摘要:

AbstractRamachandran plots display the dihedral angles of a single protein residue. We propose a crossed torsion angle plot called SSY‐plot between two neighboring amino acids and demonstrate that a special coherence motion can exist between some very special amino acid pairs leading to spontaneous unusual structures. A 6mer was extracted from a BBA polypeptide chain which in this plot shows two diagonal domains for the Ser‐Arg pair after some induction time. Other amino acid pairs in general do not show this kind of split domain. This shows that a special pair is required for stabilizing two distinct native structures in protein folding. We suggest that the existence of these two domains corresponds to a bifurcation between two different protein structures and that the special pair is the key to producing these two structures. These two different structures are produced spontaneously without an external ag

ISSN:0009-4536    

DOI:10.1002/jccs.200600031

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractTreatment of [Cu(pcho)2(NCMe)][BF4]1(pcho = 2‐(diphenylphosphino)benzaldehyde) with aqueous H2O2in THF solvent affords [Cu2(dpb)2(THF)2(H2O)2] [BF4]22(dpb = 2‐(diphenylphosphinoxide)‐benzoate) after crystallization from diethyl ether. This reaction involves oxidation of Cu(I) to Cu(II) ion, phosphine to phosphinoxide, and benzaldehyde to benzoate species. The crystal structure of2consists of two copper(II) atoms bridged by two carboxylate moieties of the dpb ligands. The coordination about each copper(II) atom is a distorted trigonal bipy

ISSN:0009-4536    

DOI:10.1002/jccs.200600032

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractIn this work, a highly selective membrane triiodide sensor based on a new charge‐transfer complex of bis(2,4‐dimethoxybenzaldehyde)butane‐2,3‐dihydrazone with iodine (Iodide Charge Transfer complex: ICT) as membrane carrier is introduced. The influences of five different solvent mediators on sensitivity and selectivity of the proposed sensor were considered. The best performance was obtained with the membrane composition containing 30% poly (vinyl chloride), 63% DBP, 5% ICT and 2% HTAB. The electrode shows a Nernstian behavior over a very wide triiodide ion concentration range (1.0 × 10−7‐1.0 × 10−2M), and a detection limit value of 8.0 × 10−8M. The effect of pH on the potentiometric response of the sensor was also studied, and it was found that the response of the electrode is independent of the pH of the solution in the pH range of 4.0–10. The proposed sensor has a very fast response time (<12 s), and good selectivities relative to a wide variety of common inorganic and organic anions, including iodide, acetate, bromide, chloride, fluoride, nitrite, nitrate, sulfite, sulfate, cyanide and thiocyanate. In fact the selectivity behavior of the proposed triiodide ion‐selective electrode shows great improvements compared to the previously reported electrodes for triiodide ion. The proposed membrane sensor can be used for at least 6 months without any divergence in the potentials. The electrode was successfully applied as an indicator electrode in the titration of triiodid

ISSN:0009-4536    

DOI:10.1002/jccs.200600033

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThe new data for solubility of carbon dioxide are reported in mixed solvents containing (2.00 to 2.50 kmol/m3) Diisopropanolamine (DIPA), (0.86 to 1.36) kmol/m3) Piperazine (PZ), (0.86 to 1.36) kmol/m3)N‐methyldiethanolamine (MDEA) and water, keeping the amine total concentration in the aqueous solution at 3.36 kmol/m3for temperatures from (40 to 70) °C and CO2partial pressures in the range of (30 to 5000) kPa. Experimental solubility results were represented by the mole ratio of CO2per total amine in the liquid mixture. Results show that at a given partial pressure of CO2the solubility of CO2in the DIPA solutions is lower than solubility in MDEA or PZ solutions and the CO2loading increased with decreasing temperature and increasing CO2partial pressu

ISSN:0009-4536    

DOI:10.1002/jccs.200600034

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractBlack solid precursors obtained from reactions between MCl5(M = Nb, Ta) and alkyllithiums, n‐butyllithium (nBuLi) and ethyllithium (EtLi), in tetrahydrofuran (THF) were heat treated under vacuum at 673–973 K to form nano‐sized particles (20–100 nm in diameter) of lithium niobate (LiNbO3) and lithium tantalate (LiTaO3). Stoichiometry of the reactants is critical and affects the phases of the products. Based on the volatile byproducts detected, a reaction pathway involving the activation of THF by alkyllithiums is proposed to be important for the formation of LiNbO3and LiTaO3pre

