Crystal Structure of Sar1[H79G]-GDP Which Provides Insight into the Coat-controlled GTP Hydrolysis in the Disassembly of COP Ⅱ

Sar1 is a small GTPase involved in COPⅡ vesicle transport. Previous studies showed that H79G mutation of Sar1 can lock Sar1 in its GTP-bound active conformation, stabilize coat assembly, and prevent the disassembly of COP Ⅱ vesicle coats by reducing Sec23/24 GAPstimulated hydrolysis. We show here that the replacement of His79 by glycine induces a large conformation change in switch Ⅱ and results in the lost of hydrogen bond between His79 and its associated nucleophilic water molecule that was hypothesized to reduce the GAP-stimulated hydrolysis during the COP Ⅱ assembly and disassembly. These results confirm that the switch Ⅱ conformation is important for COP Ⅱ disassembly through coat-controlled GTP hydrolysis.     

Indirect determination of cefradine with n-propyl alcohol-ammonium sulfate-water system by extraction-flotation of cuprous thiocyanate

A new method was developed for the determination of cefradine by extraction-flotation of CuSCN.The experiment indicated that in the presence of 0.20 mol/L NaOH the degradation of cefradine took place in water bath at 100℃.The thiol group(-SH)of the degradation product could reduce Cu(Ⅱ)to Cu(Ⅰ)for the formation of the emulsion CuSCN in the presence of NH_4SCN at pH 4.0.By determining the residual amount of Cu(Ⅱ)in the solution and calculating the flotation yield of Cu(Ⅱ),the indirect determination of cefradine can be obtained.This method has been applied to determine cefradine in capsules,human serum and urine samples,respectively.     

Synthesis and Crystal Structure of Binuclear Complex of Copper(Ⅱ)Chloroacetate with Acetamine

１ＩＮＴＲＯＤＵＣＴＩＯＮＣｏｐｐｅｒｃｏｍｐｌｅｘｅｓｈａｖｅａｌａｒｇｅｖａｒｉｅｔｙｏｆｓｔｅｒｉｃｓｔｒｕｃｔｕｒｅｓａｎｄｐｌａｙａｎｉｍｐｏｒｔａｎｔｒｏｌｅｉｎｃａｔａｌｙｓｉｎｇｔｈｅｅｎｚｙｍａｔｉｃａｃｔｉｖｉｔｉｅｓ，ｗｈｉｃｈ...     

Synthesis, Characterization and Crystal Structure Determination of a Thiocyanato Bridged One-dimensional Polymeric Complex of Cadmium(Ⅱ)

A new one-dimensional polymeric complex [Cd(SCN)2(H2O)]L (L = N,N?-bis(furan- 2-ylmethylene)hydrazine) has been synthesized and characterized by IR, UV spectra, TG-DTA technique and single-crystal X-ray diffraction analysis. It crystallizes in triclinic, pace group P1 with a = 5.9268(8), b = 10.8678(15), c = 13.3671(19) , α = 109.295(2), β = 95.092(2), γ = 97.8580(10)°, V = 796.70(19) 3, Z = 2, C12H10CdN4O3S2, Mr = 434.76, μ = 1.648 mm–1, Dc = 1.812 g/cm3, F(000) = 428, R = 0.0308 and wR = 0.0769. The crystal structure reveals that the structure of [Cd(SCN)2(H2O)]n features di-μ-1,3-thiocyante bridges and 1D chains. The octahedrally coordinated Cd atom is surrounded by one oxygen atom from water molecule, three S atoms and two Natoms from five di-μ-1,3 thiocyanato bridges. The Cd atoms are connected by two di-μ-1,3 thiocyanato bridges with the Cd(1)…Cd(1A) separation of 4.239(1)  and Cd(1)…Cd(1B) of 5.852(1). In addition, the one-dimensional straight chain structure is further connected by multiform intermolecular N-H…O hydrogen bonds and π…π interactions to form a three-dimensional supramolecular structure.     

