bluuebunny/crossref_metadata_2025_split huggingface dataset:
Capillary electrophoresis and enzyme solid phase assay for examining the purity of a synthetic heparin proteoglycan‐like conjugate and identifying binding to basic fibroblast growth factor
Authors: Dimitrellos V. , Lamari F. N. , Militsopoulou M. , Kanakis I. , Karamanos N. K. 
Published: February 2003

AbstractInteraction of basic fibroblast growth factor (bFGF) with heparin/heparan sulfate proteoglycans protects the growth factor against proteolytic degradation and is essential for its cellular activity. Although the structural requirements of heparin and heparan sulfate for the high‐affinity binding to bFGF have been extensively examined, studies on intact heparin proteoglycans are limited. In this report, the purity and the binding ability of a heparin proteoglycan‐like molecule—the heparin–bovine serum albumin (heparin–BSA) conjugate—was examined using capillary zone electrophoresis (CZE). Furthermore, the affinity of bFGF binding to the heparin‐BSA conjugate was studied using an enzyme solid‐phase assay. Chondroitin sulfate, dermatan sulfate, hyaluronan, heparan sulfate and variously sulfated disaccharides derived from heparin and heparan sulfate were also studied for their ability to compete with the binding of bFGF to heparin. Heparin–BSA conjugate was synthesized by reductive amination and, following precipitation with 1.5 vols of ethanol–sodium acetate, it was obtained free of contaminating heparin. Heparin–BSA–bFGF conjugate was obtained following incubation of heparin–BSA with bFGF for 2 h at 37°C. Intact heparin, heparin–BSA and heparin–BSA–bFGF conjugates were completely resolved by CZE using 50 mM phosphate, pH 3.5, as operating buffer, reversed polarity (30 kV) and detection at 232 nm. Competitive solid phase assay showed that, among the glycosaminoglycans tested, heparin exhibits the highest affinity binding to bFGF (IC50 = 6.4 nM). Heparan sulfate showed a lower affinity as compared with that of heparin, whereas all other glycosaminoglycans and heparin/heparan sulfate‐derived disaccharides tested showed minute effects. The developed CZE method is rapid and accurate and can be easily used to identify bFGF‐interacting heparin preparations of biopharmaceutical importance. Copyright © 2003 John Wiley & Sons, Ltd.
Fragmentation of Transition Metal Carbonyl Cluster Anions: Structural Insights from Mass Spectrometry
Authors: Butcher Colin P. G. , Dyson Paul J. , Johnson Brian F. G. , Khimyak Tetyana , McIndoe J. Scott 
Published: February 2003

AbstractThe anionic clusters [HOs5(CO)15]−, [PtRu5C(CO)15]2−, [Os10C(CO)24]2−, [Os17(CO)36]2−, [Os20(CO)40]3−, [Co6C(CO)15]2−, [Pt3Ru10C2(CO)32]2− and [Pd6Ru6(CO)24]2− have been analysed by energy‐dependent electrospray ionisation mass spectrometry (EDESI‐MS). Three main features have emerged. Firstly, carbonyl ligands are fragmented from clusters with compact metal cores in an orderly fashion, with each of the ions generated by CO loss having approximately equal intensity. Secondly, electron autodetachment takes place in multiply charged anionic clusters, but only after elimination of a large proportion of their carbonyl ligands. Thirdly, clusters with open metal cores do not undergo CO loss in an orderly fashion, but certain peaks are considerably less intense. The appearance of these low‐intensity peaks is believed to signify polyhedral core rearrangements, with open clusters folding to form more compact geometries. In some cases, the gas‐phase transformations observed by EDESI‐MS mirror those that are known to take place in solution.
Preorganization and Reorganization as Related Factors in Enzyme Catalysis: The Chorismate Mutase Case
Authors: Martí Sergio , Andrés Juan , Moliner Vicent , Silla Estanislao , Tuñón Iñaki , Bertrán Juan 
Published: February 2003

AbstractIn this paper a deeper insight into the chorismate‐to prephenate‐rearrangement, catalyzed by Bacillus subtilis chorismate mutase, is provided by means of a combination of statistical quantum mechanics/molecular mechanics simulation methods and hybrid potential energy surface exploration techniques. The main aim of this work is to present an estimation of the preorganization and reorganization terms of the enzyme catalytic rate enhancement. To analyze the first of these, we have studied different conformational equilibria of chorismate in aqueous solution and in the enzyme active site. Our conclusion is that chorismate mutase preferentially binds the reactive conformer of the substrate—that presenting a structure similar to the transition state of the reaction to be catalyzed—with shorter distances between the carbon atoms to be bonded and more diaxial character. With respect to the reorganization effect, an energy decomposition analysis of the potential energies of the reactive reactant and of the reaction transition state in aqueous solution and in the enzyme shows that the enzyme structure is better adapted to the transition structure. This means not only a more negative electrostatic interaction energy with the transition state but also a low enzyme deformation contribution to the energy barrier. Our calculations reveal that the structure of the enzyme is responsible for stabilizing the transition state structure of the reaction, with concomitant selection of the reactive form of the reactants. This is, the same enzymatic pattern that stabilizes the transition structure also promotes those reactant structures closer to the transition structure (i.e., the reactive reactants). In fact, both reorganization and preorganization effects have to be considered as the two faces of the same coin, having a common origin in the effect of the enzyme structure on the energy surface of the substrate.
Feste Zähne durch Kupfer
Authors: Jacoby Petra 
Published: February 2003

