Neuropeptide Y receptors in a protozoaStylonychia mytilus

Radio ligand binding assays(RLBA) were used to study neuropeptide Y (NPY) receptors in a protozoa Stylonychia mytilus. The experimental results showed that 2-3×10+3/mL Stylonychia cells incubated in Pringsheim solution which contained 3H-NPY could specifically bind 3H-NPY and concomitantly present saturable characteristic. This suggested that Stylonychia possessed some specific binding sites for NPY. Scatchard transformations of binding assay for the NPY receptors at 25℃ are compatible with the specific activity of 42.47 fmol/10+3 cells and the binding equilibrium constant of 0.113 nmol/L. The data of 125I-NPY binding assay to the membrane protein extract of Stylonychia indicated that there was a significant difference between the amount of total bound and nonspecific bound of 125I-NPY. This result indicated that NPY receptors were probably localized mainly on the cell membrane.     

Binding of vanadium compounds perturbs conformation and aggregation state of insulin

The interactions between zinc-free insulin and vanadium compounds, NaVO3, VO(acac)2 and VO(ma)2, have been investigated by fluorescence spectroscopy, circular dichroism (CD) and Fourier-transformed infrared (FT-IR) spectroscopy. The results showed that binding of vanadium compounds produced a static quenching of the intrinsic fluorescence of insulin. The apparent association constants were determined to be (0.17±0.01)×104 L*mol-1 for NaVO3, (2.8±0.2)×104 L*mol-1 for VO(acac)2, and (4.0±0.1)×104 L*mol-1 for VO(ma)2, respectively. The light scattering intensity of insulin decreased upon incubation with the vanadium compounds, suggesting the disaggregation of insulin. The attenuation of the band at 273 nm of insulin CD spectra also supported the disaggregation of insulin observed above. A new band at 1650～1653 cm-1 appeared in the FT-IR spectra of insulin upon incubation with the vanadium compounds, indicating the formation of an α-helix structure at B (9-19) motif. This α-helix structure suggests a structural change of insulin from an extended conformation (T state) to a helical conformation (R state), which is essential for binding of insulin to its receptor. In conclusion, binding of vanadium compounds results in conformational changes and disaggregation of insulin. These changes might account for the enhancement of binding affinity for insulin to its receptor in the presence of vanadium compounds.     

Determination of the total concentration of casein and β-lactoglobulin by indirect competitive ELISA in milk and dairy products

The main purpose of this work was to develop an assay as a means of quality control in milk and dairy products. As specific and high abundant proteins in milk and diary products, casein and β-lactoglobulin were chosen as the targets, and an indirect competitive enzyme-linked immunosorbent assay （ELISA） was developed for determination of the total concentration of casein and β-lactoglobulin. The detection limit of the assay was 79.07 ng/mL, and a working range of the calibration curve was from 140.6 to 36,000 ng/mL. The intrassay and inter-assay coefficients of variations were 4.7 % and 6.5 %, respectively. The recoveries ranged from 94.1% to 106.6 %. The developed ELISA assay was used to detect the total con- centration of casein and β-lactoglobulin in liquid milk and milk powder. The results indicated that the developed assay was very specific, and the addition of nonprotein nitrogen （such as melamine, cyanuric acid, and urea） and vegetable protein did not affect the detection. The good performance of the assay makes it suitable for use in the quality control of milk and dairy products.     

Molecular mechanisms of serpin deficiencies

The study of serpin deficiency is currently one of the most active areas in basic medical research. Recently, three hypotheses concerning serpin deficiency have been proposed, which are referred to as the conformational disturbance hypothesis (CDH) , loop-sheet polymerisation hypothesis (LSPH) and multiple binding site hypothesis (MB-SH) . CDH was put forward to explicit serpin deficiency due to conformational change of reactive loop of serpins as a result of mutations occurring away from the reactive site residues and LSPH was to explain deficient serpins due to the formation of polymers. MBSH was proposed to explain the mechanism of the formation of stable enzyme-serpin complex via more than one binding site and blockage or mutation in any of the sites resulting in serpin deficiency. A combination of these mechanisms may be critical in understanding the roles of the many documented mutations and autoimmunities which result in qualitative and quantitative serpin deficiency.     

Effects of protonation and deprotonation on the reactivity of quinolone: A theoretical study

Quinolones are the subject of much research as antibacterial compounds and as a new class of antitumor agents.The protonation(P) and deprotonation(D) sites and conformations of quinolone were investigated.The proton affinity(PA) on each of the possible sites in 4-oxo-1,4-dihydroquinoline has been calculated by the restricted Hartree-Fock(HF) and density functional theory(DFT) methods with the basis set 6-311G**.The O-site of protonation was found to be strongly favored over the N-site for the studied compound in the gas phase.Deprotonation takes place in quinolone by detachment of the N-H and COOH protons.The PA of the simple quinolone molecule was used to characterize quinolone reactivity with DNA binding sites.The relative stabilities of the syn and anti conformations were investigated at the B3LYP/6-311G** level of theory;the syn form was shown to be slightly more stable.Its conformation seems to be intrastabilized by hydrogen-bonds consisting of a hydroxyl proton with the O10 atom as the acceptor.We computed and discussed the charge-density distribution and electrostatic potential to explain the reactivity of quinolone.     

