[en] Rare earth products have used largely in the field of industry and agriculture, especially in agriculture.The application of Ln-products with organic radical, like Ln-citrate in animal husbandry have been developed at China from 20 years ago. And now, Western Europe countries have been used Ln-products in animal husbandry in order to enhance animal growth and ability for resistance of diseases.Ln-citrate was synthesized from the Ln-carbonate obtained by processing Dong Pao ore by technological flow-sheet such as: Dissolution of rare earth carbonate by HCl of 15%; Precipitation of rare earth hydroxide by NH₄OH of 8%; Washing of rare earth hydroxide by water; Dissolution of rare earth hydroxide by citric acid of 4M; Synthesization of rare earth citrate was impacted by temperature, time and concentration of citric acid. Experiments were conducted and parameters of process have been determined: temperature of 90℃ ; time of reaction 5h; acid concentration of 4M and the efficiency of process 95% (author)

No abstract available

[en] The molecule of uracil-DNA glycosylase from M. tuberculosis exhibits domain motion on binding to DNA or a proteinaceous inhibitor. The highly conserved DNA-binding region interacts with a citrate ion in the structure. Uracil N-glycosylase (Ung) is the most thoroughly studied of the group of uracil DNA-glycosylase (UDG) enzymes that catalyse the first step in the uracil excision-repair pathway. The overall structure of the enzyme from Mycobacterium tuberculosis is essentially the same as that of the enzyme from other sources. However, differences exist in the N- and C-terminal stretches and some catalytic loops. Comparison with appropriate structures indicate that the two-domain enzyme closes slightly when binding to DNA, while it opens slightly when binding to the proteinaceous inhibitor Ugi. The structural changes in the catalytic loops on complexation reflect the special features of their structure in the mycobacterial protein. A comparative analysis of available sequences of the enzyme from different sources indicates high conservation of amino-acid residues in the catalytic loops. The uracil-binding pocket in the structure is occupied by a citrate ion. The interactions of the citrate ion with the protein mimic those of uracil, in addition to providing insights into other possible interactions that inhibitors could be involved in

[en] Highlights: • This is the first structure of 1,2-HQD from Gram-negative bacterium P. putida DLL-E4. • The Fe(III) is pentacoordinated by a typical His₂Tyr₂, the citrate anion and one water molecule. • Asp80, Thr81 and Val248 are responsible for the substrate specificity of PnpC. • The N-terminal α-helix of PnpC is necessary for its soluble expression and enzyme catalysis. Hydroxyquinol 1,2-dioxygenase is a key enzyme in the hydroxyquinol pathway of p-nitrophenol (PNP) degradation, and catalyzes the ring cleavage of benzenetriol to maleylacetate. Here, we report the first structure of a hydroxyquinol 1,2-dioxygenase from the Gram-negative bacterium Pseudomonas putida DLL-E4 (PnpC) at the resolution of 2.1 Å. The tertiary structure of PnpC resembles that of the homologous intradiol dioxygenases. The catalytic Fe(III) is pentacoordinated by the conserved Tyr160, Tyr194, His218 and His220, the citrate anion and one water molecule. Among the residues expected to interact with the substrate, structural comparison with the (chloro)catechol dioxygenases suggested that Asp80, Thr81 and Val248 are responsible for the substrate specificity. Moreover, truncation of the N-terminal α-helix of PnpC suggested the N-terminal domain is required for its soluble expression and enzyme catalysis. Our results might provide insights in the substrate recognition and rational design of this enzyme class to be used in bioremediation.

[en] A new sensitized cofluorescence system has been developed for the determination of Eu(III) based on its complex formation with tetracycline (TC) in the presence of citrate and Tb(III). Eu(III) forms complex with tetracycline in alkaline condition which emits intrinsic fluorescence of Eu(III) when excited. The fluorescence intensity of Eu(III)- TC is enhanced about 5 times when citrate and Tb(III) are introduced. The factors that influence the fluorescence intensity of the system have been studied in detail. Under optimum conditions, the relative fluorescence intensity is linear in over the range 6.0x10^-9 to 4.0x10^-6 M of Eu(III). The detection limit has been found to be 1.4x 10^-9 M of Eu(III). The method has been used for the determination of Eu in two rare earth samples with relative error 4.5% and -1.8%, and RSD 2.6% and 2.1%, respectively. (author)

