bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of ibuprofen in pharmaceutical formulations using time‐resolved terbium‐sensitized luminescence
Authors: Al‐Kindy Salma M. Z. , Suliman Fakhr Eldin O. 
Published: March 2007

AbstractA sensitive and specific luminescence method for the determination of ibuprofen (IB) in pharmaceutical formulations in aqueous solution is described. The method is based on the luminescence sensitization of terbium (Tb3+) by formation of ternary complex with IB in the presence of tri‐n‐octylphosphine oxide (TOPO) and Tween‐20 as surfactant. The luminescence signal for Tb–IB–TOPO is monitored at λex = 229 nm and λem = 545 nm. Optimum conditions for the formation of the complex in aqueous system, were 16 mmol/L TRIS buffer, pH 5.7, TOPO 200 µmol/L and 15 µmol/L of Tb3+, which allows for the determination of 9.7 × 10−7 – 9.7 × 10−6 mol/L IB with a detection limit of 1.2 × 10−7 mol/L. The relative standard deviations of the method were <1.4%, indicating excellent reproducibility. The proposed method was successfully applied for the assays of IB in pharmaceutical formulations with average recoveries of 100.3–102.5%. Copyright © 2007 John Wiley & Sons, Ltd.
Heterologous expression and characterization of recombinant glycerol dehydratase from Klebsiella pneumoniae in Escherichia coli
Authors: Wang Fenghuan , Qu Huijin , Tian Pingfang , Tan Tianwei 
Published: March 2007

AbstractGlycerol dehydratase (EC 4.2.1.30), as one of the key enzymes in converting glycerol to the valuable intermediate 1,3‐propanediol, is important for biochemical industry. The dhaB genes encoding coenzyme B12‐dependent glycerol dehydratase in Klebsiella pneumoniae were cloned and expressed in Escherichia coli. An effective co‐expression system of multiple subunits protein was constructed. Heterologous expression vectors were constructed using the splicing by overlap extension‐PCR technique to co‐express the three subunits of the glycerol dehydratase. After induction by isopropyl‐β‐D‐thiogalactopyranoside, SDS‐PAGE analysis revealed that: (i) only the α subunit of glycerol dehydratase was expressed in direct expression system, (ii) the three subunits of glycerol dehydratase with predicted molecular massess of 64 (agr;), 22 (β), and 16 kDa (γ) were expressed simultaneously in co‐expression system, and (iii) the fusion expression system expressed the fusion protein of 99 kDa. Enzyme assay showed that the activities of three heterologous expression products were 27.4, 2.3, and 0.2 U/mg. The highest enzyme activity was almost 17 times of that in K. pneumoniae. The recombinant enzyme was purified and biochemically characterized. The apparent Km values of the enzyme for coenzyme B12 and 1, 2‐propanediol were 8.5 nM and 1.2 mM, respectively. The enzyme showed maximum activity at pH 8.5 and 37°C.
Application of cellulose‐based self‐assembled tri‐enzyme system in a pseudo‐reagent‐less biosensor for biogenic catecholamine detection
Authors: Rabinovich Mikhail L. , Vasil'chenko Liliya G. , Karapetyan Karen N. , Shumakovich Galina P. , Yershevich Olga P. , Ludwig Roland , Haltrich Dietmar , Hadar Yitzhak , Kozlov Yuri P. , Yaropolov Alexander I. 
Published: March 2007

AbstractAmorphous cellulose was used as a specific carrier for the deposition of self‐assembled multienzyme complexes capable of catalyzing coupled reactions. Naturally glycosylated fungal cellobiohydrolases (CBHs) of glycosyl hydrolase families 6 and 7 were specifically deposited onto the cellulose surface through their family I cellulose‐binding modules (CBM). Naturally glycosylated fungal laccase was then deposited onto the preformed glycoprotein layer pretreated by ConA, through the interaction of mannosyl moieties of fungal glycoproteins with the multivalent lectin. The formation of a cellulase‐ConA‐laccase composite was proven by direct and indirect determination of activity of immobilized laccase. In the absence of cellulases and ConA, no laccase deposition onto the cellulose surface was observed. Finally, basidiomycetous cellobiose dehydrogenase (CDH) was deposited onto the cellulose surface through the specific interaction of its FAD domain with cellulose. The obtained paste was applied onto the surface of a Clark‐type oxygen electrode and covered with a dialysis membrane. In the presence of traces of catechol or dopamine as mediators, the obtained immobilized multienzyme composite was capable of the coupled oxidation of cellulose by dissolved oxygen, thus providing the basis for a sensitive assay of the mediator. Swollen amorphous cellulose plays three different roles in the obtained biosensor as: (i) a gelforming matrix that captures the analyte and its oxidized intermediate, (ii) a specific carrier for protein self‐assembly, and (iii) a source of excess substrate for a pseudo‐reagent‐less assay with signal amplification. The detection limit of such a tri‐enzyme biosensor is 50‐100 nM dopamine.
Comprehensive survey of p94/calpain 3 substrates by comparative proteomics – Possible regulation of protein synthesis by p94
Authors: Ono Yasuko , Hayashi Chikako , Doi Naoko , Kitamura Fujiko , Shindo Mayumi , Kudo Kenichi , Tsubata Takuichi , Yanagida Mitsuaki , Sorimachi Hiroyuki 
Published: March 2007

