Purification and characterization of a major glycoprotein in rat liver lysosomal membrane

A major lysosomal membrane glycoprotein (LGP107) which has an apparent molecular weight (Mr) of 107 kilodaltons (kDa) was purified from rat liver by a simple method with a yield of 1 mg/87 g wet weight of liver. The purification procedures include; preparation of tritosomal membranes of triton-filled lysosomes (tritosomes), extraction of tritosomal membranes by Lubrol PX, wheat germ agglutinin (WGA)-Sepharose affinity chromatography, and monoclonal antibody-Sepharose affinity chromatography. The quantitative immunoblot analysis indicated that LGP107 represents 6.2% of the total protein of tritosomal membranes. The isoelectric point of the purified glycoprotein was 2.7, and it moved toward neutral pH after sialidase treatment, with its molecular weight decreased by about 10 kDa. LGP107 contained 52% carbohydrates, and the carbohydrate moiety was compared of Fuc, Man, Gal, GlcNAc and sialic acid in a molar ratio of 7.2:68.2:40.6:63.0:32.3, respectively, indicating that LGP107 was highly glycosylated with N-linked complex-type olgosaccharide chains. Out of the N-linked glycans released from the glycoprotein by hydrazinolysis/N-reacetylation, about 70% was sialylated. Anion exchange and reverse-phase high performance liquid chromatography analysis on the structure of N-glycans revealed that a disialyl biantennary form is a major component in the oligosaccharide chains of LGP107.     

Use of electrophoretic techniques in determining the composition of seed storage proteins in alfalfa

Holoprotein molecular weights and polypeptide composition can be determined for complex mixtures of oligomeric proteins using two-dimensional electrophoretic techniques. The variety of two-dimensional analyses presented here is a reflection of the general usefulness of each method for the identification and characterization of the different classes of seed storage proteins in alfalfa. These techniques can be applied to studies of storage proteins in other seeds as well as non-seed storage proteins. The major seed storage proteins in alfalfa are medicagin (a legumin-like globulin), alfin (a vicilin-like globulin) and a family of lower molecular weight albumins (LMW1-3). These comprise 30%, 10%, and 20%, respectively, of the total extractable protein from cotyledons of mature seeds. Alfin is a heterogeneous oligomeric protein (Mr approximately 150,000) composed of polypeptides ranging in size from Mr 14,000 to 50,000 (alpha 1-alpha 6; 50,000, 38,000, 32,000, 20,000, 16,000 and 14,000, respectively). Medicagin is also a high molecular weight oligomeric protein, but requires high concentrations of salt for solubilisation. It is comprised of a family of individually distinct subunits, each composed of an acidic polypeptide (A1-A9; Mr 49,000 to 39,000) linked via disulphide bond(s) to a basic polypeptide (B1, B2, B3; Mr 24,000, 23,000 and 20,000, respectively). This pairing is highly specific and two families are recognizable on the basis of the B polypeptide (B3 or B1/B2). Subunits (Mr approximately 50,000-65,000) are assembled as trimers (8S) or larger oligomers (12S-15S) in mature seeds. The lower molecular weight albumins (LMW1-3) are acidic (pI less than 6), and consist of sets of disulphide-bonded polypeptides (Mr 15,000 and 11,000).     

Synthesis and Crystal Structure of a New Quinazolinone Compound 2,3-Dihydro-2-（2-hydroxyphenyl）-3-phenyl-quinazolin-4（1H）-one

A new quinazolinone compound 2,3-dihydro-2-(2-hydroxyphenyl)-3-phenylquinazolin-4(IH)-one 3 ([C2oH16O2N2]-C2H5OH, Mr = 362.42) and compound 2-(2-hydroxybenzylidene-amino)-N-phenyl-benzamide 2 (C2oH16O2N2, Mr = 316.34) were prepared from a precursor of 2-amino-N-phenyl-benzamide 1 (C13H12ON2, Mr = 212.25). Compound 3 was characterized by single-crystal X-ray diffraction analysis. The crystal belongs to orthorhombic,space group Pbca with a = 1.2889(11), b = 1.6170(14), c = 1.7729(15) nm, V= 3.695(6) nm^3, Z= 8, F(000) = 1536, Mr = 362.42, Dc = 1.303 g/cm^3, μ(MoKa) = 0.087 mm^-1, R = 0.0447 and wR= 0.0879. The crystal structure analysis indicates that the title compound has a two-dimensional network structure formed by hydrogen bonds and electrostatic interactions.     

