bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conformational Flexibility and Dynamics of Two (1→6)‐Linked Disaccharides Related to an Oligosaccharide Epitope Expressed on Malignant Tumour Cells
Authors: Olsson Ulrika , Säwén Elin , Stenutz Roland , Widmalm Göran 
Published: July 2009

AbstractThe conformational flexibility and dynamics of two (1→6)‐linked disaccharides that are related to the action of the glycosyl transferase GnT‐V have been investigated. NMR NOE and T‐ROE spectroscopy experiments, conformation‐dependent coupling constants and molecular dynamics (MD) simulations were used in the analyses. To facilitate these studies, the compounds were synthesised as α‐d‐[6‐13C]‐Manp‐OMe derivatives, which reduced the 1H NMR spectral overlap and facilitated the determination of two‐ and three‐bond 1H,1H, 1H,13C and 13C,13C‐coupling constants. The population distribution for the glycosidic ω torsion angle in α‐d‐Manp‐(1→6)‐α‐d‐Manp‐OMe for gt/gg/tg was equal to 45:50:5, whereas in α‐d‐Manp‐OMe it was determined to be 56:36:8. The dynamic model that was generated for β‐d‐GlcpNAc‐(1→6)‐α‐d‐Manp‐OMe by MD simulations employing the PARM22/SU01 CHARMM‐based force field was in very good agreement with experimental observations. β‐d‐GlcpNAc‐(1→6)‐α‐d‐Manp‐OMe is described by an equilibrium of populated states in which the ϕ torsion angle has the exo‐anomeric conformation, the ψ torsion angle an extended antiperiplanar conformation and the ω torsion angle a distribution of populations predominantly between the gauche–trans and the gauche–gauche conformational states (i.e., gt/gg/tg) is equal to 60:35:5, respectively. The use of site‐specific 13C labelling in these disaccharides leads to increased spectral dispersion, thereby making NMR spectroscopy based conformational analysis possible that otherwise might be difficult to attain.
Ferrocene–β‐Cyclodextrin Conjugates: Synthesis, Supramolecular Behavior, and Use as Electrochemical Sensors
Authors: Casas‐Solvas Juan M. , Ortiz‐Salmerón Emilia , Fernández Ignacio , García‐Fuentes Luís , Santoyo‐González Francisco , Vargas‐Berenguel Antonio 
Published: July 2009

AbstractFerrocene with a β‐cyclodextrin unit bound to one or both cyclopentadienyl rings through the secondary face were conveniently synthesized by regiospecific copper(I)‐catalyzed cycloaddition of 2‐O‐propargyl‐β‐cyclodextrin to azidomethyl or bis(azidomethyl)ferrocene. The supramolecular behavior of the synthesized conjugates in both the absence and presence of bile salts (sodium cholate, deoxycholate, and chenodeoxycholate) was studied by using electrochemical methods (cyclic and differential pulse voltammetry), isothermal titration calorimetry, and NMR spectroscopy (PGSE, CPMG, and 2D‐ROESY). These techniques allowed the determination of stability constants, mode of inclusion, and diffusion coefficients for complexes formed with the neutral and, in some cases, the oxidized states of the ferrocenyl conjugates. It was found that the ferrocenyl conjugate with one β‐cyclodextrin unit forms a redox‐controllable head‐to‐head homodimer in aqueous solution. The ferrocene–bis(β‐cyclodextrin) conjugate is present in two distinguishable forms in aqueous solution, each one having a different half‐wave oxidation potential for the oxidation of the ferrocene. By contrast, only one distinguishable form for the oxidized state of the ferrocene–β‐cyclodextrin conjugate is detectable. The redox‐sensing abilities of the synthesized conjugates towards the bile salts were evaluated based on the observed guest‐induced changes in both the half‐wave potential and the current peak intensity of the electroactive moiety.
Perfluorophenyl–Phenyl Interactions in the Crystallization and Topochemical Polymerization of Triacetylene Monomers
Authors: Xu Rui , Schweizer W. Bernd , Frauenrath Holger 
Published: July 2009

