bluuebunny/crossref_metadata_2025_split huggingface dataset:
Use of Click Chemistry to Define the Substrate Specificity ofLeishmaniaβ‐1,2‐Mannosyltransferases
Authors: van der Peet Phillip , Gannon Carlie T. , Walker Ian , Dinev Zoran , Angelin Marcus , Tam Shanna , Ralton Julie E. , McConville Malcolm J. , Williams Spencer J. 
Published: July 2006

AbstractLeishmaniaspp. are human pathogens that utilize a novel β‐1,2‐mannan as their major carbohydrate reserve material. We describe a new approach that combines traditional substrate‐modification methods and “click chemistry” to assemble a library of modified substrates that were used to qualitatively define the substrate tolerance of theLeishmaniaβ‐1,2‐mannosyltransferases responsible for β‐1,2‐mannan biosynthesis. The library was assembled by using the highly selective copper(I)‐catalysed cycloaddition reaction of azides and alkynes to couple an assortment of azide‐ and alkyne‐functionalized small molecules with complementary alkyne‐ and azide‐functionalized mannose derivatives. All mannose derivatives withα‐orientated substituents on the anomeric carbon were found to act as substrates when incubated with aLeishmania mexicanaparticulate fraction containing GDP‐mannose. In contrast, 6‐substituted mannose derivatives were not substrates. Representative products formed from the library compounds were analysed by mass spectrometry, methylation linkage analysis and β‐mannosidase digestions and showed extension with up to four β‐1,2‐linked mannosyl residues. This work provides insights into the substrate specificity of this new class of glycosyltransferases that can be applied to the development of highly specific tools and inhibitors for their study.
Electrocarboxylation of Benzyl Halides through Redox Catalysis on the Preparative Scale
Authors: Scialdone Onofrio , Galia Alessandro , Silvestri Giuseppe , Amatore Christian , Thouin Laurent , Verpeaux Jean‐Noel 
Published: July 2006

AbstractThe electrocarboxylation of benzyl halides to the corresponding carboxylic acids through homogeneous charge‐transfer catalysis was investigated both theoretically and experimentally to determine the influence of the operative parameters on the yield of the process and on the catalyst consumption. Theoretical considerations, based on fast kinetics of redox catalysis, were confirmed by the electrocarboxylation of 1‐phenyl‐1‐chloroethane catalyzed by 1,3‐benzenedicarboxylic acid dimethyl ester performed at a carbon cathode under different operative conditions. We obtained high yields of the target carboxylic acid and experienced a low catalyst consumption by operating with optimized [RX]bulk/[CO2]bulk and [RX]bulk/[catalyst] ratios.
Substituent Effects on the Stereochemistry of Gas‐Phase Intracomplex Nucleophilic Substitutions
Authors: Filippi Antonello , Fraschetti Caterina , Renzi Gabriele , Roselli Graziella , Speranza Maurizio 
Published: July 2006

AbstractThe mechanism and stereochemistry of the intracomplex solvolysis of proton‐bound complexes [Y⋅⋅⋅H⋅⋅⋅M]+ between M = CH318OH and Y = 1‐arylethanol [(S)‐1‐(para‐tolyl)ethanol (1S), (S)‐1‐(para‐chlorophenyl)ethanol (2S), (S)‐1‐(meta‐α,α,α‐trifluoromethylphenyl)ethanol (3S), (S)‐1‐(para‐α,α,α‐trifluoromethylphenyl)ethanol (4S), (R)‐1‐(pentafluorophenyl)ethanol (5R), (R)‐α‐(trifluoromethyl)benzyl alcohol (6R), and (R)‐1‐phenylethanol (7R)] have been investigated in the gas phase (CH3F; 720 Torr) in the 25–140 °C temperature range. Gas‐phase solvolysis of [Y⋅⋅⋅H⋅⋅⋅M]+ (Y=2S, 3S, 4S, and 7R) leads to extensive racemization above a characteristic temperature t# (e.g. at t#>60 °C for 7R), whereas below that temperature the reaction displays a preferential retention of configuration. Predominant retention of configuration is instead observed in the intracomplex solvolysis of [Y⋅⋅⋅H⋅⋅⋅M]+ (Y=1S, 4S, 5R, and 6R) with the temperature range investigated (25 ≤ T ≤ 120 °C). These results indicate that the intracomplex solvolysis proceeds through the intermediacy of the relevant benzylic cations (Bz+), which is electrostatically coordinated to a H2O and a CH318OH molecule (a pure SN1 mechanism). The obtained gas‐phase mechanism is discussed in the light of related solution data. It is concluded that the stereochemistry of unimolecular solvolytic reactions is determined by the lifetime and the dynamics of the species involved and, if occurring in solution, by the nature and the dynamics of the solvent cage as well.
Interplay of Spin Conversion and Structural Phase Transformations: Re‐Entrant Phase Transitions in the 2‐Propanol Solvate of Tris(2‐picolylamine)iron(II) Dichloride
Authors: Törnroos Karl W. , Hostettler Marc , Chernyshov Dmitry , Vangdal Brita , Bürgi Hans‐Beat 
Published: July 2006

