Synthesis of novel organophosphorus C60 dimers

DUE TO THEIR OUTSTANDING PHYSICAL AND CHEMICALPROPERTIES,FULLERENE DIMERS HAVE PROVEN TO BE ATTRACTIVENANO-SCALE ORGANIC COMPOUNDS IN VARIOUS FIELDS SUCH ASNONLINEAR OPTICS,ORGANIC MATERIALS,BIOLOGY AND MEDI-CINE[1].AMONG THE FULLERENE DIMERS THAT HAVE BE…     

Down-regulation of αGal epitopes by co-transfection of α1,3-galactosidase gene and α1,2–fucosyltransferase gene

The polycarbohydrate structure of Galα1- 3Ga1β1-4GluNAc-R （known as αGal epitopes of xenoantigen）, produced by α1-3-galactosyltransferase （α1,3-GT） in the course of animal development, is the major xenoantigen on the cell surface of porcine which causes hyperacute rejection in pig-to-human xenotransplantation. Alpha-1,3-galactosidase （AGL）, a hydrolytic enzyme, can remove the terminal α1,3-galactosyi from the Galα1-3Galβ1-4GluNAc-R structure resulting in cleaning αGai epitopes from the porcine cells. Aipha-1,2-fucosyitransferase （HT） can modify the surface carbohydrate phenotype of porcine cells, bringing about reduction of αGai epitopes expression. In this study, human AGL and HT gene were co-transfected to porcine fetal fibroblast （PFFb） in equimolar concentration to reduce the xenoantigen. Gene and protein of hAGL and HT were both detected to express at high level by RT-PCR and Western blot, respectively. There was an 84% reduction in αGai xenoantigen and an 82% increase in H antigen as assayed by flow cytometry in the AGL and HT gene co-transfected PFFb. The number and morphology of transgenic PFFb chromosome were normal. Findings indicate that Galα1-3Gal epitopes of PFFb could be down regulated by AGL and HT co-transfection without deleterious effects on the chromosomal profile of the transgenic ceil.     

Interaction between integrin αIIbβ3 and synthesized cyclic hexapeptide containing RGD

The RGD sequence generally exists in the extracellular matrix proteins and can be recognized by many integrin proteins. The binding ability of immobilized biotinylated cyclic hexapeptide [cyclo(-Arg-Gly-Asp-D-Phe-Lys-Gly-)] containing RGD to integrin α_αbβ₃ was tested by the methods of ELISA and SPR. Results showed that a spacer of 1.48–2.2 nm between the peptide and the biotin residue was long enough to send the RGD sequence into the binding center embccedded within α_IIbβ₃, and the equilibrium dissociation constant was 1.1 μm. The work provides an ideal model system for the research of cell adhesion on solid surfaces.     

Electrophysiological research of synapse formation from beginning to maturity

The development of synapses is an important question in neurobiology. We employ patchclamp technique to record MEPCs and EPCs of myoballs inXenopus cell culture. The rate of EPC/MEPC is related with synapses maturation. Accordingly, we define the mature synapses as those whose rate of presynaptic membrane ’ s EPC to MEPC is more than 8. The process of maturation needs about 2–5 h after neuntes contact with myoballs. We divide the development of synapses into three stages: young, developing and mature. The neurotransmitters stack gradually and increase by hundreds of times along with young synapses growing into maturity. So the process of synapses maturation should include presynaptic membrane specialization, postsynaptic membrane specialization and neurotransmitters stack.     

α-LTX and α-LTXN4C induce [Ca2+]i elevation through different mechanisms in pancreatic β cells

α-latrotoxin (α-LTX) is the only neurotoxin from black-widow spider which has secretagogue effects in the vertebrates. It causes massive neurotransmitter and hormone release via two instinct mechanisms after binding with its high-affinity membrane recep…     

Geochemical characteristics and applications of 18a (H)-neohopanes and 17a (H)-diahopanes

Distributions and geochemical significances of 18α(H)-neohopanes and of 17α(H)-diahopanes in oils from west Xialiaohe depression of the Bohai Bay Basin have been studied. Relative abundance of 18α(H)-neohopanes and of 17α(H)-diahopanes can be effectively used as maturity parameters, in a range of medium-high mature stage, based on consideration on sedimentary-organic facies of source rocks. With a dual geochemical significance of maturity and sedimentary-organic facies, neohopane and diahopane parameters can be well used in oil-source correlation and in petroleum population division. Formation, primary concentration and preservation of precursors of rearranged hopanes are closely related to depositional conditions such as Eh-pH and clays content. A series of probable diahopanes (series D) was detected in the oils, which exhibits a similar distribution pattern and geochemical behavior as that of 17α(H)-diahopanes (series B).     