AbstractA series of symmetrically and unsymmetrically substituted octa‐2,4,6‐triyne‐1,8‐diol derivatives with benzoyl, 4‐dodecyloxybenzoyl, as well as perfluorobenzoyl substituents were prepared and investigated with respect to their crystal structures and topochemical polymerizability. Single‐crystal structures for several of these triacetylene monomers have been obtained and proved that the perfluorophenyl–phenyl interactions played a decisive role in the molecular packing. As a consequence of the geometric requirements imposed by the perfluorophenyl–phenyl interactions, packing parameters appropriate for a topochemical triacetylene polymerization in the sense of either a 1,6‐ or a 1,4‐polyaddition along different crystallographic axes were observed in two cases, and UV irradiation led to successful polymerization. Raman as well as solid‐state 13C NMR spectra of the obtained polymers revealed that the polymerization had predominantly proceeded in the form of a 1,4‐polyaddition.
Self‐Assembly in Helical Columnar Mesophases and Luminescence of Chiral 1H‐Pyrazoles
Authors: Beltrán Eduardo , Cavero Emma , Barberá Joaquín , Serrano José Luis , Elduque Anabel , Giménez Raquel 
Published: July 2009

AbstractChiral polycatenar 1H‐pyrazoles self‐assemble to form columnar mesophases that are stable at room temperature. X‐ray diffraction and CD studies in the mesophase indicate a supramolecular helical organization consisting of stacked H‐bonded dimers. The liquid‐crystalline compounds reported are 3,5‐bis(dialkoxyphenyl)‐1H‐pyrazoles that incorporate two or four dihydrocitronellyl chiral tails. It can be observed that the grafting of these branched chiral substituents onto the 3,5‐diphenyl‐1H‐pyrazole core has a beneficial role in inducing mesomorphism, because isomeric linear‐chain compounds are not liquid crystalline; this is not the usual scheme of behavior. Furthermore, the molecular chirality is transferred to the columnar mesophase, because preferential helical arrangements are observed. Films of the compounds are luminescent at room temperature and constitute an example of the self‐organization of nondiscoid units into columnar liquid‐crystalline assemblies in which the functional molecular unit transfers its properties to a hierarchically built superstructure.
Structural Analyses of N‐Acetylated 4‐(Dimethylamino)pyridine (DMAP) Salts
Authors: Lutz Volker , Glatthaar Jörg , Würtele Christian , Serafin Michael , Hausmann Heike , Schreiner Peter R. 
Published: July 2009

AbstractWe have studied the formation of several N‐acetyl‐4‐(dimethylamino)pyridine (DMAP) salts (with Cl−, CH3COO−, and CF3COO− counterions), which are considered to be the catalytically active species in DMAP‐catalyzed acetylation reactions of alcohols. Combined crystal structure analyses, variable temperature matrix IR and NMR spectroscopy as well as computational techniques at the UAHF‐PCM‐B3LYP/6‐311+G(d,p)//B3LYP/6‐31G(d) level were utilized to examine the structures and dynamics of salt formation. We found clear evidence for the formation of tight ion pairs that are stabilized by dynamic hydrogen‐bonding interactions. In nonpolar solvents, the nucleophilicity of acetate in its N‐acetyl‐DMAP salt only allows a steady‐state concentration smaller 1 % at room temperature. Thus, we propose additional hydrogen‐bonding interactions with alcohols to be the key stabilization factor in subsequent acetylations.
Low‐tmperature Heat Capacities and Standard Molar Enthalpy of Formation of 4‐Nitrobenzyl Alcohol
Authors: MENG Qingfen , TAN Zhicheng , WANG Xiaohuan , DONG Yaping , LI Wu , SHI Quan 
Published: July 2009