AbstractCrystal structures, magnetic and thermodynamic properties of the spin‐crossover compound tris(2‐picolylamine)iron(II) dichloride (with 2‐propanol solvent molecules) have been measured in the temperature range from 15 to 293 K. X‐ray diffraction, SQUID, and calorimetric experiments all showed two first‐order phase transitions with hysteresis loops, a narrow one at T1∼196 K and a broad, triangular one covering the range 153<T2<166 K. Crystal structures were analysed at fourteen temperatures in a cooling cycle and at seven temperatures in a heating cycle. They reveal a complex, temperature‐dependent ordering behaviour of both the complex cations and the alcohol molecules. A phenomenological model accounting for spin conversion, solvent ordering and coupling between the two processes describes the observed phase transitions and ordering phenomena reasonably well. Similarities and differences in the behaviour of the corresponding ethanol solvate with the same crystal architecture are discussed. It is concluded that spin‐crossover behaviour depends as much on molecular properties as it does on intermolecular interactions, both of the spin active and the spin inactive components.
Determination of the absolute configuration and solution conformation of a novel disubstituted pyrrolidine acid A by vibrational circular dichroism
Authors: Freedman Teresa B. , Cao Xiaolin , Phillips Linda M. , Cheng Peter T. W. , Dalterio Richard , Shu Yue‐Zhong , Zhang Hao , Zhao Ning , Shukla Rajesh B. , Tymiak Adrienne , Gozo Stephen K. , Nafie Laurence A. , Gougoutas Jack Z. 
Published: July 2006

AbstractCompound A, a novel disubstituted pyrrolidine acid, is a member of a new class of agents that are potentially useful for the treatment of diabetes and dyslipidemia. The absolute configuration of this compound was determined by using vibrational circular dichroism (VCD). The results are in agreement with the assignments based on both X‐ray analysis and the stereo‐selective chemical synthesis. During VCD analysis, the solution conformation for a portion of compound A in CDCl3 was also established. The compound is found to associate as an H‐bonded carboxylic acid “dimer” in CDCl3 solution, and VCD calculations on a model dimer fragment were required to establish the absolute configuration. Chirality, 2006. © 2006 Wiley‐Liss, Inc.
Semipreparative enantioseparation of Tröger base derivatives by HPLC
Authors: Sergeyev Sergey , Diederich François 
Published: July 2006

AbstractWe describe the enantioseparation of functionalized derivatives of the Tröger base by HPLC on commercially available chiral stationary phases. Cellulose‐derived Chiralcel OJ and brush‐type Whelk O1 are demonstrated to be complementary to each other in their scope. On the basis of the results obtained, the separation of selected compounds was successfully transferred onto semipreparative columns. We believe that the availability of enantiopure functionalized derivatives of the Tröger base will stimulate the further use of this interesting molecular scaffold in molecular recognition, asymmetric catalysis, and related areas of research and technology. Chirality, 2006. © 2006 Wiley‐Liss, Inc.
The Excited‐State Chemistry of Protochlorophyllide a: A Time‐Resolved Fluorescence Study
Authors: Dietzek Benjamin , Kiefer Wolfgang , Yartsev Arkady , Sundström Villy , Schellenberg Peter , Grigaravicius Paulius , Hermann Gudrun , Popp Jürgen , Schmitt Michael 
Published: July 2006