Different patterns of agonist-induced modulation of α1B-adrenoceptor density at different initial expression levels

We compared the norepinephrine (NE) induced α_1B-adrenoceptor (α_1B-AR) expression modulation between two transfected human embryonic kidney (MEK) 293 cell lines in which α_1B-AR densities were (6 336 ± 913) and (773 ± 164) fmol ▪ mg¹, respectively. Treatment of cells with NE (10 μmol ▪ L₁) for 48 h decreased high-level expressed α_1B-AR density, but increased low-level expressed α_1B-AR density. The protein kinase C inhibitor Calphostin C or Ro-31-8220 reversed, and its activator PMA mimicked the NE-induced down-regulation of high-level expressed α_1B-AR. Moreover, PMA induced a down-regulation of low-level expressed α_1B-AR. The endoplasmic reticulum Ca²⁺-ATPase inhibitor cyclopiazonic acid (CPA) and the calcium chelator BAPTA/AM did not affect the down-regulation of high-level expressed α_1B-AR, but inhibited the up-regulation of low-level expression α_1B-AR induced by NE. These results suggest that α_1B-adrenoceptor densities at different initial expression levels are differentially regulated by NE and their signal transduction pathways are different.     

Tautomerizations and intramolecular hydrogen bondings of the chiral α-nitroester, α-nitrosoester and α-ketoester

Interesting and diverse tautomerizations and intramolecular hydrogen bondings of the chiral α-nitroester, α-nitrosoester and α-ketoester are described and rationally interpreted.     

Morphological characteristics of α-Al2O3 crystallites obtained direct1y from hydro /solvothermal solvents

The morphological characteristics of α-Al₂O₃ crystallites obtained directly from hydro/solv othermal solvents are reported and the formation mechanisms of corundum morphology are discussed from crystal growth and crystal chemistry principles. The crystal growth process is considered as a process of incorporation of growth units on the growth interfaces, and the crystal morphology is determined by the linkage of the coordinated polyhedra.     

Surface interactions of MoO3/ α-Fe2O3 system

α-Fe₂O₃ -supported molybdena catalysts have been prepared by heating a mixture of MoO₃ and α-Fe₂O₃. XRD, XPS, LRS, TG-DTA and Mössbauer spectroscopy were used to characterize the interactions between MoO₃ and α-Fe₂O₃. The dispersion capacity of MoO₃ on the surface of α-Fe₂O₃ determined by XRD and XPS was 0.8 mmol/100m² α-Fe₂O₃ in the samples calcined at 420 . For the sample with low MoO₃ loading, LRS and FT-IR results showed that Mo⁶⁺ ions were located in the tetrahedral vacant sites on the surface of α-Fe₂O₃, signed as Mo- . The amount of Mo-II species, formed by Mo6+ ions incorporated into the octahedral vacant sites, increased with the MoO₃ loading. Based on the assumption that the (001) plane of α-Fe₂O₃ is preferentially exposed, almost all the Mo⁶⁺ ions of the dispersed molybdena species existed at the surface octahedral sites for the sample with MoO₃ loading close or beyond the dispersion capacity, and formed the Mo-II species. In this case, the capping O^2- ions linking with the incorporated Mo⁶⁺ ions formed a surface epitaxial structure, which was in good agreement with the results predicted by the incorporation model proposed previously. XRD and Mössbauer spectroscopy of the MoO₃ α-Fe₂O₃ samples calcined at different temperatures showed that the calcination temperature could strongly influence the interaction extent: ( i) at 420 , MoO₃ dispersed on the surface of α-Fe₂O₃ and formed surface Mo species; (ii ) at 500 , MoO₃ reacted with the bulk of α-Fe₂O₃ and formed Fe₂(MoO₄)₃ compound.     

Cloning,sequencing and structural analysis of a pea cDNA encoding EF-1α

A cDNA library with the capacity of 2.0 × 10⁶ was constructed using mRNA extracted, from gibberellic acid (GA)-treated G2 pea seedlings and a 1.6 kb cDNA with 100 nucleotides of 5′ non-coding region and 223 nucleotides of 3′ non-coding region was obtained by random screening. The DNA fragment contains an open reading frame of 1 344 nucleotides and encodes 447 amino acids. Sequence analysis of DNA and deduced polypeptide demonstrated that it encoded for a pea elongation factor 1-alpha (EF-1α). The functional domains of EF-1α is well conserved and EF-1α can be a good candidate for studying molecular evolution.     