AbstractLow‐temperature heat capacities of 4‐nitrobenzyl alcohol4‐NBAhave been measured by a high precision automated adiabatic calorimeter over the temperature range from 78 to 396 K. The melting temperature, the molar enthalpy and entropy of the phase transition were determined to be (336.426±0.088) K, (20.97±0.13) kJ·mol−1 and (57.24±0.36) J·K−1·mol−1, respectively. The thermodynamic functions [HT−H298.15 K] and [ST−S298.15 K] were calculated in the range from 80 to 400 K at the interval of 5 K. The constant‐volume energy and standard molar enthalpy of combustion have been determined, ΔcU(C7H7NO3, s) =− (3549.11±1.47) kJ·mol−1 and ΔcHm0 (C7H7NO3, s) =− (3548.49±1.47) kJ·mol−1, by means of a precision oxygen‐bomb combustion calorimeter at T=298.15 K. The standard molar enthalpy of formation has been derived, ΔfHm0 (C7H7NO3, s) =− (206.49±2.52) kJ·mol−1, from the standard molar enthalpy of combustion in combination with other auxiliary thermodynamic quantities through a Hess thermochemical cycle.
Reduction Kinetics of Thionine in Aerobic Condition with D‐Galactose
Authors: AHMED Khalid , UDDIN Fahim , AZMAT Rafia 
Published: July 2009

AbstractReduction kinetics of thionine (Th) with D‐galactose (RH) was observed on a UV/Visible 1601 Shimadzu spectrophotometer at λmax 599 nm. The results showed that the initially slow reduction kinetics got enhanced and proceeded to completion within a few minutes. A pseudo first order kinetics was observed when influence of different parameters like concentration of dye and reductant, ionic strength and temperature was investigated. A significant shift in wave length from 599 to 517 nm was observed at alkaline pH whereas addition of a small amount of acid caused a shift in equilibrium. This resulted in the generation of oxidized form of thionine which was pragmatic in the presence of atmospheric oxygen. Change in ionic strength at elevated temperature lied to decrease in the rate constant. Thermodynamics activation parameters like Ea reflects a high amount of energy required for reduction of Th with RH whereas entropy of activation (ΔS⊖) and free energy of activation (ΔG⊖) show the highly solvated states of transient complex which was less disorderly arranged than the oxidized form of dye. A mechanism consistent with above findings has been discussed in the relevant section of paper.
Photo Decoloration of Methylene Blue with Ribose under Optimum Conditions by Visible Radiation
Authors: AZMAT Rafia , UDDIN Fahim 
Published: July 2009

Abstract Photo decoloration of the methylene blue (MB) with reducing sugar, ribose (RH), was investigated on an especially designed optical processor using monochromatic radiation of 661 nm through a red filter. The dye molecule gets excited into triplet transient species (MBT) during flushing with lifetime of 10.1 µs into acetate buffered aqueous alcoholic medium, which later on reduces to protonated leuco dye (MBH). Photolysis of the aqueous alcholic medium generated highly reactive oxygen radical (O−·) with the production of 2e−, which led to probable oxidation of the ribose into respective acid while hydrogen abstraction and 2e− reduced the dye (MB) into MBH by following reaction
MBr++RCHO→MBH+RCOOH. Influences of different operational parameters suggest the imperative role of acidity, reductant and temperature where positive relations with quantum yield (π) were established under the optimum conditions while elevated concentration of dye resulted in the decrease in the absorption of number of photon consequently, and no change in the π was observed. A highly solvated transient complex was reported in the reduction of MB and RH through thermodynamics activation parameters. A mechanism of MBT formation and its reduction into MBH has been discussed.
Novel Synthesis of β‐FeOOH Nanofluid and Determination of Its Heat Capacity by an Adiabatic Calorimeter
Authors: NAN Zhaodong , ZHANG Pingping , YU Aijun , WEI Chengzhen , SHI Quan , TAN Zhicheng 
Published: July 2009