Structure of 7, 8, 17, 18-Tetrabromo-5,10,15, 20-Tetraphenylporphinatozinc(Ⅱ)

1mrnODUCTIONRecentlywereportedthestructureof7,8,17,18--tetrabromo--5,10,15,20--tetraphenylporphinatozinc(H,TPPBr.)ill.Inordertoobservetheeffectofthefoulelectron--withdrawingbromogroupsonthestructureofametalcomplexofthisPOrphyrin,thetitlecompoundwaspreparedbyanestablishedmethod[Ziandthecrysta:wasobtained,whichissuitableforstructureanalysisbylayeringasolutioninCHCI,withpetroleum(60--90C)--piperidine.2EXPERIMENTALThetitlecomplexwassynthesizedbyreactionofH,TPPBr.andZn(CH,COO):.ZH…     

Fe-doped TiO2/SiO2 nanofibrous membranes with surface molecular imprinted modification for selective photodegradation of 4-nitrophenol

Fe-doped TiO₂/SiO₂ nanofibrous membranes with molecular imprinted modification on the surface, were fabricated and used for selective degradation of 4-nitrophenol.     

Recent studies of the interaction of rabbit dimeric IgA with its polymeric immunoglobulin receptor

Rabbit secretory components (SC) constitute a highly heteregeneous population of glycoprotein molecules that are present in secretions as free or bound forms to polymeric immunoglobulins (Ig). Two SC families are known, one of high molecular weight (⋍ 80 Kd) composed of five (perhaps six) domains related to Ig variable domains, and one of low molecular weight (⋍ 55 Kd) An account of our most recent experimental data is reviewed in this article. We have shown:

• 1.1) that both the high and low Mr SC families possess the same relative avidity for binding to dimeric IgA of the g-sublanguage;
• 2.2) that the first NH₂-terminal domain of SC derived from the high and low Mr polypeptides is necessary and sufficient for efficient non-covalent binding to dimeric IgA of the g-sublanguage;
• 3.3) that the low Mr SC polypeptide derives from the high Mr SC by the internal deletion of the entire second and third domains, suggesting that these domains are not involved in the binding reaction with polymeric Ig;
• 4.4) that the heterogeneity of rabbit secretory components is, in large part, due to the expression of several polymorphic forms (allotypes) susceptible to be recognized by specific alloantisera; the biochemical characterization of the three known SC allotypes (t61, t62 and t63) reveals that t62 and t63 are structurally very similar to each other and markedly divergent from the t61 homologue;
• 5.5) that by using non-cross-reactive alloantisera, the major immunodominant allotopes are confined within the COOH-terminal domains 3, 4 and 5 of SC;
• 6.6) that the location of the residues involved in the attachment of the carbohydrate unit within domain 1 varies according to the allotype: t61 is N-linked glycosylated at position 70, whereas about 75 % of t62 molecules are devoid of sugars; the remaining 25 % of t62 molecules are glycosylated at residue position 90; these oligosaccharide chain units are linked to asparagine residues in the acceptor site consensus sequence, Asn-X-Thr/Ser;
• 7.7) that the presence of the carbohydrate unit in domain 1 is not required for efficient binding of this domain to polymeric Ig: indeed, after enzymatic deglycosylation, domain 1 exhibits a relative binding avidity which is indistinguishable from that of the native glycosylated domain 1.