Human RBCs blood group conversion from A to O using a novel α-N-acetylgalactosaminidase of high specific activity

α-N-acetylgalactosaminidase （αNAGA） can convert group A human red blood cells （RBCs） to group O. One novel αNAGA gene was cloned by PCR from Elizabethkingia meningosepticum Isolated from a domestic clinical sample. Pure recombinant αNAGA was obtained by genetic engineering and protein purification with a calculated molecule of 49.6 kD. αNAGA was selective for terminal α-N-acetylgalacto- samine residue with a high specific activity, αNAGA could completely remove A antigens of 1 U （about 100 mL） group A1 or A2 RBCs in 1 h at pH 6.8 and 25℃ with s consumption of 1.5 or 0.4 mg recombinant enzyme. Enzyme-converted group A RBCs did not agglutinate after being mixed with monoclonal snti-A or sere of groups A, B, AB and O. Other blood group antigens except ABO had no change. FCM analysis showed that A antigens and A1 antigens disappeared while H antigens increased. It indicated that αNAGA successfully converted human blood group A RBCs to universally transfusable group O RBCs without the risk of ABO-incompaUble transfusion reactions. This αNAGA was suitable for producing universal RBCs to increase clinical transfusion safety, improve the RBCs supply, and to decrease transfusion cost and support transfusion service in case of emergency.     

Molecular mechanism of abnormal aggresation of α-synuclein

The abnormal aggregation of α-synuclein （α-Syn） is thought to be closely associated with Parkinson＇s disease, but the pathogenesis is still unclear. In this review, we survey the latest development in the molecular mechanism of abnormal α-Syn aggregation, especially in the aspects of the core sequences, aggregation inhibitors, structural transformation and filament morphologies. By exploring the mechanism of α-Syn aggregation, we will have a better understanding of the disease pathogenesis, and develop strategies for preventing and treating this severe disease.     

pH effect of· OH radical induced oxidation of phosphoryl- methionine in aqueous solution

Conclusion The results of pulse radiolytical research on the · OH radical-induced oxidation of NDM in aqueous solution demonstrate that pH value has a great influence on the radiolytical mechanism of NDM. At low pH value, the product is mainly stabilization of the oxidizing sulfur centre in the three-electron-bonded cation radical NDM₂ ·⁺ [S]; with the increase of pH value, NDM₂ ·⁺ [S] gradually decays to become the reducing α-amino radical which was verified by the chemical method and whose yield was also calculated. Compared with Met₂ ·⁺ [S] produced by the · OH radical-induced oxidation in aqueous solution [1], the stability of NDM₂·⁺ [S] increases and the yield of α-amino radical decreases. This suggests that the introduction of phosphoryl group has a coordinating effect on the radioprotection of methionine to biological systems, and provides the essentially theoretical foundation for the thorough clarification of the reversible phosphorylation of proteins.     

Synthesis and relaxivity of polycarboxylic hydrazone rare earth complexes——Relaxivity of α-oxo-pentanedioic acid benzoyl hydrazone Gd-complexes

Synthesis of ligand, α-oxo-pentanedioic acid benzoyl hydrazone (H₂LPB), and its six rare earth (La, Pr, Nd, Sm, Gd and Er) complexes are reported. The composition and the properties of the complexes were characterized by element analysis, thermal analysis, UV, IR and¹H NMR spectra. Besides, relaxivity (R ₁) of Gd-complex has been determined by INVREC.Au program, using inversion recovery pulse sequences, R₁=8.05 mmol · L⁻¹ · s⁻¹. The acute toxicity of Gd-complex in animal has also been tested, and the median lethal dose (LD₅₀) is equal to (468.2±30) mg/kg.     

Second organic aerosol formation by irradiation of α-pinene-NO<Subscript>x</Subscript>-H<Subscript>2</Subscript>O in an indoor smog chamber for atmospheric chemistry and physics

Ozone（O3） and secondary organic aerosol （SOA） are considered to be the most serious secondary air pollutants of concern in most metropolitan areas, as well as for Beijing. In this study, 03 and SOA formation potential of α-pinene, the most abundant biogenic VOCs, is investigated at Tsinghua Indoor Chamber Facility. The experiments were conducted under atmospheric relevant HCs/NOx ratios in both presence and absence of ammonia sulfate seed aerosol. A Scanning Mobility Particle Sizer system （3936, TSI） and a Condensation Particle Counter （3010, TSI） were used to study the SOA formation and a gas chromatograph （GC） equipped with a DB-5 column and a flame ionization detector （FID） was used to measure α-pinene simultaneously. The results show that the presence of ammonia sulfate seed aerosol did not change the formation trend of 03, but significantly contribute to SOA formation. A strong linear relationship （r^2 = 0.90） between SOA yield enhancement （△Y＊） and surface concentration of seed aerosol （PM1, s）has been found, denoting that the PMi, s is the control factor for SOA yield enhancement. And the possible reason for the enhancement is acid-catalyzed heterogeneous reactions.