AbstractA novel and facile method for preparation of stable nanofluid is introduced, in which FeCl3·6H2O and urea were used as reactants without any surfactants. The obtained solid sample was proved to be β‐FeOOH by XRD technology and spindle‐shaped by TEM technology. The coexisting NH3 molecules may be the main reason for the stable nanofluid. The weak bonding between nitrogen and iron atoms would be formed. The investigation on the excess heat capacity of the obtained nanofluid sustains this opinion. The heat capacities of the obtained β‐FeOOH particles and the nanofluid were determined by an adiabatic calorimeter. And these obtained results will help the applications of β‐FeOOH and the nanofluid to industry, and the establishment of the model of thermal conductivity of nanofluid. The thermodynamic properties of the obtained β‐FeOOH particles and the nanofluid were calculated based on the obtained functions of heat capacity with respective to thermodynamic temperature and the relationships between the thermodynamic properties.
Preparation and Electrical Property of Ba1.03Ce0.8Ho0.2O3−α Solid Electrolyte
Authors: WANG Maoyuan , QIU Ligan , SUN Yufeng 
Published: July 2009

Abstract Ba1.03Ce0.8Ho0.2O3−α solid electrolyte with nonstoichiometric composition was prepared by high temperature solid‐state reaction. Phase composition, surface and fracture morphologies of the material were characterized by using XRD and SEM, respectively. Ionic transport number and conductivity of the material were measured by gas concentration cell and ac impedance spectroscopy methods in the temperature range of 600–1000°C in dry air, wet air and wet hydrogen, respectively. Ionic conduction was researched and compared with those of BaCe0.8Ho0.2O3−α and Ba0.97Ce0.8Ho0.2O3−α. The results indicate that Ba1.03Ce0.8Ho0.2O3−α is a single‐phase perovskite‐type orthorhombic system. In the temperature range of 600–1000°C, it is a mixed conductor of oxide ion and electron hole with the oxide ionic transport number of 0.10–0.36 in dry air atmosphere, a mixed conductor of proton, oxide ion and electronic hole with the protonic transport number of 0.11–0.01 and the oxide ionic transport number of 0.34–0.30 in wet air atmosphere, and a pure protonic conductor with the protonic transport number of 1 in wet hydrogen atmosphere. Ba1.03Ce0.8Ho0.2O3−α has the highest conductivities (3.92×10−2 S·cm−1 in dry air, 3.46×10−2 S·cm−1 in wet air, 2.10×10−2 S·cm−1 in wet hydrogen, at 1000°C) among the three materials, and the ionic conduction is superior to that of BaCe0.8Ho0.2O3−α and Ba0.97Ce0.8Ho0.2O3−α under the experimental conditions.
Theoretical Study on Reaction of Furan Anion with N2O in Gas Phase
Authors: LIANG Junxi , GENG Zhiyuan , WANG Yongcheng 
Published: July 2009

AbstractThe mechanism for the ion‐molecule reaction of furan anion with nitrous oxide has been explored theoretically using the QCISD and MP2 levels of theory with the same 6‐31++G(d,p) basis set. As a result, our theoretical investigations strongly suggest that the main pathways, whose energies of all stationary points lie below that of the original reactants (furan anion+N2O), can be expressed as pathways 1 and 2 of the Channel 1, which are two reciprocally competitive pathways. The primary products were C4H3NO−+NO, synchronously, a trace amount of C4H3O2−+N2 should also be monitored in the experiment. Theoretical calculated results are consistent with the experimental observation. Furthermore, the minor pathways were also explained in a nutshell. All the reactive pathways, regardless of the main or minor ones, are strongly exothermic processes.
Synthesis, Characterization and Biological Activity of an Intramolecular Stacking Zinc(II) Complex
Authors: GAO Enjun , LIU Lei , ZHU Mingchang , WU Qiong 
Published: July 2009

AbstractThe synthesis, crystallographic analysis and spectroscopic study of a zinc(II) complex [Zn(bipy)(pmal)(H2O)]· 2H2O (bipy=2,2′‐bipyridine, pmal=phenylmalonic acid) were carried out. The complex has been investigated by the methods of X‐ray crystallography, elemental analysis and IR spectra. The binding ability of the Zn(II) complex to calf thymus (CT‐DNA) was characterized by measuring the effects on the UV spectroscopy and fluorescence spectra of DNA. The agarose gel electrophoresis experimental results suggest that the ligand planarity of complex has a significant effect on cleaving the pBR322 plasmid DNA.
Activation Function of Chloroperoxidase in the Presence of Metal Ions at Elevated Temperature from 25 to 55°C
Authors: GAO Qiang , JIANG Yucheng , GAO Xiaoqin , HU Mancheng , LI Shuni , ZHAI Quanguo 
Published: July 2009

