bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis, characterization and fluorescent properties of cerium(III) glutathione complex
Authors: Han Guo‐Cheng , Liu You‐Nian 
Published: August 2009

AbstractThe cerium (III) glutathione complex was synthesized by the redox reaction of cerium (IV) with glutathione reduced (GSH) in aqueous solution. The Job‐plots indicate an ML (L = GSSG) stoichiometry of the complex. The fluorescent properties of the compound were investigated. The as‐prepared complex showed the characteristic maximum emission spectra of Ce(III) at 350 nm (λex = 255 nm). The fluorescence results show that the Ce(IV) ions are first reduced to Ce(III), and then form Ce(III) complex after reacting with GSH. The complex was characterized by element analysis and FT‐IR spectra; the stability of the complex was analyzed by cyclic voltammeters and DSC‐TG as well. Finally, Ce(IV) was successfully employed to determine the concentrations of GSH in the presence of GSSG, in which the fluorescence intensities are proportional to the concentrations of GSH in the range of 1–100 nM with the detection limit of 0.05 nM of GSH, without interference from the presence of GSSG. Copyright © 2009 John Wiley & Sons, Ltd.
Conformational stability of the full‐atom hexameric model of the ClpB chaperone from Escherichia coli
Authors: Ziętkiewicz Szymon , Ślusarz Magdalena J. , Ślusarz Rafał , Liberek Krzysztof , Rodziewicz‐Motowidło Sylwia 
Published: August 2009

AbstractThe Escherichia coli heat shock protein ClpB, a member of the Hsp100 family, plays a crucial role in cellular thermotolerance. In co‐operation with the Hsp70 chaperone system, it is able to solubilize proteins aggregated by heat shock conditions and refold them into the native state in an ATP‐dependent way. It was established that the mechanism of ClpB action depends on the formation of a ring‐shaped hexameric structure and the translocation of a protein substrate through an axial channel. The structural aspects of this process are not fully known. By means of homology modeling and protein–protein docking, we obtained a model of the hexameric arrangement of the full‐length ClpB protein complexed with ATP. A molecular dynamics simulation of this model was performed to assess its flexibility and conformational stability. The high mobility of the “linker” M‐domain, essential for the renaturing activity of ClpB, was demonstrated, and the size and shape of central channel were analyzed. In this model, we propose the coordinates for a loop between b4 and B6 structural elements, not defined in previous structural research, which faces the inside of the channel and may therefore play a role in substrate translocation. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 47–60, 2010.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Metabolic engineering of Escherichia coli for the production of putrescine: A four carbon diamine
Authors: Qian Zhi‐Gang , Xia Xiao‐Xia , Lee Sang Yup 
Published: August 2009

AbstractA four carbon linear chain diamine, putrescine (1,4‐diaminobutane), is an important platform chemical having a wide range of applications in chemical industry. Biotechnological production of putrescine from renewable feedstock is a promising alternative to the chemical synthesis that originates from non‐renewable petroleum. Here we report development of a metabolically engineered strain of Escherichia coli that produces putrescine at high titer in glucose mineral salts medium. First, a base strain was constructed by inactivating the putrescine degradation and utilization pathways, and deleting the ornithine carbamoyltransferase chain I gene argI to make more precursors available for putrescine synthesis. Next, ornithine decarboxylase, which converts ornithine to putrescine, was amplified by a combination of plasmid‐based and chromosome‐based overexpression of the coding genes under the strong tac or trc promoter. Furthermore, the ornithine biosynthetic genes (argC‐E) were overexpressed from the trc promoter, which replaced the native promoter in the genome, to increase the ornithine pool. Finally, strain performance was further improved by the deletion of the stress responsive RNA polymerase sigma factor RpoS, a well‐known global transcription regulator that controls the expression of ca. 10% of the E. coli genes. The final engineered E. coli strain was able to produce 1.68 g L−1 of putrescine with a yield of 0.168 g g−1 glucose. Furthermore, high cell density cultivation allowed production of 24.2 g L−1 of putrescine with a productivity of 0.75 g L−1 h−1. The strategy reported here should be useful for the bio‐based production of putrescine from renewable resources, and also for the development of strains capable of producing other diamines, which are important as nitrogen‐containing platform chemicals. Biotechnol. Bioeng. 2009; 104: 651–662 © 2009 Wiley Periodicals, Inc.
Interaction of diphtheria toxin (fragment A) with actin
Authors: Bektaş Muhammet , Varol Başak , Nurten Rüstem , Bermek Engin 
Published: August 2009