[en] Complete text of publication follows. Many methodologies exist for the speciation analysis of As in water samples. Selective reduction procedure based on the highly pH-dependent reaction between arsenic species and NaBH4 to generate arsine in HG AAS system is relatively commonly used. In this case, for As(V) strongly acidic solution is required (pH ≤ 1), while for As(III) hydride formation occurs in mildly acidic solutions. The aim of this study was to critically evaluate the most frequently used reaction media for the speciation analysis of arsenite in the presence of arsenate. Five different reaction media has been used to achieve a selective volatilization of arsenite: 1.5 M HCl (pH <1.0), 0.1 M acetic acid (pH ∼2.9), citrate buffer (pH ∼3.1), acetate buffer (pH ∼5.0) and phosphate buffer (pH ∼7.2). All the studied reaction media can be used for the selective volatilization of As(III) but the serious problem caused by the interference of As(V) was observed (in 0.1 M acetic acid, citrate buffer and acetate buffer) when relative content of As(III) was less than 10% (from all the present arsenic). Natural waters usually contain less than 10% of As(III), so speciation in the real samples should be accompanied with another speciation analysis procedure to confirm the accuracy of obtained data. This problem was not observed in phosphate buffer but in this case the sensitivity was significantly lower and the speciation analysis in this medium can be done only if relatively high contents of As(III) in the samples are present. The work was supported by Slovak Research and Development Agency under the contracts No. APVT-20-010204, LPP-0038-06, LPP-0188-06, LPP-0146-09 and SK-CZ-0044-07, by Scientific Grant Agency of Ministry of Education of Slovak Republic and the Slovak Academy of Sciences under the contracts No. VEGA 1/4463/07, VEGA 1/4464/07 and VEGA 1/0272/08 and by Ministry of Education, Youth and Sports of Czech Republic under the contract No. MEB 080813.

[en] Gallium-67 citrate has been evaluated in six patients diagnosed to have acute pancreatitis based on clinical picture, urine and serum amylase level, Ultrasanography and CT scan findings. The diagnosis of acute pancreatitis was confirmed by gallium-67 scan in four patients (True positive). One of them showed evidence of acute cholecysitis and pancreatitis. No gallium uptake was detected in the region of pancreas in the other two (True negative). Repeated gallium scan in two of the true positive patients showed decreased gallium concentration in the pancreas in response to medical treatment. The scan became normal in one of these two after four weeks. We conclude that gallium-67 scintigraphy is useful to determine extent and severity of acute pancreatitis and in following the response to medical treatment. Gallium (⁶⁷Ga) has been under utilised in acute pancreatitis. The aim of the present study is to find the value of gallium-67 scintigraphy in determining the extent and severity of acute pancreatitis at the initial diagnosis and for follow up of medically treated patients. (Author)

[en] Citrate synthase from the thermophilic euryarchaeon T. acidophilum fused to a hexahistidine tag was purified and biochemically characterized. The structure of the unliganded enzyme at 2.2 Å resolution contains tail–active site contacts in half of the active sites. Citrate synthase (CS) plays a central metabolic role in aerobes and many other organisms. The CS reaction comprises two half-reactions: a Claisen aldol condensation of acetyl-CoA (AcCoA) and oxaloacetate (OAA) that forms citryl-CoA (CitCoA), and CitCoA hydrolysis. Protein conformational changes that ‘close’ the active site play an important role in the assembly of a catalytically competent condensation active site. CS from the thermoacidophile Thermoplasma acidophilum (TpCS) possesses an endogenous Trp fluorophore that can be used to monitor the condensation reaction. The 2.2 Å resolution crystal structure of TpCS fused to a C-terminal hexahistidine tag (TpCSH6) reported here is an ‘open’ structure that, when compared with several liganded TpCS structures, helps to define a complete path for active-site closure. One active site in each dimer binds a neighboring His tag, the first nonsubstrate ligand known to occupy both the AcCoA and OAA binding sites. Solution data collectively suggest that this fortuitous interaction is stabilized by the crystalline lattice. As a polar but almost neutral ligand, the active site–tail interaction provides a new starting point for the design of bisubstrate-analog inhibitors of CS

[en] Gold nanoparticles (Au NPs) were synthesized by the citrate reduction method. The evolution of NP size and morphology was closely studied by varying temperature and citrate to gold precursor (Na₃Ct/HAuCl₄) ratio. The reaction temperatures below 100 °C were mainly studied. A Na₃Ct/HAuCl₄ ratio range of 1.25:1 to 4.33:1 was the focus of our investigation. The NP size and morphology was strongly influenced by the Na₃Ct/HAuCl₄ ratio, while the temperature played a subtle role. The reaction times were also monitored. The higher concentration samples required almost an order of magnitude longer reaction time compared to the low concentration samples. (paper)

[en] The development of techniques that could be useful in fields other than biological warfare agents countermeasures such as medical diagnostics, industrial microbiology, and environmental applications have become a very important subject of research. Raman spectroscopy can be used in near field or at long distances from the sample to obtain fingerprinting information of chemical composition of microorganisms. In this research, biochemical components of the cell wall and endospores of Bacillus thuringiensis (Bt) were identified by surface-enhanced Raman scattering (SERS) spectroscopy using silver (Ag) nanoparticles (NPs) reduced by hydroxylamine and borohydride capped with sodium citrate. Activation of hot spots, aggregation and surface charge modification of the NPs, was studied and optimized to obtain signal enhancements from Bt by SERS. Slight aggregation of the NPs as well as surface charge modification to a more acidic ambient was induced using small-size borohydride-reduced NPs in the form of metallic suspensions aimed at increasing the Ag NP-Bt interactions. Hydroxylamine-reduced NPs required slight aggregation and no pH modifications in order to obtain high spectral quality results in bringing out SERS signatures of Bt.