     

Dissociation channels of the 1-buten-2-yl radical and its photolytic precursor 2-bromo-1-butene

The work presented here is the first in a series of studies that use a molecular beam scattering technique to investigate the unimolecular reaction dynamics of C(4)H(7) radical isomers. Photodissociation of the halogenated precursor 2-bromo-1-butene at 193 nm under collisionless conditions produced 1-buten-2-yl radicals with a range of internal energies spanning the predicted barriers to the unimolecular reaction channels of the radical. Resolving the velocities of the stable C(4)H(7) radicals, as well as those of the products, allows for the identification of the energetic onset of each dissociation channel. The data show that radicals with at least 30.7 +/- 2 kcal/mol of internal energy underwent C-C fission to form allene + methyl, and radicals with at least 36.7 +/- 4 kcal/mol of internal energy underwent C-H fission to form H + 1-butyne and H + 1,2-butadiene; both of these observed barriers agree well with the G3//B3LYP calculations of Miller. HBr elimination from the parent molecule was observed, producing vibrationally excited 1-butyne and 1,2-butadiene. In the subsequent dissociation of these C(4)H(6) isomers, the major channel was C-C fission to form propargyl + methyl, and there is also evidence of at least one of the possible H + C(4)H(5) channels. A minor C-Br fission channel produces 1-buten-2-yl radicals in an excited electronic state and with low kinetic energy; these radicals exhibit markedly different dissociation dynamics than do the radicals produced in their ground electronic state.     

Reassessment of commercially available molecular weight standards for peptide sodium dodecyl sulfate-polyacrylamide gel electrophoresis using electroblotting and microsequencing

Myoglobin CNBr peptides, constituting the commercially available molecular weight calibration kits for sodium dodecyl sulfate-polyacrylamide gel electrophoresis, were analyzed by microsequencing after electroblotting on polyvinylidene difluoride (Immobilon) membranes. An obvious disagreement was found between peptide identification and the data provided by the manufacturers. We observed 6 peptides from Mr 2500 to 17,000 corresponding, in increasing size order, to the 3 peptides resulting from the total CNBr digestion, to 2 incompletely cleaved peptides and to the intact myoglobin. Using a corrected calibration curve, a linear relationship was established from Mr 6000 to 43,000 and a second one for shorter peptides. This method of electrophoresis and electroblotting, easily adapted for peptides, is a powerful tool for peptide identification correlated with size determination. It is especially useful for CNBr-cleaved peptides.     

助剂前体ZnSO_4浓度对苯选择加氢制环己烯Ru-Zn催化剂性能的影响

共沉淀法制备了Ru-Zn催化剂,在ZrO_2作分散剂下考察了助剂前体ZnSO_4浓度对苯选择加氢制环己烯Ru-Zn催化剂性能的影响.并用X-射线衍射(XRD)、X-射线荧光光谱(XRF)、N_2-物理吸附、透射电镜(TEM)和X-射线光电子能谱(XPS)等手段对催化剂进行了表征.结果表明,当ZnSO_4前体浓度低于0.10 mol/L时,Ru-Zn催化剂中Zn以ZnO形式存在,在加氢过程中ZnO可以与反应修饰剂ZnSO_4反应生成(Zn( OH)_2)_3(ZnSO_4)(H_2O)_3盐.继续增加ZnSO_4前体浓度,催化剂中Zn以ZnO和NaZn_4(SO_4)(Cl)(OH)_6·6H_2O盐存在,在加氢过程中ZnO和NaZn_4(SO_4)(Cl)(OH)_6·6H_2O盐可以与反应修饰剂ZnSO_4反应生成(Zn( OH)_2)_3(ZnSO_4)(H_2O)_5.(Zn( OH)_2)_3(ZnSO_4)(H_2O)_x(x=3或5)盐的Zn~(2+)可以转移金属Ru的部分电子.因此,随ZnSO_4前体浓度的增加,(Zn( OH)_2)_3(ZnSO_4)(H_2O)_x的量逐渐增加,金属Ru失电子越多,催化剂活性越低,环己烯选择性越高.0.08 mol/L ZnSO_4前体制备Ru-Zn催化剂给出了59.1%的环己烯收率,而且该催化剂具有良好的重复使用性能和稳定性.     

