scattering methods in this paper. The chemical composition (comonomer AA, mole content 16.9 +/- 1.1%) of these samples is uniform. the sequence of AA in the macromolecular chain is of alone and random distribution and the light scattering theory from polyelectrolyte in added-salt solutions is suitable for the AM-AA copolymers-0.12 mol/L NaCl water systems. The actual values of M(w), the second Virial coefficient A(2) and the mean square radius of gyration (R(2)), for the studied samples have been obtained. The relationships between the molecular parameters are as follows: A(2)=0.0619 ($) over bar M(w)(-0.24), < R(2) >(1/2)(t)= 0.0210 ($) over bar M(w)(0.54).

RELATIONSHIP OF THE SEQUENCE DISTRIBUTION OF A POLYMER TO THE CATALYTIC ACTIVITY OF ITS ND COMPLEX

The sequence distribution of the monomeric units in the styrene-acrylic acid copolymer has been obtained by calculation. The probability of long sequences of styrene increases with an increase in the content of the monomer in the copolymer. The highest distribution of short sequences of styrene takes place for the copolymer containing equimolecular amounts of styrene and acrylic acid. The copolymer which has this latter structure is inadequate for the synthesis of highly active supported complexes. When the distributions of long and short sequences of styrene are approximately equal, the activity of the Nd and Fe prepared polymer complexes is higher.

Positional distribution of fatty acids on the glycerol backbone during the biosynthesis of glycerolipids in Ectocarpus fasciculatus

The biosynthesis of glycolipids in E. fasciculatus was studied by C-14 label and chase. The fatty acids in sulphoquinovosyl diacylglycerol (SQDG) were almost 16-carbon and 18-carbon ones. In addition to the two fatty acids, monogalactosyl diacylglycerol (MGDG) and digalactosyl diacylglycerol (DGDG) contained 8.5 mol% and 31.0 mol% of eicosapentaenoic acid (20 : 5), respectively, and this fatty acid was usually distributed in the sn-1 position of the glycerol backbone. When plants were incubated with [2-C-14] acetate, differences existed in the positional distribution of the labeled fatty acids in sn-1 and sn-2 among the three glycerolipids. In SQDG C-14-labeled fatty acids were distributed uniformly in the sn-1 and sn-2 positions. In DGDG, C-14-labeled fatty acids were mainly distributed in the sn-2 position. In MGDG, the radioactivity of fatty acids in sn-1 position was far greater than that in sn-2 position after a 30 min pulse label, and the difference in radioactivity between the two positions decreased rapidly. The above results indicated that differences in the positional distribution of C-14-labeled fatty acids between sn-1 and sn-2 positions might be related to 20 : 5 and the biosynthesis of DGDG. Our results also suggested that E. fasciculatus had the same DGDG biosynthetic pathway as that in higher plants and galactosyl transferase was selective for MGDC.

The mitochondrial manganese superoxide dismutase gene in Chinese shrimp Fenneropenaeus chinensis: Cloning, distribution and expression

Manganese superoxide dismutase (MnSOD) plays an important role in crustacean immune defense reaction by eliminating oxidative stress. Knowledge on MnSOD at molecular level allows us to understand its regulatory mechanism in crustacean immune system. A novel mitochondrial manganese superoxide dismutase (mMnSOD) was cloned from hepatopancreas of Chinese shrimp Fenneropenaeus chinensis by 3' and 5' rapid amplification of cDNA ends (RACE) PCR. The full-length cDNA consists of 1185 bp with a 660 bp open reading frame, encoding 220 amino acids. The deduced amino acid sequence contains a putative signal peptide of 20 amino acids. Sequence comparison showed that the mMnSOD of F. chinensis shares 88% and 82% identity with that of giant freshwater prawn Macrobrachium rosenbergii and blue crab Callinectes sapidus, respectively. mMnSOD transcripts were detected in hepatopancreas, hemocytes, lymphoid organ, intestine, ovary, muscle and gill by Northern blotting. RT-PCR analysis indicated that mMnSOD showed different expression profiles in shrimp hemocytes and hepatopancreas after artificial infection with while spot syndrome virus (WSSV). In addition, a fusion protein containing mMnSOD was produced in vitro. LC-ESI-MS analysis showed that two peptide fragments (-GDVNTVISLAPALK- and -NVRPDYVNAIWK-) of the recombinant protein were identical to the corresponding sequence of M. rosenbergii mMnSOD, and the enzyme activity of the refolded recombinant protein was also measured. (c) 2006 Elsevier Ltd. All rights reserved.