AbstractCalpain represents a family of Ca2+‐dependent cytosolic cysteine proteases found in almost all eukaryotes and some bacteria, and is involved in a variety of biological phenomena, including brain function. Several substrates of calpain are aggressively proteolyzed under pathological conditions, e.g., in neurodegenerating processes, fodrin is proteolyzed by calpain. Because very small amounts of substrate are proteolyzed by calpain under normal biological conditions, the molecular identities of calpain substrates are largely unknown. In this study, an extensive survey of the substrates of p94/calpain 3 in COS7 cells was executed using iTRAQTM labeling and 2‐D LC‐MALDI analysis. p94 was used because: (i) several p94 splicing variants are expressed in brain tissue even though p94 itself is a skeletal‐muscle‐specific calpain, and (ii) it exhibits Ca2+‐independent activity in COS cells, which makes it useful for evaluating the effects of p94 protease activity on proteins without perturbing the cells. Our approach revealed several novel protein substrates for p94, including the substrates of conventional calpains, components of the protein synthesis system, and enzymes of the glycolytic pathway. The results demonstrate the usefulness and sensitivity of this approach for mining calpain substrates. A combination of this method with other analytical methods would contribute to elucidation of the biological relevance of the calpain family.
Bio‐electrosprays: A novel electrified jetting methodology for the safe handling and deployment of primary living organisms
Authors: Odenwälder Patrick K. , Irvine Scott , McEwan Jean R. , Jayasinghe Suwan N. 
Published: March 2007

AbstractElectrohydrodynamic jetting (EHDJ) which is also known as electrosprays (ES) has recently been elucidated as a unique electrified biotechnique for the safe handling and deployment of living organisms. This high intensity electric field driven jetting methodology is now referred to as “bioelectrosprays” (BES). Previously these charged jets have only been shown to jet‐process immortalized cells which have undergone expected cellular behavior when compared with control cells. In this paper we demonstrate the ability to jet process primary living organisms in the stable conejetting mode. Finally the viability of the bio‐electrosprayed living organisms has been assessed employing a flow cytometry approach which forms the discussion in this paper. Our findings further establish BES as a competing biotechnique, which could be employed for the deposition of primary living organisms according to a predetermined active cellular architecture. One day this could be used for the fabrication of viable tissues and organs for repair or replacement. These advanced studies carried out on BES have direct widespread applications ranging from developmental biology to regenerative and therapeutic medicine, which are a few amongst several other areas of study within the life sciences.
Scavenging effects of phenolic compounds on reactive oxygen species
Authors: Aboul‐Enein Hassan Y. , Kruk Irena , Kładna Aleksandra , Lichszteld Krzysztof , Michalska Teresa 
Published: March 2007

AbstractPhenolic compounds are widely present in plants and they have received considerable attention due to their antioxidant property. In this article we report the results of a study of the reactivity of 10 selected phenolics (sesamol, three phenolic acids, three flavonols, one flavone, and two flavanones) with superoxide anion radical (O), hydroxyl radical (HO•) and singlet oxygen (1O2). The following generators of reactive oxygen species were used: 18‐crown‐6/KO2/dimethylsulfoxide (DMSO) or hypoxanthine/xanthine oxidase as sources of O, the Fenton reaction carried out in a sodium trifluoroacetate (pH 6.15) for HO•, and a mixture of alkaline aqueous H2O2 and cobalt ions for 1O2. We have employed chemiluminescence, electron spin resonance spin trapping, and spectrophotometry techniques to examine an antioxidative property. All tested compounds acted as scavengers of various reactive oxygen species. The reactivity indexes (β) for the reaction of the phenolic compounds with HO• were calculated. © 2007 Wiley Periodicals, Inc. Biopolymers 86: 222–230, 2007.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
Electrocyclic Ring Opening of cis‐Bicyclo[m.n.0]alkenes: The Anti‐Woodward–Hoffmann Quest
Authors: Silva López Carlos , Nieto Faza Olalla , de Lera Ángel R. 
Published: March 2007