Two-dimensional electrophoresis of plasma proteins and high density lipoproteins during inflammation

Plasma protein and lipoprotein fractions of five patients were analyzed on day 1, 5, and 15 after severe head injury by combining three types of two-dimensional electrophoresis (2-DE) to obtain information on lipoprotein and apolipoprotein composition. On analysis under nondenaturing conditions in both dimensions on day 5, the samples show modifications of isoelectric point (pI) and molecular weight (Mr) properties of the high density lipoprotein (HDL) fraction in addition to an increase in inflammatory proteins and a return to a normal pattern on day 15. In the second type of 2-DE the samples were analyzed employing isoelectric focusing without denaturant in the first dimension, followed by sodium dodecyl sulfate (SDS) in the second dimension in order to study the protein composition of lipoprotein fractions. On day 5, a decrease of the apolipoproteins apo A-I, apo A-II, and apo C were noted, with simultaneous appearance of an unidentified protein with Mr 12,000 and pI 6.0. In the third type of 2-DE, employing urea and Nonidet P-40 in the first and SDS in the second dimension, the plasma polypeptide composition was studied. The presence of an unidentified polypeptide could be confirmed on day 5, tending to disappear thereafter. This Mr 12,000 component consists of two major spots at pI 5.7 and 6.0 and four minor ones between pI 6.0 and 8.0. These properties suggest that this protein corresponds to serum amyloid A apolipoprotein.     

Characterization of antigenic sialoglycoprotein subunits of the placental brush border membranes: comparison with liver and kidney membrane subunits by two-dimensional electrophoresis.

The sialoglycoprotein subunits of human placental brush border membranes were labeled by sequential treatment with periodate and (3H)-sodium borohydride, which trititates sialic acid, and by lactoperoxidase-catalyzed (125I) iodination of tyrosine residues. The labeled subunits were characterized with respect to their affinity for antisera raised against Triton X-100 extracts of placental brush border membranes. The immunochemically reactive components were analyzed by two-dimensional electrophoresis according to a modification of the O'Farrell technique [20] enabling the assignment of estimated Mr and pI. Of the 33 3H-labeled brush border subunits present in Triton X-100-solubilized membrane preparations, 18 subunits reacted with antiplacental brush border antisera insolubilized on CNBr-activated Sepharose or in immunoprecipitates. Fourteen of these tritiated subunits were also labeled with 125I, confirming that these are glycoproteins. The plasma membranes of normal human liver and microsomes from kidney were examined for the placental brush border glycoprotein subunits by reaction with insolubilized antiplacental brush border antisera and two-dimensional electrophoresis of the reacting tritium-labeled subunits. Comparison of the two-dimensional electrophoretic maps of the immunochemically reacting glycoproteins from liver, kidney, and placenta resulted in the identification of seven placental subunits in common with liver and kidney on the basis of antigenic cross-reactivity, Mr, and pI. Four placental glycoproteins were not found in the other tissues and are potentially specific to the placenta. Three of the placental subunits were only seen in placenta and kidney. Three of the subunits ran at the dye front and could not be assigned molecular weights. One of the subunits was poorly labeled by tritiation of sialic acid and was not considered.     

Crystal Structure of 7,3''''-Dihydroxy-4''''-methoxyisoflavone

1 INTRODUCTION Isoflavones and flavones are known to exhibit various biological activities, such as antioxidant[1～3], antiviral[4] and antibacterial[5]. The biological activi- ty of some compounds seems to depend on certain key structure and conformatio…     

THE SYNTHESIS AND STRUCTURE OF Mo_3(μ_3-O)(μ-S)_3(μ-O_2CC_6H_5)_2(dtp)_2(Py)

<正> The title compound was prepared by reaction of Mo3(μ3-O) (μ-S)3-(dtp)4 (H2O) with C6H5COONa and pyridine. C27 H35 Mo3NO9P2S7, Mr = 1091.76, monoclinic, space group P21/c, a = 15. 057(5), b = 13. 052(5), c = 21. 662(6)(?), β=105.97(2)°, V = 4093(2) (?)3, Z = 4, Dc= 1. 77gcm-3, F(000) = 2176, μ(MoKα)=13.50cm-1, final R =0. 068 for 2835 observations. The molecular configuration is new and of approximate C, symmetry, and there are two C6H5COO bridging groups in the structure. The three Mo atoms form an isosceles triangle with three sides of 2. 567(3), 2. 576(3), and 2. 649(3)(?), where the two Mo-Mo bonds bridged by C6H5COO group are much shorter than that without. Something about the reactivity of Mo clusters is discussed.     