Abstract The investigation and comparison of chlorination activity of chloroperoxidase (CPO) from Caldariomyces fumago in metal ion solutions to those in pure buffer indicated that CPO could be effectively activated by some alkaline‐earth metals and transition metals. The obtained maximum relative activity of CPO was 1.33 time at 75 µmol·L−1 Ca2+, 1.37 time at 90 µmol·L−1 Mg2+, 1.34 time at 90 µmol·L−1 Ni2+, and 1.27 time at 105 µmol·L−1 Co2+ at 25°C. Moreover, the CPO stability against temperature was improved in the presence of the above metal ions. At 55°C, CPO could retain only about 40% of activity whereas 75% and 81% of activity were maintained in Mg2+ and Ca2+ media, respectively. It was suggested that the metal ions bind to the acid‐base catalytic groups Glu183, His105 and Asp106 around the active site of CPO, and activate CPO by both an enrichment of substrate concentration and the conformational change of CPO, which are favorable to the substrate access. The analysis of kinetic parameters indicated that the activation was mainly due to an increase in kcat values. The affinity and specificity of CPO to substrates were also improved in these metal ion media. The results in this work are promising in view of industrial applications of this versatile biological catalyst.
Synthesis, Structure, Magnetism and Electrochemical Properties of Linear Pentanuclear Complex: Ni5(µ‐dmpzda)4(NCS)2
Authors: YIN Caixia , HUO Fangjun , WANG Wenzhen , ISMAYILOY Rayyat‐H , LEE Genehsiang , YEH Chenyu , PENG Shieming , YANG Pin 
Published: July 2009

Abstract The synthesis, crystal structure, electrochemical and magnetic properties of a type of pyridine‐modulated linear pentanuclear complex, [Ni5(µ‐dmpzda)4(NCS)2] [dmpzda‐H2=N,N′‐di(4‐methyl pyridin‐2‐yl)pyrazine‐2,6‐diamine], were studied. The complex involves a Ni5 linear chain unit with all of the Ni‐Ni‐Ni being nearly 180°, terminated by the two axial ligands. This pentanuclear linear metal chain is helically wrapped by four syn‐syn‐syn‐syn type dmpzda ligands. There are two types of Ni–Ni distances existing in the complex. The terminal Ni–Ni distances bonded with the axial ligand are longer (2.3821 Å) affected by the axial ligands. The inner Ni–Ni distances are very short and remain constant (2.2959 Å). Two terminal Ni(II) ions bonded with the axial ligands are in a square‐pyramidal (NiN4NCS) environment and exhibit long Ni–N bonds (2.103 Å), which are consistent with a high‐spin Ni(II) configuration. The inner three Ni(II) ions display short Ni–N (1.886–1.906 Å) bond distances, which are consistent with a squareplanar (NiN4), diamagnetic arrangement of a low‐spin Ni(II) configuration. This compound exhibits similar [Ni5(µ‐tpda)4(NCS)2] magnetic behavior, indicating an antiferromagnetic interaction of two terminal high‐spin Ni(II) ions in these complexes.
Synthesis, Characterization and Antimicrobial Activity of Potassium Hydro(benzoyl)(phthalyl)borate and Its Cobalt(II), Nickel(II), and Copper(II) Complexes
Authors: SHARMA Guruaribam Shashikumar , SHEIKH Rayees Ahmad , SHREAZ Sheikh , HASHMI Athar Adil , KHAN Luqman Ahmad 
Published: July 2009