Distribution of calcifying and silicifying phytoplankton in relation to environmental and biogeochemical parameters during the late stages of the 2005 North East Atlantic Spring Bloom

The late stage of the North East Atlantic (NEA) spring bloom was investigated during June 2005 along a transect section from 45 to 66 degrees N between 15 and 20 degrees W in order to characterize the contribution of siliceous and calcareous phytoplankton groups and describe their distribution in relation to environmental factors. We measured several biogeochemical parameters such as nutrients, surface trace metals, algal pigments, biogenic silica (BSi), particulate inorganic carbon (PIC) or calcium carbonate, particulate organic carbon, nitrogen and phosphorus (POC, PON and POP, respectively), as well as transparent exopolymer particles (TEP). Results were compared with other studies undertaken in this area since the JGOFS NABE program. Characteristics of the spring bloom generally agreed well with the accepted scenario for the development of the autotrophic community. The NEA seasonal diatom bloom was in the late stages when we sampled the area and diatoms were constrained to the northern part of our transect, over the Icelandic Basin (IB) and Icelandic Shelf (IS). Coccolithophores dominated the phytoplankton community, with a large distribution over the Rockall-Hatton Plateau (RHP) and IB. The Porcupine Abyssal Plain (PAP) region at the southern end of our transect was the region with the lowest biomass, as demonstrated by very low Chla concentrations and a community dominated by picophytoplankton. Early depletion of dissolved silicic acid (DSi) and increased stratification of the surface layer most likely triggered the end of the diatom bloom, leading to coccolithophore dominance. The chronic Si deficiency observed in the NEA could be linked to moderate Fe limitation, which increases the efficiency of the Si pump. TEP closely mirrored the distribution of both biogenic silica at depth and prymnesiophytes in the surface layer suggesting the sedimentation of the diatom bloom in the form of aggregates, but the relative contribution of diatoms and coccolithophores to carbon export in this area still needs to be resolved.

Synthesis of 2-butoxy ethanol with narrow-range distribution catalyzed by supported heteropolyacids

A supported heteropolyacid (HPA), H3PMo12O40/SiO2, calcined in vacuum at 150 degrees C, has been shown to be an efficient solid acid catalyst for the synthesis of 2-butoxy ethanol with high selectivity. (C) 2000 Elsevier Science B.V. All rights reserved.

A novel method to synthesize amorphous silica-alumina materials with mesoporous distribution without using templates and pore-regulating agents

In this study, a novel sol-gel method is used to synthesize amorphous silica-alumina materials with a narrow mesoporous distribution and various Si/Al molar ratios without using any templates and pore-regulating agents. During the preparation procedure, only inexpensive inorganic salts were used as raw materials, instead of expensive and harmful alkoxides. The precursor sol was dried at room temperature in a vacuum box kept at 60 mmHg until it began to form the gel. The results of a nitrogen sorption experiment indicate that the synthesized materials with different Si/Al molar ratios have similar mesoporous distributions (within 2-12 nm). Moreover, it was found that the material's pore size distribution remains at a similar value during the heat treatment from room temperature to 550 degreesC. On the basis of the nitrogen sorption, TEM, and AFM characterization results, a formation mechanism of mesopores which accounts for the experimental data is also suggested. This suggested mechanism involves rearrangement of the primary particles during the drying process to form the precursors of the similarly sized mesopores. The synthesized materials were characterized by XRD, thermal analysis (TG/DTA), Al-27 and Si-29 MAS NMR spectroscopy, SEM, TEM, and AFM. The results of Al-27 and 29Si MAS NMR indicate that the distribution of silicon and aluminum in the synthesized materials is more uniform and homogeneous than that in the mixed oxides prepared via the traditional sol-gel method even at high alumina contents. The type and density of the acid sites were studied using pyridine adsorption-desorption FTIR spectroscopy. It was shown that the acidity of the synthesized materials is higher than that of the silica-alumina materials prepared by conventional methods.