ISSN:0009-4536    

DOI:10.1002/jccs.200600035

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractA binuclear samarium(III) complex with benzoic acid and 1,10‐phenanthroline, [Sm(BA)3phen]2was synthesized and characterized by elemental analysis, UV, IR and TG‐DTG techniques. The structure of the title complex was established by single crystal X‐ray diffraction. The crystal is triclinic, space group P1 witha= 10.8216(11) Å,b= 11.9129(13) Å,c= 12.425(2) Å, α = 105.007(2)°, β = 93.652(2)°, γ = 113.2630(10)°,Z= 1,Dc= 1.650 mg·m−3,F(000) = 690. The carboxylate groups are bonded to the samarium ion in three modes: bidentate chelating, bidentate bridging, and tridentate chelating‐bridging. Each Sm3+ion is coordinated to one bidentate chelating carboxylate group, two bidentate bridging and two tridentate chelating‐bridging carboxylate groups, as well as one 1,10‐phenanthroline molecule, forming a nine‐coordinate metal ion. Based on thermal analysis, the thermal decomposition process of [Sm(B

ISSN:0009-4536    

DOI:10.1002/jccs.200600036

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThe reaction ofN,N′‐di(2‐pyridyl)formamidine (HDpyF) with MnCl2‐4H2O afforded the complex MnCl2(HDpyF), which was characterized by X‐ray crystallography. The HDpyF ligand chelates to the Mn(II) center through the first and the third nitrogen atoms to form a six‐membered ring, leaving the second and the fourth nitrogen atoms uncoordinated. The HDpyF ligand is crystallographically disordered such that two different molecules can be solved. The neutral HDpyF ligand adopts the news‐cis‐syn‐s

ISSN:0009-4536    

DOI:10.1002/jccs.200600037

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThe reaction of Zn(NO3)2‐6H2O, NH4SCN and bpp (bpp = 1,3‐bis(4‐pyridyl)propane) in CH3OH afforded the complex [Zn(NCS)2(bpp)]n,1, while the reaction of Zn(ClO4)2‐6H2O and bpp in CH3OH afforded the complex [Zn(ClO4)2(bpp)2]n,2. Both complexes have been characterized by spectroscopic methods and their structures have been determined by X‐ray crystallography. Crystal data for1: Orthorhombic, space group P21212, a= 12.857(6), b = 14.822(7), c = 4.820(2) Å, β = 90°, V = 918.5(8) Å3, Z = 2 with final residuals R1 = 0.0747 and wR2 = 0.1657. Crystal data for2: Tetragonal, space group I4/mcm, a = 11.612(1), b = 11.612(1), c = 23.247(9) Å, β = 90°, V = 3135(1) Å3, Z = 4 with final residuals R1 = 0.0523 and wR2 = 0.1064. The coordination polymers display a variety of structural architectures, ranging from zigzag chains (1) and one‐dimensional channel‐type architectures (2). The effects of the orientation of the nitrogen atom in the pyridine rings on the resultant str

ISSN:0009-4536    

DOI:10.1002/jccs.200600038

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractThe complex characteristics and mechanisms of aluminum pitting corrosion in a solar heating system were studied by the chemical immersion method and electrochemical techniques as well as fractal theory. The results showed that pitting corrosion of Al occurred in a tap water environment due to the local enrichment of Cl−ions. The higher the Cl−ions concentration, the more negative the critical pitting potential (Eb) of Al. A linear relationship betweenEband the logarithm of Cl−ions concentration was observed. The pitting corrosion mechanism of Al in neutral water was explained in terms of complexation corrosion theory. The corrosion surface images of aluminum immersed in tap water were captured and analyzed by image processing technique and box‐dimension method. The fractal characteristics of pit distribution, described by fractal dimension, have been identified. The fractal dimension of the pit distribution increased with the increase of immersion time and had the same trend as that of the weight loss. Fractal dimension can, thus, be used as an important parameter for quantitative evaluation of pitting corrosion of a

ISSN:0009-4536    

DOI:10.1002/jccs.200600039

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY

摘要:

AbstractTitania thin film was deposited successfully on polyacrylonitrile (PAN) fiber by the sol‐gel process with the assistance of tetraethyl silicate (TEOS) at low temperature. It was found that the densification and crystallization of the film was a result of the post‐treatment in boiling water because of the hydrolysis of the Si‐O‐Ti bonds and dissolution of the silica component formed in the film. XRD patterns revealed the existence of anatase phase in the continuous titania layer. The product, titania coated polyacrylonitrile fiber (TiO2/PAN), showed a high photocatalytic property and good repetition on the photodegradation of methylene blue (MB). The proposed method is expected to be used for the preparation of novel photo‐catalysts based on thermally sensitive s

ISSN:0009-4536    

DOI:10.1002/jccs.200600040

出版商:WILEY‐VCH Verlag    

年代:2006

数据来源: WILEY