AbstractIt was shown by gel filtration and viscosity measurements that N‐terminal fragment (FA) of diphtheria toxin (DT) can interact with both G‐ and F‐actin (filamentous actin). Elution profiles on Sephadex G‐100 indicated the formation of a binary complex of fragment A (FA) with globular actin monomer (G‐actin), which was inhibited by gelsolin. Deoxyribonuclease I (DNase I) in turn appeared to interact with this complex. Tritiated FA was found to bind to F‐actin stoichiometrically. This binding was inhibited again by gelsolin and G‐actin, but not by DNase I. The binding of FA inhibited polymerization of G‐actin and induced a time‐dependent breakdown of F‐actin under polymerization conditions. Inhibition of its ADP‐ribosyltransferase activity did not have any effect on the interactions of FA with actin. FA interacted with actin also in the cell. After treatment of human umbilical vein endothelial cells (HUVEC) with biotin‐labeled DT, Western blot analysis revealed predominantly the presence of actin in affinity‐isolated complexes of the labeled FA. Similarly, FA was found in immunoaffinity‐isolated complexes of actin. Copyright © 2009 John Wiley & Sons, Ltd.
Polymorphisms of DNA base‐excision repair genesAPE/Ref‐1andXRCC1are not associated with the risk for Graves' disease
Authors: Doğru‐Abbasoğlu Semra , Tanrıkulu Sevda , Ademoğlu Evin , Erbil Yeşim , Özderya Ayşenur , Karadağ Berrin , Uysal Müjdat 
Published: August 2009

AbstractOxidative stress has been implicated in etiopathogenesis of Graves' disease (GD). Increased lipid peroxidation and oxidative DNA damage have been found in GD patients. Oxidative DNA damage is mainly repaired by the base‐excision repair (BER) pathway. Polymorphisms in DNA‐repair genes have been associated with the increased risk of various diseases and could also be related to the etiology of GD. Therefore, we conducted a study including 197 patients with GD and age‐ and sex‐matched 303 healthy subjects to examine the role of single‐nucleotide polymorphisms of BER genes, APE/Ref‐1 (codon 148) and XRCC1 (codons 194 and 399) as a risk factor for GD. These polymorphisms were determined by quantitative real‐time PCR and melting curve analysis using LightCycler. No significant association was observed between the variant alleles of APE/Ref‐1 codon 148 [odds ratio (OR) = 0.89, 95% confidence interval (CI) = 0.69–1.17], XRCC1 codon 194 (OR = 1.24, 95% CI = 0.79–1.94), and XRCC1 codon 399 (OR = 1.12, 95% CI = 0.86–1.46) and GD. These preliminary results suggest that APE/Ref‐1 (codon 148) and XRCC1 (codons 194 and 399) polymorphisms are not significant risk factors for developing GD. Copyright © 2009 John Wiley & Sons, Ltd.
Highly Efficient Asymmetric Synthesis of Vinylic Amino Alcohols by Zn‐Promoted Benzoyloxyallylation of Chiral N‐tert‐Butanesulfinyl Imines: Facile and Rapid Access to (−)‐Cytoxazone
Authors: Liu Min , Sun Xing‐Wen , Xu Ming‐Hua , Lin Guo‐Qiang 
Published: August 2009