AbstractThe excited‐state processes of protochlorophyllide a, the precursor of chlorophyll a in chlorophyll biosynthesis, are studied using picosecond time‐resolved fluorescence spectroscopy. Following excitation into the Soret band, two distinct fluorescence components, with emission maxima at 640 and 647 nm, are observed. The 640 nm emitting component appears within the time resolution of the experiment and then decays with a time constant of 27 ps. In contrast, the 647 nm emitting component is built up with a 3.5 ps rise time and undergoes a subsequent decay with a time constant of 3.5 ns. The 3.5 ps rise kinetics are attributed to relaxations in the electronically excited state preceding the nanosecond fluorescence, which is ascribed to emission out of the thermally equilibrated S1 state. The 27 ps fluorescence, which appears within the experimental response of the streak camera, is suggested to originate from a second minimum on the excited‐state potential‐energy surface. The population of the secondary excited state is suggested to reflect a very fast motion out of the Franck–Condon region along a reaction coordinate different from the one connecting the Franck–Condon region with the S1 potential‐energy minimum. The 27 ps‐component is an emissive intermediate on the reactive excited‐state pathway, as its decay yields the intermediate photoproduct, which has been identified previously (J. Phys. Chem. B 2006, 110, 4399–4406). No emission of the photoproduct is observed. The results of the time‐resolved fluorescence study allow a detailed spectral characterization of the emission of the excited states in protochlorophyllide a, and the refinement of the kinetic model deduced from ultrafast absorption measurements.
Volatile Lactones — (5S,S)‐5‐Methyl‐3‐(methylalkyl)furan‐2(5H)‐ones — Identified in the Submerged Cultivation of Streptomyces Avermitilis
Authors: Řezanka Tomáš , Sigler Karel 
Published: July 2006

AbstractSix new compounds have been identified in the volatile fractions produced during the submerged cultivation of Streptomyces avermitilis. By recording the GC/MS, GC/FTIR, CD, 1H and 13C NMR data and by performing chemical degradation experiments, these compounds were determined to be (5S,S)‐5‐methyl‐3‐(methylalkyl)furan‐2(5H)‐ones. Herein, the existence of volatile lactones with an anteiso structure of the side‐chain is thus documented for the first time. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Transient response to imatinib in a chronic eosinophilic leukemia associated with ins(9;4)(q33;q12q25) and a CDK5RAP2‐PDGFRA fusion gene
Authors: Walz Christoph , Curtis Claire , Schnittger Susanne , Schultheis Beate , Metzgeroth Georgia , Schoch Claudia , Lengfelder Eva , Erben Philipp , Müller Martin C. , Haferlach Torsten , Hochhaus Andreas , Hehlmann Rüdiger , Cross Nicholas C. P. , Reiter Andreas 
Published: July 2006

AbstractChronic myeloproliferative disorders with rearrangements of the platelet‐derived growth factor receptor A (PDGFRA) gene at chromosome band 4q12 have shown excellent responses to targeted therapy with imatinib. Here we report a female patient who presented with advanced phase of a chronic eosinophilic leukemia. Cytogenetic analysis revealed an ins(9;4)(q33;q12q25) in 5 of 21 metaphases. FISH analysis with flanking BAC probes indicated that PDGFRA was disrupted. A novel mRNA in‐frame fusion between exon 13 of the CDK5 regulatory subunit associated protein 2 (CDK5RAP2) gene, a 40‐bp insert that was partially derived from an inverted sequence stretch of PDGFRA intron 9, and a truncated PDGFRA exon 12 was identified by 5′‐RACE‐PCR. CDK5RAP2 encodes a protein that is believed to be involved in centrosomal regulation. The predicted CDK5RAP2‐PDGFRA protein consists of 1,003 amino acids and retains both tyrosine kinase domains of PDGFRA and several potential dimerization domains of CDK5RAP2. Despite achieving complete cytogenetic and molecular remission on imatinib, the patient relapsed with imatinib‐resistant acute myeloid leukemia that was characterized by a normal karyotype, absence of detectable CDK5RAP2‐PDGFRA mRNA, and a newly acquired G12D NRAS mutation. © 2006 Wiley‐Liss, Inc.
Plasma concentrations of high‐dose olanzapine in a double‐blind crossover study
Authors: Kelly Deanna L. , Richardson Charles M. , Yu Yang , Conley Robert R. 
Published: July 2006