Interaction of aloe-emodin with human serum albumin

The presence of several high affinity binding sites on human serum albumin (HSA) makes it a possible target for many drugs. This study is designed to examine the effect of aloe-emodin on HSA by fluo-rescence, CD spectroscopy and molecular modeling. The results of fluorescence measurements sug-gested that the hydrophobic interaction was the predominant intermolecular force stabilizing the AE-HSA complex, which was in good agreement with the result of molecular modeling study. And the enthalpy change ΔH0 and the entropy change ΔS0 were calculated to be -7.041 kJ·mol-1 and 76.619 J·mol-1·K-1 according to the Van't Hoff equation. The alterations of protein secondary structure in the presence of AE in aqueous solution were quantitatively calculated from CD spectra, and the content of α-helices obviously increased.     

Impacts of Overgrazing and Reclamation on Soil Resources in Rangeland Ecosystems in Huailai Basin, Hebei, China

The soil constituents and relations between the variation of soil resources and plant communities in three adjacent sites representing the overgrazing, reclamation and comparatively undisturbed communities respectively were quantified and examined in study area in Huailal Basin, Hebei Province, China. There have been significantly greater constituent of C, N, P in the soilsof shrubland site. Corg, Ntotal, Navail and Pavail were between 1.18 and 3.90 times more concentrated in the soils of shrubland site in comparison with the other two sites. Although the Ptotal concentration was lower in shrubland soils than inovergrazed rangeland soils, the Parval concentration, however, was significantly greater in the soils of shrubland site, and increased by 59. 1% and even 289.6% in the soils of shrubland site comparing to those in the soils of rangeland and millet field sites. Among the three sites, CV exceeding 40% werefound for SO4 , Cl, and F ion. The CV of organic carbon also exceeded 40% but only in the soils of millet field site. The highest CV were found for F, SO4 ion in the soils of shrubland and overgrazed rangeland sites, while for Cl and SO4 ion in those of millet field site. The results also showed that the introductions of shrubs are of vital importance for the accumulation of soil nutrients and maintenance of soil fertilities, and also for the restoration and reconstruction of desertified ecosystems.     

Manganese (Ⅲ) Acetate:A Versatile Reagent in Organic Chemistry

1 Results Free radical reactions have become increasingly important,as well as a very attractive tool,in organic synthesis within the last two decades,due to their powerful,selective,specific,and mild reaction abilities.Mn(OAc)3 mediated oxidative free radical reactions have been extensively developed in the last twenty years[1,6].Numerous regio-,chemo-,and stereoselective synthetic methods have been developed in both inter-and intramolecular reactions,and have detailed the progress of Mn(OAc)3 mediated oxidative free radical reactions. The selective oxidation of enones led to α′-acetoxy-enones by Mn(OAc)3 oxidation.In general,Mn(OAc)3 oxidations are characterized by higher α′-regioselectivity and chemical yields,and milder reaction conditions,in turn tolerating many sensitive functional groups.The use of Mn(OAc)3 in combination with other carboxylic acids or manganese(Ⅱ) carboxylates extends this methodology to the preparation of a variety of α′-acyloxyenones that are otherwise inaccessible in a one-step procedure.We developed a general method for the synthesis of biaryls starting from arylhydrazines and aromatic solvents in the presence of Mn(OAc)3.We showed for the first time that Mn(OAc)3 is a versatile reagent for the generation of aryl radicals from arylhydrazines.In a subsequent work,we extended this method for the synthesis of heterobiaryls,which was able to be achieved in thepresence of heteroaromatic compounds such as furan and thiophene. Another biaryl coupling reaction starting with arylboronic acids,mediated by Mn(OAc)3,was developed.The treatment of arylboronic acids with Mn(OAc)3 in benzene at reflux temperature afforded the corresponding biphenyl in high yields[7].     