AbstractAn efficient and convenient α‐hydroxyallylation approach for the asymmetric synthesis of a variety of β‐amino‐α‐vinyl alcohols has been successfully developed. A wide range of vinylic amino alcohol derivatives could be obtained in very good yields and with excellent diastereomeric ratios of up to 99:1 in favor of anti isomers by highly diastereoselective Zn‐promoted benzoyloxyallylation of chiral N‐tert‐butanesulfinyl imines with 3‐bromopropenyl benzoate at room temperature. In particular, excellent enantioinduction of the two new stereogenic centers was observed, with up to 98 % ee. The method provides a new route for the direct α‐hydroxyallylation of imines in a highly stereoselective manner. Moreover, the synthetic value of the method has also been demonstrated by the most concise and straightforward synthesis of (−)‐cytoxazone yet reported.
Ligand Strain and the Nature of Spin Crossover in Binuclear Complexes: Two‐Step Spin Crossover in a 4,4′‐Bipyridine‐Bridged Iron(II) Complex [{Fe(dpia)(NCS)2}2(4,4′‐bpy)] (dpia=di(2‐picolyl)amine; 4,4′‐bpy=4,4′‐bipyridine)
Authors: Verat Alexander Yu. , Ould‐Moussa Nawel , Jeanneau Erwann , Le Guennic Boris , Bousseksou Azzedine , Borshch Serguei A. , Matouzenko Galina S. 
Published: August 2009

AbstractThe synthesis and detailed characterization of the new spin crossover (SCO) binuclear complex [{Fe(dpia)(NCS)2}2(4,4′‐bpy)] (1; dpia=di(2‐picolyl)amine, 4,4′‐bpy=4,4′‐bipyridine) are reported. Variable‐temperature magnetic susceptibility measurements show a relatively cooperative two‐step spin transition suggesting the occurrence of three spin‐state isomers: [HS–HS], [HS–LS], and [LS–LS] (HS: high spin, LS: low spin). A short plateau at 204 K separates the two steps and conforms with about 50 % of the complexes having undergone a thermal spin conversion. Routine Mössbauer spectroscopy without applying a magnetic field clearly separates four iron(II) one‐center spin states in three [HS–HS], [HS–LS], and [LS–LS] pairs and unambiguously confirms that the spin transition at the plateau temperature goes through the intermediate [HS–LS] state. The single‐crystal X‐ray structure was solved for three spin isomers at 293, 208, and 120 K. The structural study at the plateau temperature was unable to resolve the HS and LS sites in the [HS–LS] pair and only an average FeN bond length was obtained, which suggests that there is an intermediate [HS–LS] phase. The structural analysis at three temperatures revealed a dense three‐dimensional network of both intra‐ and intermolecular interactions. The relative energies of the three spin‐state isomers were evaluated by quantum‐chemical DFT calculations. Comparison of compound 1 with previously known analogues, as well as the overall analysis of structural data for numerous binuclear complexes, allowed a conclusion to be reached on the crucial role of ligand strain effects in the SCO behavior of binuclear complexes. The suggested intramolecular mechanism explains the different types of SCO observed in binuclear complexes: one‐step, two‐step, and partial (50 %) transitions.
Lewis Base Sequestered Chalcogen Dihalides: Synthetic Sources of ChX2 (Ch=Se, Te; X=Cl, Br)
Authors: Dutton Jason L. , Farrar Gregory J. , Sgro Michael J. , Battista Taylor L. , Ragogna Paul J. 
Published: August 2009

AbstractThe synthesis and comprehensive characterization of a series of base‐stabilized ChX2 (Ch=Se, Te; X=Cl, Br) is reported using aryl‐substituted diazabutadiene and 2,2′‐bipyridine (bipy) as the ligands. In stark contrast to free ChX2 the complexes display excellent thermal stability. Their use as viable ChX2 reagents that may be stored for later use is demonstrated in principle. The syntheses are simple and high‐yielding from commercially available or easily synthesized reagents. The bipy complexes are exceedingly rare examples of this ubiquitous ligand being utilized within Group 16 chemistry; the Se examples are the first to be characterized by X‐ray crystallography, and the Te species are only the second.
Change in the Site of Electron‐Transfer Reduction of a Zinc–Quinoxalinoporphyrin/Gold–Quinoxalinoporphyrin Dyad by Binding of Scandium Ions and the Resulting Remarkable Elongation of the Charge‐Shifted‐State Lifetime
Authors: Ohkubo Kei , Garcia Rachel , Sintic Paul J. , Khoury Tony , Crossley Maxwell J. , Kadish Karl M. , Fukuzumi Shunichi 
Published: August 2009