Syntheses,Spectral Characterization of the Nickel(Ⅱ) Complexes of Macrocyclic Dioxotetraamine and the Effect of the Functional Pendant Arms on their Properties

１ＩＮＴＲＯＤＵＣＴＩＯＮＭａｃｒｏｃｙｃｌｉｃｄｉｏｘｏｔｅｔｒａｍｉｎｅｓｗｉｔｈｖａｒｉｏｕｓｆｕｎｃｔｉｏｎａｌｐｅｎｄａｎｔｓｈａｖｅｒｅｃｅｉｖｅｄｍｕｃｈａｔ ｔｅｎｔｉｏｎ，ｔｈｅｉｎｔｒｏｄｕｃｔｉｏｎｏｆｖａｒｉｏｕｓａｄｄｉｔｉ...     

Mass spectrometry assisted assignments of binding and cleavage sites of Zn(Ⅱ)complex towards oxidized insulin B chain

The electrospray ionization mass spectrometry investigation showed that the binding sites of [ZnL]2+, where L is 2-[bis(2-aminoethyl)aminolethanol, with oxidized insulin B chain are Phe1, His5 and Arg22, which lead to the selective cleavages of the peptide bonds at Phe1-Val2, His5-Leu6, Glu21-Arg22, and Arg22-Gly23 of oxidized insulin B chain.     

Synthesis and Crystal Structures of the α and β Forms of Bis(salicylaldoxime)copper(Ⅱ) Complexes

Modified α and β bis(salicylaldoxime)copper(Ⅱ) have been obtained by recrystallization from ethyl acetate(CCDC Nos. 212157 & 212158). The X-ray analysis reveals that the two modificated forms have the same structure with different geometric parameters. The α form crystallizes in the P2(1)/c space group and the β form in the P1 space group. Both the crystal structures consist of centrosymmetric monomeric molecules of Cu(OC6H4CNOH)2. The IR spectra are in agreement with the structural data.     

Trihydrated Complex of Tetrabenzimidazole Copper(Ⅱ) Sulfate

A Trihydrated complex of benzimidazole copper(Ⅱ) sulfate [(C7H6N2)4CuSO4]·3H2O was synthesized and structurally characterized. The crystal structure of this compound is built up of six solvated water molecules and two dissimilar copper ions identified as Cu1 and Cu2. The coordination geometry of copper(Ⅱ) is a slightly distorted square pyramid. The four equivalent tertiary nitrogen atoms of the benzimidazole ligand form an equatorial plane, while the oxygen atoms of sulfato occupy the axial site. In the solid state, the title compound forms a three dimensional network structure via hydrogen bonds. The benzimidazole, sulfato ion and H2O moieties are connected by the intermolecular hydrogen bonds. The (EPR) spectrum shows axial symmetry with g⊥=2.039 and g∥=2.285. Variable temperature magnetic susceptibility shows that there is a weak antiferromagnetic interaction between the neighboring copper(Ⅱ) ions.     

Synthesis of Nonionic Oligomeric Manganese(Ⅱ) Complexes and Investigation of Their Toxicity and Τ1-Relaxation Enhancement

Six nonionic oligomeric manganese(Ⅱ) complexes with oligomeric phosphate-polyglycol-EDTA ester ligands were synthesized and characterized. The longitudinal relaxivities of these complexes were measured. One of these complexes, which showed the highest relaxivity, was chosen to be used in the acute toxicity test and the Τ1-weighted imaging experiment. It has been found that compared to Gd-DTPA, this nonionic oligomeric Mn(Ⅱ) complex exhibits no acute toxicity, generates highly enhanced MRI signals and increases the intention time in the rat liver tissue.     

Synthesis and Electrochemical Properties of a New Tetraazamacrocyclic Complex of Silver (Ⅰ)

Themetalmacrocycliccomplexeswiththeirunusualoxidationstateshaveattractedmuchinterest.Silver(Il)andsi1ver(IlI)compoundsareusuallyunstab1eduetotheirstrongoxidation.Butsometetraazamacrocyclicligandscandirectlygivestablecom-plexesofsiIver(Il)throughdisproportionatedreactionofsilver(I).12fIere,wereportthesynthesisandeIectrochemicalbehaviorofanewsilver(Il)com-plexAgL(CIO')2(L=5,7,l2,l4-tetraethyl-5,l2-dimethyl-l,4,8,ll-tetraazacyclotetradec-4,l1-diene).Therelativeinformationaboutothersilver(1I…     

Oxygen—evloving Activity in PhotosystemⅡ Core Complex of Photosynthetic Membrane in the Presence of Native Lipid

The techniques of oxygen electrode polarography and Fourier transform infrared (FT‐IR) spectroscopy were employed to explore the involvement of digalactosyl diacylglycerol (DGDG) in functional and structural roles in the photosystem II core complex (PSIICC). It was shown that DGDG exhibited the ability to stimulate the oxygen evolution in PSIICC, which was accompanied by the changes in the structures of PSIICC proteins. The results revealed that there existed hydrogen‐bonding interactions between DGDG molecules and PSIICC proteins. It is most likely that the sites of PSIICC interaction with DGDG are in the extrinsic protein of 33 kDa.     