Promoted Cytocompatibility of Silk Fibroin Fiber Vascular Graft through Chemical Grafting with Bioactive Molecules

Natural silk from Bombyx mori has been used as medical sutures for several decades,and regenerated silk fibroin( RSF)based biomaterials have been increasingly studied in the past thirty years. However,vascular graft derived from silk fibroin fiber has been explored in recent several years with development of textile science and engineering. Moreover,endothelialization of vascular graft has been seen as an ideal strategy for preventing thrombosis and getting higher patency in a long term. Therefore,in the present work silk fibroin fiber vascular graft( SF) was chemically grafted with bioactive molecules such as heparin and RSF to improve the cytocompatibility. 3-aminopropyl-triethoxysilane(APTES),1-ethyl-3-(3-dimethylaminopropyl) carbodiie hydrochlide( EDC · HCl),and N-hydroxysuccinimide( NHS) have been employed as coupling agent and crosslinking agents,respectively. Microscopy and ATRFTIR were used to characterize the surface changes and the structure of the grafts after treatment,respectively. Cell culture in vitro and MTT assay were conducted to determine the improvement of cell affinity to the graft. Furthermore,mechanical properties of the grafts before and after treatment were compared. The results showed that the chemical grafting was an effective method for improving the cytocompatibility of SF without significant loss of mechanical properties.     

Investigation on the Copper Content of Matte Smelting Slag in Peirce-Smith Converter

The copper contents and its existing forms in the slags during the slag-making stage of Peirce-Smith converters in Guixi Smelter, Jiangxi Province, China have been investigated. The investigation was based on plant trials with the corresponding thermodynamic calculations and kinetic considerations. From the plant data, the total copper content in the slags was in the range of 2% to 8% (mass fraction). The mechanical entrainment of matte drops has been found to be the main cause of the copper loss. The suspension index, defined as the ratio of the mass fraction of copper in suspended matte drops in the slag to that in bulk of the matte phase, has been adopted to quantify the matte entrainment. The values of this parameter estimated in this work have been found mainly within a range of 2.5%-8.0%. The Fe₃O₄ content in the slag has been estimated to be the most important factor, among others, influencing the separation of slag with matte and, consequently, the copper loss from the slag.     

Identification of proteinaceous binding media for the polychrome terracotta army of Emperor Qin Shihuang by MALDI-TOF-MS

A proteinaceous binding media for the polychrome terracotta army of Emperor Qin Shihuang has been identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry(MALDI-TOF-MS).Methods for the preparation of the model samples and the elimination of interferences have been evaluated,as well as ageing processes.A method involving the complexation of EDTA in combination with dialysis was used to eliminate any interference in the polychrome layers taken from the historical samples.The model samples were aged by being buried in loess to replicate the ageing process of the historical samples as closely as possible.The optimum conditions for the extraction and subsequent enzymatic hydrolysis of the extracted protein were investigated.Under the optimized conditions,the‘‘peptide mass fingerprints’’of the proteinaceous binding media from the historical and model samples were determined by MALDITOF-MS.The results revealed that animal glue was used as the binding media for the polychrome layers of Emperor Qin Shihuang’s terracotta army.It also shows that animal glue used as binding media has a long history in China.     

Interaction of hepatitis B virus with tumor suppressor gene p53: its significance and biological function

The mechanism of the interaction of hepatitis B virus (HBV) with tumor suppressor p53 and its role in the hepatocar-cinogenesis have been studied by PCR-directed sequencing, gel shift assays and in situ ultraviolet cross-linking assay. The biological function of the interaction of HBV with p53 gene was investigated by co-transfection of chloramphenicol acetyltransferase ( CAT) reporter gene. p53 and HBV DNA. and quantitative PCR. Among the 16 primary hepatocellular carcinoma (PHC) samples. 13 were HBV-DNA positive. 10 HBxAg positive and 9 p53 protein positive. The p53 gene point mutation was found in 5 samples, one of which had a G to T substitution located at codon 249. After analyzing the HBV genome by a computer program, a p53 response element binding sequence was found in HBV genome at upstream of enhancer I. from 1047 to 1059 nucleotides. This sequence could specifically bind to p53 protein, increase p53 protein accumulation in the PHC cells and stimulate the transactivating activity of p53 and HBV replication . The results also revealed that HBxAg could combine with p53 protein to form a complex in the cells and enhance CAT expression. Immunocytochemical staining showed that p53 protein complex was located in the cytoplasm and the process of p53 entry to nuclei was. in part, blocked. From our results, we conclude that the mutation of p53 gene at codon 249 is infrequent in HBV-associated PHC. the DNA-protein binding between HBV and p53. and the protein-protein binding between HBxAg and p53 might lead to the reduction or inactivation of p53 protein, which in turn resulting in HBV-associated hepatocarcinogenesis.     