AbstractThe site of electron‐transfer reduction of AuPQ+ (PQ=5,10,15,20‐tetrakis(3,5‐di‐tert‐butylphenyl)quino‐xalino[2, 3−b′]porphyrin) and AuQPQ+ (QPQ=5,10,15,20‐tetrakis(3,5‐di‐tert‐butylphenyl)bisquinoxalino[2,3‐b′:12,13‐b′′]porphyrin) is changed from the AuIII center to the quinoxaline part of the PQ macrocycle in the presence of Sc3+ in benzonitrile because of strong binding of Sc3+ to the two nitrogen atoms of the quinoxaline moiety. Strong binding of Sc3+ to the corresponding nitrogen atoms on the quinoxaline unit of ZnPQ also occurs for the neutral form. The effects of Sc3+ on the photodynamics of an electron donor–acceptor compound containing a linked ZnII and AuIII porphyrin ([ZnPQ–AuPQ]PF6) have been examined by femto‐ and nanosecond laser flash photolysis measurements. The observed transient absorption bands at 630 and 670 nm after laser pulse irradiation in the absence of Sc3+ in benzonitrile are assigned to the charge‐shifted (CS) state (ZnPQ.+–AuPQ). The CS state decays through back electron transfer (BET) to the ground state rather than to the triplet excited state. The BET rate was determined from the disappearance of the absorption band due to the CS state. The decay of the CS state obeys first‐order kinetics. The CS lifetime was determined to be 250 ps in benzonitrile. Addition of Sc3+ to a solution of ZnPQ–AuPQ+ in benzonitrile caused a drastic lengthening of the CS lifetime that was determined to be 430 ns, a value 1700 times longer than the 250 ps lifetime measured in the absence of Sc3+. Such remarkable prolongation of the CS lifetime in the presence of Sc3+ results from a change in the site of electron transfer from the AuIII center to the quinoxaline part of the PQ macrocycle when Sc3+ binds to the quinoxaline moiety, which decelerate BET due to a large reorganization energy of electron transfer. The change in the site of electron transfer was confirmed by ESR measurements, redox potentials, and UV/Vis spectra of the singly reduced products.
Elucidating the Structure of the Pm$\bar 3$n Cubic Phase of Supramolecular Dendrimers through the Modification of their Aliphatic to Aromatic Volume Ratio
Authors: Percec Virgil , Peterca Mihai , Tsuda Yusuke , Rosen Brad M. , Uchida Satoshi , Imam Mohammad R. , Ungar Goran , Heiney Paul A. 
Published: August 2009

AbstractThe synthesis, and structural and retrostructural analysis of a library of second‐generation conical dendrons that self‐assemble into spherical supramolecular dendrimers is reported. This library consists of amphiphilic dendrons with n‐alkyl groups containing from 4 to 16 carbon atoms. The dendrons containing 6 to 16 carbon atoms in their n‐alkyl groups self‐assemble into spherical supramolecular dendrimers that self‐organize in a Pm$\bar 3$n cubic lattice. The structural and retrostructural analysis of the Pm$\bar 3$n lattices generated from the supramolecular dendrimers demonstrated that the volume of the aromatic core of the spherical dendrimers is not dependent on the number of carbon atoms from their alkyl groups. This result facilitated the calculation of the average values of the absolute electron density of the aliphatic and aromatic domains of the spherical supramolecular dendrimers. The relative intensity of the higher order diffraction peaks of the Pm$\bar 3$n lattice increases as the volume of the aliphatic part of the sphere mediated by the number of carbon atoms in the n‐alkyl groups decreases. This study demonstrates the maximum increase of the relative intensity of the higher order diffraction peaks of the Pm$\bar 3$n lattice generated from non‐hollow supramolecular dendrimers.
ChemInform Abstract: Enantioselective Conjugate Addition of N‐Heterocycles to α,β‐Unsaturated Ketones Catalyzed by Chiral Primary Amines.
Authors: Luo Guangshun , Zhang Shilei , Duan Wenhu , Wang Wei 
Published: August 2009