Simple,Selective,and Sensitive Spectrophotometric Method for Determination of Trace Amounts of Nickel(Ⅱ),Copper(Ⅱ), Cobalt(Ⅱ),and Iron(Ⅲ)with a Novel Reagent 2-Pyridine Carboxaldehyde Isonicotinyl Hydrazone

A selective and sensitive reagent of 2-pyridine carboxaldehyde isonicotinyl hydrazone(2-PYAINH)was synthesized and studied for the spectrophotometric determination of nickel,copper,cobalt,and iron in detail.At a pH value of 7.0,9.0,9.0,and 8.0,respectively,which greatly increased the selectivity;nickel,copper,cobalt, and iron reacted with 2-PYAINH to form a 1:2 yellow-orange,1:2 yellow-green,1:2 yellow and 1:1 yellow complexes,with absorption peaks at 363,352,346,and 359 nm,respectively.Under the optimal conditions,Beer's law was obeyed over the ranges of 0.01-1.4,0.01-1.5,0.01-2.7,and 0.01-5.4 mg/L,respectively.The apparent molar absorptivity and Sandell's sensitivities were 8.4×104,5.2x104,7.1×104,and 3.9×104L·mol-1.cm-1,respectively,and 0.00069,0.0012,0.00078,and 0.0014 μ g·cm-2,respectively.The detection limits were found to be 0.001,O.002,0.003,and 0.01 mg/L,respectively.The detailed study of various interfering ions to make the method more sensitive was carried out and selective and several real samples were analyzed with satisfactory results.     

Effects of Samarium on the Properties of the Anodic Pb（Ⅱ） Oxides Film Formed on Pb in Sulfuric Acid Solution

The effects of samarium on the properties of the anodic Pb(II) oxides films formed on lead at 0.9 V (vs. Hg/Hg₂SO₄) in 4.5 mol/L H₂SO₄ solution were studied using linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS) and scanning electron micrographs (SEM). The experimental results show that adding Sm to lead metal can inhibit the growth of the Pb(II) oxides film effectively, and reduce the resistance of the PbO oxides film obviously. The addition of Sm increases the porosity of the anodic film, which may cause the increase of the ionic conductance produced by the interstitial liquid among the PbO particles in the film and lead to the decrease of the resistance of the anodic film.     

Photolysis of oxygen saturated ethers in the presence of Sn(Ⅱ) or Cu(Ⅱ) salts

Photolysis of diethyl ether-oxygen charge transfer complex in the presence of Sn(Ⅱ)or Cu(Ⅱ)salts gave higher yields of the oxidation products,ethyl acetate,acetaldehyde,ethanol,ethyl formate and methanol compared with those without the salts.In addition,the photolysis of an oxygen saturated te-trahydrofuran(THF)or dibutyl ether solution gave y-butyro-lactone or butanol and butyl butyrate as major products with small amounts of undetermined compounds,respectively.Their yields were also affected by the addition of Cu(Ⅱ)or Sn(Ⅱ)salts.     

Crystal Structure of Sar1[H79G]-GDP Which Provides Insight into the Coat-controlled GTP Hydrolysis in the Disassembly of COP Ⅱ

1 INTRODUCTION The selective export of cargoes from the endore- ticulum is an evolutionarily conserved function cen- tral to cell development and proliferation. This ex- port is regulated by the Sar1 GTPase, a member of the Ras superfamily of small GTPases[1~4]. Like other Ras proteins, Sar1 functions as binary switches by cycling between inactive GDP- and active GTP- bound states[5]. The conversion of Sar1-GDP to Sar1- GTP following receptor activation is catalyzed by guanine nu…     