Distribution of lanthanum among the chloroplast subcomponents of spinach and its biological effects on photosynthesis： location of the lanthanum binding sites in photosystem Ⅱ

The effects of lanthanum at different concentrations on the related photosynthetic activities of Hill reaction, Mg^2＋-ATPase and Ca^2＋-ATPase in spinach chloroplast were studied. Experimental results showed that lanthanum can increase all the activities at suitable concentration （15-30 mg· L^-1）, however, it behaves toxically on them when over used （60 mg. L^-1）. To get an improved understanding of the mechanism of lanthanum effects on the photosynthesis of spinach, the different subcomponents in the chloroplast of the cultured spinach were isolated, and the content of lanthanum in each subcomponent was determined by ICP-MS. The results obtained indicated that among these different subcomponents, about 90% out of the total chloroplast lanthanum was located in photosystem Ⅱ （PS Ⅱ） while there was little lanthanum in photosystem Ⅰ （PS Ⅰ）. Moreover, size exclusion high performance liquid chromatography （SE-HPLC） coupled with online UV and ICP-MS detections was novelly used for locating lanthanum binding sites in PS Ⅱ proteins for the first time. It was found that lanthanum has two binding sites in PS Ⅱ： La associates with chlorophyll together with magnesium in PS Ⅱ by partly replacing magnesium and also shares the common binding sites of PS Ⅱ proteins together with the inorganic cofactors of calcium and manganese, influencing the process of photosynthesis.     

Cloning and analysis of a γ-tocopherol methyltransferase gene from Brassica oleracea and the function of its recombinant protein

The full-length cDNA (BoTMT) of γ-TMT is obtained from Brassica oleracea by 3′- and 5′-RACE methods. The 1265 bp cDNA contains an open reading frame of 1044 bp, which encodes a protein of 347 amino acids with a predicted chloroplast transit peptide and two S-adenosylmethionine (SAM)-binding domains. Sequence analysis shows that the deduced protein shares 41.8%～86.5% similarity to known γ-TMTs. Semi-quantitative RT-PCR reveals that BoTMT is expressed preferentially in flowers and leaves of B. oleracea. The recombinant γ-TMT protein is obtained by cloning its encoding region into the prokaryotic expression vector pET30a. The protein expressed in E. coli accounts for 22% of total bacterial protein. The enzyme activity assay indicates that the recombinant protein has relatively high activity to convert γ-tocopherol to α-tocopherol in vitro.     

Binding and endocytosis of monoterbium transferrin by K562 cells

Human serum apotransferrin is the major iron-tran- sport protein in blood. The protein binds iron as Fe3+ at two similar, but not identical, high-affinity binding sites. Although iron bound to human serum apotransferrin is less then 0.1% (~3 mg) of the total body iron, dynamically it is the most important iron pool with the highest rate of turnover. The turnover of transferrin iron is in the order of 30 mg per day and, normally, about 80% of this iron are transported to the bone marrow for hem…     

Effect of Residue Mutation on the Electrostatic Potential in EcCIC

The effect of mutation of strongly conserved porelining residues in the chloride channel EcClC on the electrostatic potential and binding free energy of the chloride ion was studied using explicit protein-membrane structures. Electrostatic potential distribution and binding free energy of the chloride ion at different binding sites in the wild-type and mutated EcClC were calculated with APBS. The potential data reveal that the electrostatic potential around the selectivity filter, especially around the site Sext and Scen becomes more negative as the residue R147 was mutated to C147. The electrostatic binding free energy shows that the binding free energy of the chloride ion at all binding sites becomes more positive as R147 was mutated. It follows that mutation of R147 decreases ion stabilization at binding sites and affects channel＇s gating.     

Special IR properties of palladium nanoparticles and their aggregations in CO molecular probe infrared spectroscopy

Dispersed Pd nanoparticles (Pdn) have been synthesized by reducing H2PdCI4 with ethanol, and stabilized using poly(vinylpyrrolidone) (PVP). The Pdn is applied to the glassy carbon substrate to form a thin film, and then the potential cyclic scanning at 50 mV.s^-1 from -0.25 to 1.25 V was carried out for about 30 min to form the aggregations of Pdn (Pdn^ag). FTIR spectroscopy of both transmission and reflection modes was employed to study CO adsorption on Pdn and Pdn^ag in both solidlliquid and solidlgas interfaces. It has been revealed that CO adsorption on Pdn film yields two IRbands near 1964 and 1906 cm-1, which are assigned to IR absorption of CO bonded on asymmetric and symmetric bridge sites, respectively. In contrast to the IR properties of CO adsorbed on Pdn, only species of CO bonded on asymmetric bridge sites was determined on Pdn^ag, and the direction of the IR band near 1963 cm^-1 is completely inverted. The full width at half-maximum (FWHM) of the COB^as band near 1964 cm^-1 is measured to be 14 cm^-1 on Pdn film, while it is 24 cm^-1 on Pdn^ag film. The results of the present study demonstrated that the inverting of the IR band direction is a general phenomenon that is closely related to the interaction between nanoparticles in aggregation of Pdn.