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Investigation on the Scavenging Mechanism of 1,4‐Dicarbonyls by Pyridoxamine: A Density Functional Theory Study
Authors: CHEN Xin , QIAO Qingan , CAI Zhengting , JIN Yueqing , JING Jie , SUN Xiaomin , SUN Lixiang , CAI Honglan , FENG Dacheng 
Published: August 2009

AbstractThe dicarbonyl compound 4‐oxopentanal (OPA) is one of the reactive carbonyl species formed in a variety of metabolic reactions in vivo, which could react with lysyl residues to form pyrrolic compounds and exhibit severe toxicity. Pyridoxamine (PM) could effectively scavenge such reactive carbonyl compounds. The reaction mechanism of PM with OPA was investigated by density functional theory (DFT) B3LYP at 6‐31G∗︁ basis level together with MP2/6‐31+G∗︁∗︁ single point calculation on the stationary points. The results indicated that this reaction could be achieved through two continuous steps. Firstly, PM and OPA would generate a tetrahydropyrrole compound via two possible reaction pathways. Subsequently, two molecules of water would be removed to achieve the final pyrrole‐type compound through two parallel paths. In addition, it is possible to form an imine intermediate in this reaction, which seems more like a by‐product from our calculation. In the end, the steric hindrance of the acetyl group was discussed. All the results agreed with experiment very well.
Manganese Dioxide Mediated Stereoselective, One‐step Synthesis of Novel Steroidal (6R)‐Spiro‐1',2′,4′‐triazoline‐3′‐thiones
Authors: SHAMSUZZAMAN  , SIDDIQUI Nazish , SALIM Anwar , AKRAM M. K. 
Published: August 2009

AbstractOxidative cyclization of 5α‐cholestan‐6‐one thiosemicarbazone (1), its 3β‐chloro (2) and 3β‐acetoxy (3) analogues with active manganese dioxide at room temperature afforded selectively the corresponding (6R)‐spiro‐1',2′,4′‐triazoline‐3′‐thiones 4–6. This synthesis has the advantages of mild reaction conditions, easy handling, easily available reagent and high yields. The products have been characterized by analytical and spectral data.
Colorimetric Sensors for Anion Recognition Based on the Proton Transfer Signaling Mechanism
Authors: HUANG Xiaohuan , HE Yongbing , CHEN Zhihong , HU Chenguang 
Published: August 2009

AbstractPhenolic hydroxyl based sensors N,N‐bi(salicylidene)‐1,2‐phenylenediamine (1), 2‐[(4‐nitrophenylimino)‐ methyl] phenol (2) and 2‐[p‐tdylimino methyl] phenol (3) bearing Schiff‐base groups can act as selective colorimetric sensors for anions, which exhibit distinct color changes in the presence of fluoride, but show no response to other halogen anions. They also give response to acetate, which is clearly visible to the naked eyes. The selectivity can be rationalized on the proton transfer signaling mechanism. The sensor 1 containing plural phenolic groups undergoes stepwise deprotonation of the two O–H fragments when it interacts with excess fluoride, which is confirmed by UV‐Vis, 1H NMR and 19F NMR spectroscopic methods.
Synthesis of Novel Bis‐spiroisoxazolines through 1,3‐Dipolar Cycloaddition of Nitrile Oxide with α,α'‐Bis(arylmethylidene)cycloalkanone
Authors: LI Xiaofang , YU Xianyong , FENG Yaqing 
Published: August 2009