AbstractThe dubbed anti‐Woodward–Hoffmann ring‐opening reaction of cis‐bicyclo[4.2.0]oct‐7‐ene to yield cis,cis‐cycloocta‐1,3‐diene has been intensively studied with robust, high‐level computational methods. This reaction has been found to proceed through a conrotatory allowed pathway to afford cis,trans‐cycloocta‐1,3‐diene followed by E to Z isomerization, instead of a disrotatory forbidden pathway, as suggested. Computational calculations of kinetic isotope effects are consistent with this interpretation and the experimental values. The study of lower bicyclic homologues with [3.2.0], [2.2.0] and [2.1.0] skeletons indicates the feasibility of a mechanistic change towards the anti‐Woodward–Hoffmann disrotatory path. This is clearly favored for the ring opening of the highly strained cis‐bicyclo[2.1.0]pent‐2‐ene and is highly competitive with the conrotatory path for cis‐bicyclo[2.2.0]hex‐2‐ene. Therefore, the rearrangement of the smallest bicyclic cyclobutene is predicted computationally to be an anti‐Woodward–Hoffmann disrotatory electrocyclic ring‐opening reaction.
A Comparative Relativistic DFT and Ab Initio Study on the Structure and Thermodynamics of the Oxofluorides of Uranium(IV), (V) and (VI)
Authors: Shamov Grigory A. , Schreckenbach Georg , Vo Thach N. 
Published: March 2007

AbstractAll the possible uranium(VI, V, IV) oxides, fluorides and oxofluorides were studied theoretically by using density functional theory (DFT) in the generalised gradient approximation (GGA), and three different relativistic methods (all‐electron scalar four component Dyall RESC method (AE), relativistic small‐core ECPs, and zeroth order regular approximation ZORA). In order to test different correlation methods, for the two former relativistic methods hybrid DFT, and, for the AE method, MP2 molecular orbital calculations were performed as well. Single‐point AE‐CCSD(T) energies were calculated on MP2 geometries as well. Energies of the uranium(VI) and (V) oxofluorides dissociation, uranium(VI) fluoride hydrolysis and oxofluoride disproportionation were calculated and compared against the available experimental thermochemical data. AE‐CCSD(T) energies were the closest to the experiment. For GGA DFT methods, all the relativistic methods used yield similar results. For thermochemistry, the best quantitative agreement with the experimental and CCSD(T) values for both UO and UF bond strengths was obtained with hybrid DFT methods, provided that a reliable basis set was used. Both the GGA DFT and MP2 MO methods show overbinding of these bonds; moreover, this overbinding was found to be not uniform but strongly dependent on the coordination environment of the uranium atom in each case. UO vibrational frequencies given by hybrid DFT, however, are systematically overestimated, and are better reproduced by GGA DFT; MP2 values usually fall in‐between. Reaction enthalpies, UO frequencies and complex geometries given by the PBE, MPBE, BPBE, BLYP and OLYP GGA functionals are quite similar, with OLYP performing slightly better than the others but still not as good as hybrid DFT. The geometries of the molecules are found to be influenced by the following factors: the inverse transinfluence (ITI) of the oxygen ligand and, for UV, and UIV, the Jahn–Teller distortion.
Synthesis, Structure, and Characterization of Three Series of 3d–4f Metal‐Organic Frameworks Based on Rod‐Shaped and (6,3)‐Sheet Metal Carboxylate Substructures
Authors: Luo Feng , Batten Stuart R. , Che Yunxia , Zheng Ji‐Min 
Published: March 2007