Synthesis and Catalytic Activity of Copper(Ⅱ) Resorcylic Acid Nanoparticles

Copper(Ⅱ) resorcylic acid(CuRes) nanoparticles were synthesized by using reactive precipitation method with resorcylic acid and blue copperas as the raw material in a rotating packed bed. The sample obtained was characterized by using X-ray diffraction( XRD), transmission electron microscopy( TEM ), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analyses (TG), and element analysis. In addition, the catalytic activity of CuRes nanoparticles on the thermal decomposition of nitrocellulose-nitroglycerine (NC-NG) was also determined via DSC.The results show that the spherical nanoparticles with a diameter of 20 nm were obtained in ethanol solution. The peak temperature of the thermal decomposition of NC-NG-CuRes decreases by 3 ℃ compared with that of normal CuRes,and the decomposition enthalpy is increased by 735 J/g, and therefore, it is reasonable to assume that CuRes nanoparticles have a better catalytic activity.     

Insertion of O-H Bond of Rh(Ⅱ)-methylene Carbene into Alcohols: A Stepwise Mechanism More Plausible than a Concerted Mechanism

The mechanisms of insertion of O-H bond of Rh( Ⅱ ) -methylene carbene into methanol and ethanol were studied by using B3LYP functional both in gas phase and in CH2Cl2. The formation of free alcoholic oxonium ylides is found to be impossible. Alcoholic oxonium ylide are formed as the intermediates before both the stepwise and the concerted transition states of insertion of O-H bond of Rh( Ⅱ ) -methylene carbene into methanol and ethanol. With regard to the mechanisms of insertion of O-H of Rh( Ⅱ ) -methylene carbene into alcohols, analysis of the energy barriers of the two mechanisms indicate that the stepwise mechanism is more plausible than the concerted mechanism.     

Studies of the Intramolecular Aromatic-ring Stacking Interactions in the Ternary Platinum(Ⅱ) Complexes

The stability constants of some ternary mixed-ligand complexes, Pt(Phen)(CA) , where Phen=1,10-phenanthroline and CA- =carboxylate, were determined by means of potentiometric pH titration in aqueous solutions(I=0.1 mol/L, KNO3; 25 ℃), and the stability of them was compared with that of the corresponding binary complexes. It was revealed that the ternary complexes containing phenylalkane carboxylates ligands(PCA-) are much more stable than those formed with formate and acetate. The results indicate that there exist the intramolecular aromatic-ring interactions between the phenanthroline ring of Phen and the phenyl moiety of ligand PCA- in the ternary mixed-ligand Pt(Phen)(PCA)- complexes. The extent of the stacking interactions, which depends on the number of methylene groups between the phenyl moieties and the coordinated phenylalkane carboxylate groups, was calculated. The best-fitted stack was obtained for the complexes with 2-phenylacetate and 3-phenylpropionate as the ligands.     

Screening and docking studies of natural phenolic inhibitors of carbonic anhydrase Ⅱ

Carbonic anhydrase Ⅱ (CAⅡ) is an important enzyme complex with Zn2+,which is involved in many physiological and pathological processes, such as calcification, glaucoma and tumorigenicity. In order to search for novel inhibitors of CAⅡ, inhibition assay of carbonic anhydrase Ⅱ was performed, by which seven natural phenolic compounds, including four phenolics (grifolin, 4-O-methyl-grifolic acid, grifolic acid, and isovanillic acid) and three flavones (eriodictyol, quercetin and puerin A), showed in-hibitory a...     

Studies of copper (Ⅱ) complexes as catalysts for the hydrolysis of DNA

Hydrolysis of DNA is an important enzymatic reaction , but it is exceedingly difficult to mimic in the laboratory because of the stability of hydrolysis of DNA. In this paper, the cleavage activity of complexes formed between Cu(Ⅱ) and four different amino acid or amino acid methyl ester on DNA is studied by gel elec-trophoresis. It is found that DNA could be cleaved by Cu(Ⅱ)-L-His and Cu(Ⅱ)-L-His methyl ester complexes and the efficiency of cleavage is largely dependent on the metal ion-to-ligand ratio. Further experiments show that the cleavage of DNA mediated by Cu(Ⅱ)-L-His complexes occurs via a hydrolytic mechanism and the active chemical species that affects DNA cleavage is proposed to be MI2H and ML2H22 .