Sol-gel derived oxides and mixed oxides catalysts with narrow mesoporous distribution

A novel sol-gel process for preparing oxides and mixed oxides sols from precipitation and peptization process is reported in this article. Inorganic salts are used as raw materials in this study. It is found that the amount of acid has great influence on the stability and particle diameter distribution of the precursor sols. Ultrasonic treatment is used to prepare alumina sol at room temperature. The result of Al-27 NMR shows that there exist Al-13(7+) species in the sol. By controlling the sol particles with narrow particle diameter distribution, alumina, titania and silica-alumina (SA) materials with narrow mesoporous distribution are formed by regular packing of sol particles during gelation without using any templates. The results also show that the structure and particle diameter distribution of precursor sol determine the final materials' texture.

Stereocomplexed poly(lactic acid)-poly(ethylene glycol) nanoparticles with dual-emissive boron dyes for tumor accumulation.

Responsive biomaterials play important roles in imaging, diagnostics, and therapeutics. Polymeric nanoparticles (NPs) containing hydrophobic and hydrophilic segments are one class of biomaterial utilized for these purposes. The incorporation of luminescent molecules into NPs adds optical imaging and sensing capability to these vectors. Here we report on the synthesis of dual-emissive, pegylated NPs with "stealth"-like properties, delivered intravenously (IV), for the study of tumor accumulation. The NPs were created by means of stereocomplexation using a methoxy-terminated polyethylene glycol and poly(D-lactide) (mPEG-PDLA) block copolymer combined with iodide-substituted difluoroboron dibenzoylmethane-poly(L-lactide) (BF2dbm(I)PLLA). Boron nanoparticles (BNPs) were fabricated in two different solvent compositions to study the effects on BNP size distribution. The physical and photoluminescent properties of the BNPs were studied in vitro over time to determine stability. Finally, preliminary in vivo results show that stereocomplexed BNPs injected IV are taken up by tumors, an important prerequisite to their use as hypoxia imaging agents in preclinical studies.

The G-protein-coupled receptor phosphatase: a protein phosphatase type 2A with a distinct subcellular distribution and substrate specificity.

Phosphorylation of G-protein-coupled receptors plays an important role in regulating their function. In this study the G-protein-coupled receptor phosphatase (GRP) capable of dephosphorylating G-protein-coupled receptor kinase-phosphorylated receptors is described. The GRP activity of bovine brain is a latent oligomeric form of protein phosphatase type 2A (PP-2A) exclusively associated with the particulate fraction. GRP activity is observed only when assayed in the presence of protamine or when phosphatase-containing fractions are subjected to freeze/thaw treatment under reducing conditions. Consistent with its identification as a member of the PP-2A family, the GRP is potently inhibited by okadaic acid but not by I-2, the specific inhibitor of protein phosphatase type 1. Solubilization of the membrane-associated GRP followed by gel filtration in the absence of detergent yields a 150-kDa peak of latent receptor phosphatase activity. Western blot analysis of this phosphatase reveals a likely subunit composition of AB alpha C. PP-2A of this subunit composition has previously been characterized as a soluble enzyme, yet negligible soluble GRP activity was observed. The subcellular distribution and substrate specificity of the GRP suggests significant differences between it and previously characterized forms of PP-2A.