AbstractThree series of porous lanthanide metal‐organic coordination polymers, namely [Cu(bpy)Ln3(ip)5(Hip)(H2O)] [Ln = Er (1 a), Y (1 b), Eu (1 c); bpy = 2,2′‐bipyridine, H2ip=isophthalic acid], [Cu3(bpy)2Ln2(ip)6(H2O)5] [Ln = Yb (2 a), Gd (2 b), Tb (2 c)], and [Cu3Ln2(ip)6] [Ln = Eu (3 a), Gd (3 b)] have been synthesized hydrothermally by the reaction of the combination of 3d–4f metal centers and N‐/O‐donor ligands. X‐ray diffraction analyses reveal that polymers 1 a–c and 2 a–c, as well as 3 a, b are isomorphous in structure. Polymers 1 a–c consist of 3D α‐Po networks based on a inorganic rod‐shaped secondary building units (SBUs) of {Er6Cu2(bipy)2(O2C)11} which are 27.03 Å in length. Polymers 2 a–c also contain 3D α‐Po networks, constructed from shorter (14.79 Å) but similarly rod‐shaped SBUs of {Yb2Cu3(bpy)2(O2C)12}. The structure also contains hydrogen‐bonded (H2O)6 chains which can be reversibly dehydrated/rehydrated. Polymers 3 a, b contain metal carboxylate substructures which have 2D (6,3) topologies; these layers are bridged by the ip2− ligands to give an overall 3D network which contains two sorts of cavities. This series of Ln–Cu coordination polymers are further characterized by antiferromagnetic behavior.
Icosahedral and Ring‐Shaped Allotropes of Phosphorus
Authors: Karttunen Antti J. , Linnolahti Mikko , Pakkanen Tapani A. 
Published: March 2007

AbstractThe existence of two new allotropic forms of phosphorus, icosahedral cages and ring‐shaped chains, is predicted. The cages and rings are nanostructural modifications of the black and the red phosphorus, respectively. The icosahedral and ring‐shaped allotropes are compared with the experimentally known allotropic forms of phosphorus by quantum chemical methods. Both the cages and the rings are thermodynamically favored over the white phosphorus, the rings being comparable to the Hittorf's violet phosphorus and to the recently discovered fibrous red phosphorus. The stabilities of the icosahedral cages increase as a function of their size, having structural resemblance with the rhombohedral black phosphorus. The high thermodynamic stability of the phosphorus nanostructures suggests their experimental synthesis to be viable.
Specific Recognition of Human Telomeric G‐Quadruplex DNA with Small Molecules and the Conformational Analysis by ESI Mass Spectrometry and Circular Dichroism Spectropolarimetry
Authors: Zhou Jiang , Yuan Gu 
Published: March 2007

AbstractElectrospray ionization mass spectrometry (ESI‐MS) was utilized to investigate the binding affinity and stoichiometry of small molecules with human telomeric G‐quadruplex DNA. The binding‐affinity order obtained for the (AGGGTT)4 quadruplex was: Tel01>ImImImβDp≫PyPyPyγImImImβDp. The specific binding of Tel01 and PyPyPyγImImImβDp in one system consisting of human telomeric G‐quadruplex and duplex DNA was observed directly for the first time. This revealed that PyPyPyγImImImβDp has a binding specificity for the duplex DNA, whereas Tel01 selectively recognizes the G‐quadruplex DNA. Moreover, both ESI‐MS and circular dichroism (CD) spectra indicated that Tel01 favored the formation and stabilization of the antiparallel G‐quadruplex, and a structural transition of the (AGGGTT)4 sequence from a coexistence of parallel and antiparallel G‐quadruplexes to a parallel G‐quadruplex induced by annealing.
Intramolecular Reactions in Pseudo‐Geminally Substituted [2.2]Paracyclophanes
Authors: Bondarenko Lidija , Hentschel Silke , Greiving Helmut , Grunenberg Jörg , Hopf Henning , Dix Ina , Jones Peter G. , Ernst Ludger 
Published: March 2007

AbstractA selection of pseudo‐geminally substituted [2.2]paracyclophanes, the alkynes 6, 7, 10, 11 a, and 11 b and the alkenes 8 and 9 were prepared for the study of intraannular reactions between functional groups in direct juxtaposition. Whereas 9 and 10 provide the corresponding cyclobutane and cyclobutene derivatives on irradiation (12 and 13, respectively), the bis‐alkynes 7 and 11 b do not lead to a cyclobutadiene intermediate. In the latter case the “half‐closed” butadiene derivative 17 was isolated. A Paterno–Büchi reaction took place on irradiation of 8 and 6, although the oxetene intermediate 21 produced in the second example did not survive the reaction conditions (ring‐opening to 22). Bromine addition to 9, 10, and 7 occurred with high stereoselectivity (formation of the dibromides 27, 30, and 33, respectively), and is rationalized by postulating the formation of the cationic intermediates 26, 29, and 32, respectively. To study the interaction of a carbocation with a facing triple bond, the alcohol 34 was prepared from 6. On acid treatment ring closure to the triply‐bridged phane 38 took place, accompanied by the hydration of the triple bond to the ketoalcohol 37. In an interesting intraannular [2+3]cycloaddition reaction the bis‐acetylene 11 a, on treatment with n‐butyl lithium, provided the cyclopentadiene derivative 42. That the two triple bonds of a pseudo‐geminal diacetylene can engage in a cyclization reaction leading to the cyclopentadienone complex 44 was also shown by treating 11 b with iron pentacarbonyl.
Conformation‐Dependent Racemization of Aspartyl Residues in Peptides
Authors: Kuge Katsunori , Brack André , Fujii Noriko 
Published: March 2007