AbstractA new class of bis‐spiroisoxazolines were prepared in moderate to good yields in a highly regioselective cycloaddition of nitrile oxide with bis(arylmethylidene)cycloalkanone. The structures of the products were characterized thoroughly by IR, elemental analysis, NMR together with X‐ray crystallographic analysis. The result of crystal diffraction indicates that this 1,3‐dipolar cycloaddition has high regioselectivity. The density functional calculations provide a reasonable explanation on the regioselectivity for the cycloaddition reaction.
Synthesis of Thermostable Azo‐type Photoswitches towards Photoregulating Nucleic Acid Structures
Authors: WANG Qi , GAO Shuang , ZHOU Kai , CHEN Wenbin , NIU Congwei , XI Zhen 
Published: August 2009

AbstractIn order to design efficient and thermostable azo‐type regulators, a series of azo‐type compounds were synthesized and characterized. While introducing an inductive electron‐withdrawing group to an azobenzene para or meta‐position, the obtained compound can be an excellent photoswitch. 3,3′‐Azo‐di‐benzyl alcohol was designed and synthesized as one of thermostable and efficient photoswitches, which can efficiently reversibly photoregulate the nucleic acid structure with its cis‐isomer being sufficiently stable at physiological temperature.
Synthesis of a Number of 3‐Alkyl Substituted Pyrrole Monomers
Authors: CAI Xuediao , JAEHNE Evelin , ADLER Hans‐Juergen 
Published: August 2009

AbstractThe problem of delamination of electro‐deposited polypyrrole (PPY) layers on several substrates can be avoided by using an adhesion promoting system. A new class of compounds–ω‐(pyrrol‐3‐yl)alkylphosphonic acids have been designed to link polypyrrole layers covalently to metal oxide surfaces. Synthetic routes, which lead to the formation of 3‐substituted pyrroles with surface active groups are described. The synthesis and characterization are shown in detail. 1‐Phenylsulfonyl pyrrole was utilized as a precursor in the synthesis of 3‐substituted pyrroles via Friedel‐Crafts acylation reaction. Subsequently, two methods were used to synthesize ω‐(pyrrol‐3‐yl)alkylpho‐ sphonic acid esters. One starts from the brominated oxoalkyl derivatives by removing the protecting group followed by reduction yielding ω‐(pyrrol‐3‐yl)alkylphosphonic acid esters. This method is suitable for hexyl or longer chain derivatives. The other is the reduction of carbonyl group followed by de‐protection, which is successful for short as well as long chain derivatives. Finally, ω‐(pyrrol‐3‐yl)alkylphosphonic acids were obtained by hydrolysis of the ester derivatives.
An Unexpected and Efficient Synthesis of Open‐chain Derivatives of Bistetronic Acid under Microwave Irradiation
Authors: SHI Feng , MA Ning , ZHOU Dianxiang , ZHANG Ge , JIANG Bo , TU Shujiang 
Published: August 2009

AbstractAn unexpected and efficient synthesis of novel open‐chain derivatives of bistetronic acid has been successfully achieved in glyclol under microwave irradiation (MW). This method has the prominent advantages of short reaction time, high yield, operational simplicity as well as environmental friendliness.
Synthesis and Properties of Poly(vinyl alcohol)/Synthetic F‐montmorillonite Nanocomposites
Authors: ZHANG Junhao , CHENG Xiaofang , LIU He , LU Weiliang 
Published: August 2009

AbstractF‐montmorillonite (F‐MMT) was synthesized by a hydrothermal method at 493 K for 72 h, in which a little of hydroxyl radical is replaced by fluoride ion in the silicate structure. Poly(vinyl alcohol) (PVA)/F‐MMT nanocomposites were prepared using the synthetic F‐MMT by a solution‐intercalation method. The F‐MMT and PVA/ F‐MMT nanocomposites were characterized by X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results indicate that the flake structured F‐MMT is homogeneously dispersed in PVA, forming an exfoliated nanocomposite structure. Thermogravimetric analysis, mechanical performance and UV‐visible spectroscopy were applied to test the properties of PVA nanocomposites, which indicate that the thermal stability and mechanical performance are enhanced distinctly, without a sacrifice in optical clarity. The improvement of mechanical and thermal properties was attributed to the homogeneous and good dispersion of F‐MMT in polymeric matrix and the strong hydrogen bonding between O��H of PVA and F�� of F‐MMT.