AbstractA new organoborate ligand, hydro(benzoyl)(phthalyl)borate has been synthesized as its potassium salt (KL) and treatment of KL with one equivalent of MCl2·6H2O gave complexes ML(H2O)x·Cl [x=2, M=Co(II), Ni(II); x=1, M=Cu(II)]. All compounds were characterized by elemental analysis, FTIR, 1H NMR, ESI MS, UV‐Vis techniques, conductivity and magnetic data measurements. Spectroscopic results suggest a square planar geometry in the Cu(II) complex, while the Co(II) and Ni(II) complexes possess an octahedral geometry. Antibacterial activities (in vitro) of the ligand and its metal complexes were studied against two Gram positive (B. subtillis and B. magterium) and two Gram negative bacteria (E. Coli and S. boydi) at a single concentration (75 µg/mL) by using the Disc diffusion method. Antifungal activities (in vitro) were also checked for the compounds by using the same method against Candida albicans 10261, Penicillium sp. and Asperjillius niger., at a single concentration (50 µg/mL). The results showed that all the metal complexes, specially the nickel(II) complex, have higher antibacterial and antifungal activities than the corresponding potassium salt.
Preparation, Characterization and Properties of Ag(I) Coordination Polymer [Ag2(bpp)2(H2O)]·pydc·7H2O
Authors: GUO Chunyan , WEN Guilin , WANG Yaoyu , FU Aiyun , LERMONTOVA Elmira Kh , SHI Qizhen 
Published: July 2009

AbstractA new coordination polymer, [Ag2(bpp)2(H2O)]·pydc·7H2O (1), derived from the ligand pyridine‐3,5‐dicarboxylic acid (H2pydc), has been obtained through a hydrothermal technique [bpp=1,3‐bis(4‐pyridyl)propane]. Its single crystal structure has been determined by X‐ray crystallography. A 2D sheet containing (H2O)12 water units was formed. Interestingly, each pydc dianion bridged two (H2O)12 units and two free water molecules in the construction of 2D hydrogen‐bonding sheets. Additionally, fluorescent properties, TG analysis, and PXRD for complex 1 were also measured and discussed.
Synthesis, Crystal Structure and Bioactivities of a Novel Propeller Shaped Manganese Complex with the Ligand N′‐Benzylidenesalicylhydrazide
Authors: LI Bo , SUN Xuzhuo , CHENG Gongzhen , JI Zhenping 
Published: July 2009

AbstractA new propeller shaped mononuclear manganese(III) complex of the general formula: [MnL3(H2O)], where HL is N′‐benzylidenesalicylhydrazide, was synthesized and characterized. The crystal structure of the title compound was characterized by X‐ray single crystal diffractometry, which belongs to a triclinic system with space group P‐1, cell dimensions of a=11.6411 Å, b=12.728 Å, c=16.346 Å, α=110.357°, β=96.555°, γ=108.996°, V=2075.2 Å3, Z=2 and Dcalc=1.265 g/cm3. In this complex, the metal ion is in an octahedral coordination environment, enforcing the stereochemistry of the ligands as a propeller configuration. Antibacterial screening data indicate that the complex has stronger antibacterial activity against the tested microorganisms than the ligand.
Improving the Robustness and Stability of Partial Least Squares Regression for Near‐infrared Spectral Analysis
Authors: SHAO Xueguang , CHEN Da , XU Heng , LIU Zhichao , CAI Wensheng 
Published: July 2009

AbstractPartial least‐squares (PLS) regression has been presented as a powerful tool for spectral quantitative measurement. However, the improvement of the robustness and stability of PLS models is still needed, because it is difficult to build a stable model when complex samples are analyzed or outliers are contained in the calibration data set. To achieve the purpose, a robust ensemble PLS technique based on probability resampling was proposed, which is named RE‐PLS. In the proposed method, a probability is firstly obtained for each calibration sample from its residual in a robust regression. Then, multiple PLS models are constructed based on probability resampling. At last, the multiple PLS models are used to predict unknown samples by taking the average of the predictions from the multiple models as final prediction result. To validate the effectiveness and universality of the proposed method, it was applied to two different sets of NIR spectra. The results show that RE‐PLS can not only effectively avoid the interference of outliers but also enhance the precision of prediction and the stability of PLS regression. Thus, it may provide a useful tool for multivariate calibration with multiple outliers.