AbstractOlanzapine is structurally similar to clozapine but has not been shown at routine doses to share the superiority of clozapine to traditional antipsychotics in treatment‐resistant patients. Olanzapine, however, has been increasingly used in higher doses as clinicians attempt to find a more tolerable therapy for those refractory to conventional agents. This study examined the relationship of high‐dose olanzapine plasma concentrations to symptoms, adverse effects, smoking, and gender. Thirteen patients participated in a double blind 16‐week crossover study (8 weeks each arm) of olanzapine (50 mg/day) compared to clozapine (450 mg/day). Women had significantly higher plasma olanzapine levels than men at each time point in each arm (weeks 4, 6, and 8). At 8 weeks women had a steady‐state olanzapine level of 278 ± 62 ng/ml while men had a steady‐state level of 127 ± 47 ng/ml (p = 0.005). At week 4, olanzapine levels tended to be higher in those who had been on clozapine previously (205 ng/ml) compared to those who received olanzapine in the first arm (105 ng/ml). Cigarette intake was negatively correlated to olanzapine plasma concentrations (week 8: r = −0.86, p < 0.05). Plasma levels were significantly higher in those experiencing constipation (176 vs. 82 ng/ml; p = 0.022). Plasma levels of olanzapine were not associated with symptom response and anticholinergic effects were seen at greater frequency with higher olanzapine concentrations. In conclusion, this study reports plasma olanzapine levels at high fixed doses of olanzapine (50 mg/day) in relation to side effects, symptoms, smoking, and gender. Copyright © 2006 John Wiley & Sons, Ltd.
The legal responses of Canada and Poland to international bankruptcy and insolvency with a focus on cross‐border insolvency law
Authors: Veck Michael 
Published: July 2006

AbstractThis article discusses and compares the respective legal responses of Canada and Poland to international bankruptcy and insolvency with a focus on cross‐border insolvency law. Specifically, the issues addressed herein concern jurisdiction, recognition of foreign bankruptcy proceedings, and co‐operation with foreign courts and foreign administrators. Notwithstanding some real differences between Canadian and Polish international insolvency proceedings, both legal regimes may be compared, since both countries have adopted many of the principles contained in the UNICTRAL Model Law on Cross‐Border Insolvency. The major impetus behind the changes established by Canada in its bankruptcy and insolvency laws have been the economic realities produced by the North American Free Trade Agreement. Likewise, Poland's accession to the European Union (EU) has been a major catalyst for revising the Polish Insolvency and Restructuring Act. Part II of the said act is entirely devoted to international insolvencies. However, following Poland's adherence to the EU, those sections of the Polish Insolvency and Restructuring Act that deal with international or cross‐border insolvencies will be severely limited or constrained in scope. The article indicates that Poland, the EU and Canada are taking the necessary steps to meet the needs of debtors who would like to restructure in an international setting. Copyright © 2006 John Wiley & Sons, Ltd.
New legislative measures in South Africa aimed at combating over‐indebtedness—are the new proposals sufficient under the constitution and law in general?
Authors: Renke Stéfan , Roestoff Melanie , Bekink Bernard 
Published: July 2006

AbstractThe National Credit Bill codifies a number of fundamental rights of consumers in the credit market. It provides inter alia for a right to information to enable consumers to make informed choices and thereby contributes to one of the purposes of the proposed legislation, namely to provide mechanisms to combat over‐indebtedness. The main purpose of this research is to evaluate the proposed measures in the Bill aimed at combating over‐indebtedness and also to determine to which extent these measures comply with the general constitutional consumer protection demands. In order to achieve this, the relevant guidelines of the INSOL Consumer Debt Report and measures in other jurisdictions will also be considered. Since the South African Constitution does not directly obligate the state to enact specific credit laws and as the Bill seeks, in the spirit of the supreme law, to codify certain basic consumer rights, the new legislative initiatives are to be welcomed. It is, however, submitted that the Bill does not go far enough in achieving its particular aims and objectives and that more could be done to bring South African legislation in line with measures in other jurisdictions. Copyright © 2006 John Wiley & Sons, Ltd.
Nitroxide‐Mediated Polymerization of Methyl Methacrylate Using an SG1‐Based Alkoxyamine: How the Penultimate Effect Could Lead to Uncontrolled and Unliving Polymerization
Authors: Guillaneuf Yohann , Gigmes Didier , Marque Sylvain R. A. , Tordo Paul , Bertin Denis 
Published: July 2006

AbstractSummary: The nitroxide‐mediated polymerization (NMP) of MMA initiated with a new crowded SG1‐based alkoxyamine was performed. Contrary to the results expected after a kinetic analysis (Fischer's diagram), the polymerization of MMA at 45 °C with SG1 showed only partial control and livingness during the first 15% of conversion. Simulations using PREDICI highlighted that the kinetic rate constants currently in use had not been correctly estimated and that a strong penultimate effect drastically increased the equilibrium constant K (7 × 10−7), preventing a well‐controlled polymerization. Experimental determination of the kc value (1.4 × 104 L · mol−1 · s−1) confirmed a strong penultimate effect on the recombination reaction, whereas for the dissociation reaction this effect is lower (kd = 10−2 · s−1).Nitroxide‐mediated polymerization of MMA at 45 °C initiated with a new crowded SG1‐based alkoxyamine.magnified imageNitroxide‐mediated polymerization of MMA at 45 °C initiated with a new crowded SG1‐based alkoxyamine.
Crystallization Behavior of Poly[(butylene succinate)‐co‐adipate] Nanocomposite
Authors: Ray Suprakas Sinha , Bousmina Mosto 
Published: July 2006