Reaction dynamics on the formation of styrene: a crossed molecular beam study of the reaction of phenyl radicals with ethylene

The reaction dynamics of phenyl radicals (C6H5) with ethylene (C2H4) and D4-ethylene (C2D4) were investigated at two collision energies of 83.6 and 105.3 kJ mol-1 utilizing a crossed molecular beam setup. The experiments suggested that the reaction followed indirect scattering dynamics via complex formation and was initiated by an addition of the phenyl radical to the carbon-carbon double bond of the ethylene molecule forming a C6H5CH2CH2 radical intermediate. Under single collision conditions, this short-lived transient species was found to undergo unimolecular decomposition via atomic hydrogen loss through a tight exit transitions state to synthesize the styrene molecule (C6H5C2H3). Experiments with D4-ethylene verified that in the corresponding reaction with ethylene the hydrogen atom was truly emitted from the ethylene unit but not from the phenyl moiety. The overall reaction to form styrene plus atomic hydrogen from the reactants was found to be exoergic by 25 +/- 12 kJ mol(-1). This study provides solid evidence that in combustion flames the styrene molecule, a crucial precursor to form polycyclic aromatic hydrocarbons (PAHs), can be formed within a single neutral-neutral collision, a long-standing theoretical prediction which has remained to be confirmed by laboratory experiments under well-defined single collision conditions for the last 50 years.     

Sulfonated poly(styrene-co-maleic anhydride)-poly(ethylene glycol)-silica nanocomposite polyelectrolyte membranes for fuel cell applications

A method for the preparation of highly conductive and stable organic-inorganic nanocomposite polyelectrolyte membranes with controlled spacing between inorganic segment and covalently bound sulfonic acid functional groups has been established. These polyelectrolyte membranes were prepared by condensation polymerization of the silica precursor (tetraethylorthosilicate) in dimethylacetamide in the presence of poly(ethylene glycol) (PEG) of desired molecular weight, and sulfonated poly(styrene-co-maleic anhydride) was attached to the polymeric backbone by hydrogen bonding. Molecular weight of PEG has been systematically changed to control the nanostructure of the developed polymer matrix for studying the effects of molecular structure on the thermal as well as conductive properties. These polyelectrolyte membranes were extensively characterized by studying their thermo-gravimetric analysis (TGA), ion-exchange capacity (IEC), water content, conductivity, methanol permeability, and current-voltage polarization curves under direct methanol fuel cell (DMFC) operating conditions as a function of silica content and molecular weight of PEG used for membrane preparation. Moreover, from these studies and estimation of selectivity parameter among all synthesized membranes, 30% silica content and 400 Da molecular weight of PEG resulted in the best nanocomposite polyelectrolyte membranes, which exhibited performance comparable to that of the Nafion 117 membrane for DMFC applications.     

Effect of PVDF characteristics on extruded film morphology and porous membranes feasibility by stretching

Three different polyvinylidene fluoride (PVDF) resins were selected to develop porous membranes through melt extrusion and stretching. The effect of the polymer rheology on chain elongation in the melt state was studied. The possibility of generating a row‐nucleated lamellar crystallization for precursor films was investigated. The arrangement and orientation of the crystalline phase were examined by wide angle X‐ray diffraction (WAXD) and Fourier Transform Infrared Spectroscopy (FTIR). The extrusion conditions and the blend compositions were adjusted to obtain uniform precursor films with appropriate morphology. Annealing, cold and hot stretching were consequently employed to generate and enlarge the pores. It was found that a proper crystalline structure of the precursor films was strongly dependent on molecular weight of PVDF and process conditions. Blending of two PVDF resins having low and high molecular weights improved the water vapor permeability of the obtained membranes. The tensile response was monitored during the stretching process for membrane development and the results revealed a distinct behavior for the membranes having low or high permeability. The membranes with low permeability did not show any significant strain hardening during stretching whereas for highly permeable membranes, a noticeable strain hardening behavior was observed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1219–1229, 2009     