AbstractBiologically uncommon D‐aspartyl (D‐Asp) residues have been detected in proteins of various tissues of elderly humans. The presence of D‐Asp has been explained as a result of the racemization of L‐Asp (denoted as Asp) in the protein of inert tissues. We have previously suggested that the racemization of Asp may depend on the conformation of the peptide chain. However, the nature of the peptide conformation that affects the D‐Asp formation has not yet been examined. Here we report the kinetics of Asp racemization in two model peptides, (Asp‐Leu)15 and (Leu‐Asp‐Asp‐Leu)8‐Asp, which form β‐sheet structures and α‐helical structures, respectively. For the β‐sheet structures, the activation energy of racemization of Asp residues was 27.3 kcal mol−1, the racemization rate constant at 37 °C was 2.14×10−2 per year and the time required to reach a D/L ratio of 0.99 at 37 °C was 122.6 years as estimated from the Arrhenius equation. For the α‐helical structures, the activation energy of racemization was 18.4 kcal mol−1, the racemization rate constant 20.02×10−2 per year and the time 13.1 year. These results suggest that Asp residues inserted in α‐helical peptides are more sensitive to racemization than Asp residues inserted in peptides adopting β‐sheet structures. The results clearly indicate that the racemization rate of Asp residues in peptides depends on the secondary structure of the host peptide.
Cyanation: Providing a Three‐in‐One Advantage for the Design of n‐Type Organic Field‐Effect Transistors
Authors: Kuo Ming‐Yu , Chen Hsing‐Yin , Chao Ito 
Published: March 2007

AbstractThe theoretical work presented here demonstrates that, when substitution takes place at appropriate positions, cyanation could be a useful tool for reducing the internal reorganization energy of molecules. A molecular‐orbital‐based explanation is given for this fundamentally important phenomenon. Some of the cyanated pentacene derivatives (nCN‐PENT‐n) not only have internal reorganization energies for electron transfer (λ−) smaller than that of pentacene, but the λ− values are even of the same magnitude as the internal reorganization energy for hole transfer (λ+) of pentacene, a small value that few organic compounds have surpassed. In addition, cyanation raises the electron affinity of the parent compound and may afford good electronic couplings between neighboring molecules, because of its ability in promoting π‐stacking. For the design of high performance n‐Type Organic field‐effect transistors, high electron affinities, large intermolecular electronic couplings, and small reorganization energies are necessary. Cyanation may help in all three aspects. Two cyanated trialkylsilylethynyl pentacene derivatives with known π‐stacking structures are predicted to provide reasonably small internal reorganization energies, large electronic couplings, and high electron affinities. They have the potential to outperform N‐fluoroalkylated dicyanoperylene‐3,4:9,10‐bis(dicarboximides) (PDI‐FCN2) in terms of electron mobility.
Towards the Design of Neutral Molecular Tweezers for Anion Recognition
Authors: Hermida‐Ramón Jose M. , Estévez Carlos M. 
Published: March 2007

AbstractMolecular tweezers are simple molecular receptors that can be characterized by the presence of two flat pincers separated by a more or less rigid tether. They have the ability to form complexes with a substrate molecule by gripping the substrate between the tips of the tweezers in a similar manner to that of mechanical tweezers. Klärner et al. synthesized one of the structurally simplest molecular tweezers, which is reported to bind electrodeficient aromatic and aliphatic substrates as well as organic cations. Complexes between these molecular tweezers and electron‐rich aromatic, aliphatic, or anionic substrates have not been observed. Inspired by several recent reports that describe the interaction of hexafluorobenzene with electron‐rich sites of molecules, we conducted a theoretical study to show the possibility of building molecular tweezers, based on those synthesized by Klärner, which were able to bind to anions and thus increase their potential as molecular receptors. We characterized complexes formed between several fluorinated derivatives of simple tweezers and an iodine anion, and analyzed the nature of the intermolecular interactions as well as the energetics for the process of complexation. The stabilization trend reflected by the energetic results when fluorine substituents were added to benzene rings confirms our hypothesis about the possibility of obtaining neutral tweezers composed of aromatic rings that can bind anions.