AbstractSummary: The unique crystallization behavior of a poly[(butylene succinate)‐co‐adipate] (PBSA) nanocomposite is addressed. Nanocomposites have been prepared by melt blending PBSA and organically modified synthetic fluorine mica (OSFM) in a batch mixer. The structure of the nanocomposite is studied by using X‐ray diffraction and transmission electron microscopy, which reveal a coexistence of exfoliated and intercalated silicate layers homogeneously dispersed in the PBSA matrix. The non‐isothermal crystallization behavior of PBSA and the nanocomposite samples is studied by differential scanning calorimetry (DSC). Various models, namely the Avrami method, the Ozawa method, and the combined Avrami‐Ozawa method, are applied to describe the kinetics of the non‐isothermal crystallization. All analyses reveal that the incorporation of the OSFM alters the crystallization properties of PBSA but in ways unexpected from other polymer nanocomposite systems. Polarized optical microscopy is used to support this conclusion. The activation energy for the non‐isothermal crystallization of both samples is evaluated by using three different methods. The results show that the absolute value of the activation energy for the nanocomposite is higher than that of the neat polymer. This indicates the slower crystallization kinetics of the nanocomposite. The effect of incorporation of OSFM on the cold crystallization behavior of neat PBSA is also studied by both conventional and temperature‐modulated DSC.Polarized optical microscopy image of the PBSA/OSFM nanocomposite at 70 °C during non‐isothermal crystallization from the melt.magnified imagePolarized optical microscopy image of the PBSA/OSFM nanocomposite at 70 °C during non‐isothermal crystallization from the melt.
Morphology and Properties of Novel Blends Prepared from Simultaneous In Situ Polymerization and Compatibilization of Macrocyclic Carbonates and Maleated Poly(propylene)
Authors: Madbouly Samy A. , Otaigbe Joshua U. , Ougizawa Toshiaki 
Published: July 2006

AbstractSummary:Nanoscale polymer blend morphologies, with a dispersed minor phase as small as 50 nm, have been prepared via the in situ polymerization of macrocyclic carbonates in the presence of a maleic anhydride poly(propylene) (mPP). This simple, versatile, low cost strategy successfully produced a well‐defined, stable two phase nanoscale morphology with a considerable improvement in the ultimate mechanical properties and strong resistance to hydrocarbon solvents such as methylene chloride. The effect of blend composition on the rate of polymerization of the macrocyclic carbonates was studied by considering the increase in torque during the mixing process in the batch mixer. The polymerization rate decreased considerably with increasing concentration of mPP in the blend due to the formation of graft copolymer of polycarbonate‐g‐poly(propylene) (PC‐g‐PP). The viscoelastic behavior of the pure polymer components was found to play no role in controlling the blend morphology and size of the dispersed nanoscale particles. The blend morphology could be controlled by the compatibilization of the blend components, possibly via in situ formation of a graft copolymer. In addition, the blend morphology was strongly influenced by the value of the rotation speed (rpm) or shear rate encountered during the processing of the blends, i.e., the larger the rpm value, the finer the observed blend morphology. Both DSC and DMA data showed evidence of partial miscibility of the polymer blend components. In addition, the DMA data confirmed a preferential dissolution of mPP in polycarbonate (PC) instead of dissolution of PC in mPP as evidenced by the shift of theα‐relaxation process of the PC‐rich phase to lower temperatures while theα‐relaxation process of the mPP was relatively unaffected regardless of the PC composition. The percentage of mPP dissolved in PC was evaluated from the reduction in theTgvalue (obtained from DSC data) of PC in the blend using the Fox equation and was found to be consistent with the DMA data and preferential dissolution of mPP in PC.STEM photograph of mPP/PC = 10/90 blend. The sample was prepared at 225 °C and 200 rpm.magnified imageSTEM photograph of mPP/PC = 10/90 blend. The sample was prepared at 225 °C and 200 rpm.