STRUCTURAL CHEMISTRY OF EIGHT-COORDINATE COMPLEXES OP MNTHANOID WITH BIDBNTATE LIGANDS IV.CRYSTAL STRUCTURES OF [C_4H_8OH] [Eu(S_2CNC_4H_8)_4]·xC_4H_8O(x=2,0)

<正> Compound [C4H3OH][Eu(S2CNC4H3)4].2C4H8O(I), Mr=953,80,monoclinic, P21/n,a = 11,332(3), b= 22,837(5), c= 15.671(2)A,β= 94.93(1)°, V= 4040.2 A3,Z= 4,Dc = 1.567 g/cm3. [C4H8OH][Bu(S2CNC4H8)4] (2),Mr=809.72, monoclinic,P 21/c,a= 12.184(2), b= 15.181(3), c= 18.334(3)A,β=98.57(1)°,V=3353,3 A3,Z = 4, Dc= 1.605 g/cm3. The Eu atom in the anions of 1 and 2 is coordinated by eight S atoms frow four S2CNC4H8 chelate groups in the form of a dodecahedron with approximate D2d symmetry.     

Optical Separation of Racemic Phenyl-alanine,and Structure of Complex Consisting of R-Phenylalanine and R-Mandelic Acid

1INTRODUCTIONTheformationofco-crystalsofadiastereo-mericmolecularcomplexisaneffectivemethodforseparatingracemicmixtureintoitsenantiomers[1,2].Asasequeltotheinvestigationonseparatingtheracemicmandelicacidbyachiralalanineinthelaboratory[3],inthepresentworkt…     

Abnormal N-heterocyclic Carbene Based Ni(II) π-allyl Complex towards Molecular Oxygen Activation

Abnormal N-heterocyclic carbene (aNHC) based Ni(II) π-allyl complexes ( 3 and 4 ) were synthesized starting from a Ni(0) precursor. These complexes were characterized by NMR spectroscopy, single-crystal X-ray crystallography ( 4 ) and elemental analysis data. The underlying mechanism for the formation of Ni(II) η³-allyl complexes from a Ni(0) precursor on treatment with a free abnormal N-heterocyclic carbene in absence of any external additive or oxidant was unraveled. Later, complex 3 was exposed to O₂ gas under ambient pressure resulting in molecular oxygen activation to form a μ-hydroxo bridged Ni(II) dimer.     

Synthesis and Characterization of the Chiral Skeleton Cluster [η~5-C_5H_4C(O)CH_2CH_2C(O)OCH_3]RuCoW(μ_3-Se)(CO)_8

1　ＩＮＴＲＯＤＵＣＴＩＯＮＴｒａｎｓｉｔｉｏｎｍｅｔａｌｃｌｕｓｔｅｒｃｏｍｐｌｅｘｅｓｈａｖｅｂｅｅｎｒｅｃｅｉｖｉｎｇｃｏｎｓｉｄｅｒａｂｌｅａｔｔｅｎｔｉｏｎｉｎｒｅｃｅｎｔ ｙｅａｒｓｌａｒｇｅｌｙｂｅｃａｕｓｅｏｆｔｈｅｉｒ ｐｏｔｅｎｔｉａｌａｐｐｌｉｃａｔｉｏｎｓｉｎｃａｔａｌｙｓｉｓａｓｗｅｌｌａｓｔｈｅｎｏｖｅｌｔｙａｎｄｖｅｒｓａｔｉｌｉｔｙｏｆｔｈｅｉｒｒｅａｃｔｉｏｎｓａｎｄｓｔｒｕｃｔｕｒｅｓ.[1～ 4] Ｏｕｒｉｎｔｅｒｅｓｔｉｎｍｅｔａｌｃｌｕｓｔｅｒｃａｔａｌｙｓｉｓｐ…