AbstractDie meisten Tiere härten ihre Zähne mit Calciumverbindungen. Anders jedoch der Meereswurm Glycera dibranchiata — er bildet ein kupferhaltiges Mineral und liefert mit dieser Strategie einen interessanten Ansatzpunkt zur Entwicklung neuer Werkstoffe.
Effect of Mn(II) ions on the growth of ammonium oxalate monohydrate crystals from aqueous solutions: I. Growth habit and surface morphology
Authors: Sangwal K. , Mielniczek‐Brzóska E. , Borc J. 
Published: February 2003

AbstractThe effect of concentration of Mn(II) ions on the growth habit and the surface micromorphology of different as‐grown faces of ammonium oxalate monohydrate (AO) single crystals grown from aqueous solutions was studied at a constant temperature of 30 °C and predefined supersaturations up to 20%. It was observed that the growth habit and the surface morphology of the crystals strongly depend on the supersaturation used for growth and the impurity concentration in the solution. The experimental results were analysed in terms of connected nets determined from different projections of the structure of AO crystals. Analysis of the observations revealed that: (1) the directions of connected nets corresponding to basic growth units composed of single (NH4)2C2O4 · H2O molecules are in excellent agreement with the low‐index crystallographic directions of the orientations of growth layers, (2) all faces appearing in the growth morphology of AO crystals are F faces, and (3) the {001} face growing from pure aqueous solutions is essentially a kinetically rough face but the presence of Mn(II) impurity leads to their appearance in the morphology due to increase in the strength of bonds of the connected nets composing the surface graph.
Effect of Mn(II) ions on the growth of ammonium oxalate monohydrate crystals from aqueous solutions: II. Growth kinetics
Authors: Sangwal K. , Mielniczek‐Brzóska E. 
Published: February 2003

AbstractThe experimental results of the effect of concentration of Mn(II) ions on the growth kinetics of different faces of ammonium oxalate monohydrate single crystals from aqueous solutions at a constant temperature and different predefined supersaturations are described and discussed. It was observed that: (1) at a given supersaturation σ, Mn(II) ions lead to a decrease in the growth rates of different faces of AO crystals, (2) the growth of a particular face of the crystals occurs above a critical supersaturation σd but there is also another supersaturation barrier σ* when the rate abruptly increases with σ, (3) the values of σd and σ* increase with increasing concentration of the impurity, and (4) the values of σd depend on the growth kinetics of a face but those of σ* are independent of face growth kinetics. The experimental R(σ) data for different Mn(II) concentrations ci were analysed according to the model involving complex source of cooperating screw dislocations and concepts of instantaneous and time‐dependent impurity adsorption. It was found that: (1) for a given face the differential heat of adsorption Qdiff is higher during instantaneous impurity adsorption than that during time‐dependent adsorption, and (2) the values of Qdiff involved during instantaneous adsorption are related with face growth kinetics but those during time‐dependent adsorption are independent of face growth kinetics.
A joint Japan–China research project for reducing pollution in China in the context of the Kyoto Protocol clean development mechanism (CDM): case study of the desulfurdized bio‐coal briquette experiments in Shenyang and Chengdu
Authors: Hayami Hitoshi , Nakamura Masao , Yoshioka Kanji 
Published: February 2003

AbstractThe Kyoto Protocol agreed on in 1997 allows some flexibility for developed countries in their implementations of their commitments to reduce emissions of CO2 and other global warming gases. In particular developed countries may receive emission credits for facilitating international cooperation for developing clean development mechanisms (CDMs) between themselves and developing countries. CDMs must reduce emissions of global warming gases on a sustainable basis in the developing countries involved. Such CDMs are expected to be an important tool for Japan and other developed countries for achieving their Kyoto Protocol commitments to reduce their CO2 emissions, but assessments and implementations of alternative CDMs require careful international joint research efforts. In this paper, we discuss our on‐going Japan–China joint research to develop and evaluate bio‐coal briquette (biobriquette), a new product to replace coal in some regions of China. Coal is a significant source of air pollution in China. The introduction of biobriquette use in China as a possible CDM for Japan is also discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Reaction thermodynamics of amine‐cured epoxy systems: Validation of the enthalpy and heat capacity of reaction as determined by modulated temperature differential scanning calorimetry
Authors: Swier Steven , Van Mele Bruno 
Published: February 2003

AbstractThe reaction enthalpy and reaction heat capacity of three aromatic epoxy–amine systems have been determined with modulated temperature diffential scanning calorimetry (MTDSC), mostly in quasi‐isothermal conditions, over a wide temperature range (33–140 °C) and for different mixture compositions. The reaction enthalpy is only slightly dependent on the epoxy–amine chemistry, from −111 to −98 kJ/mol epoxy functionality. With the model system phenyl glycidyl ether (PGE)+aniline, the reaction enthalpy of the secondary amine–epoxy reaction step is equal to that of the primary amine–epoxy reaction. Group contributions needed to calculate the reaction heat capacity with an additivity approach are evaluated, and a new value of 37.2 J mol−1 K−1 for the group N(H)(C)(CB) is proposed. With this group contribution, the additivity method predicts almost equal values for the reaction heat capacity of both amine–epoxy reaction steps at 298.15 K (ΔrCp,prim = 15.7 J mol−1 K−1 and ΔrCp,sec = 14.6 J mol−1 K−1), whereas the experimental value of ΔrCp,sec is about three times larger than that of ΔrCp,prim at 100 °C. These results are confirmed experimentally for PGE+aniline as a different temperature dependence of both reaction heat capacities. MTDSC therefore is potentially interesting for differentiating between reactive species in an epoxy–amine reaction, a benefit previously assigned to spectroscopic methods only. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 594–608, 2003
The value of product development lead time in software startup
Authors: Hilmola Olli‐Pekka , Helo Petri , Ojala Lauri 
Published: February 2003

AbstractThis article uses system dynamics simulation to enhance current understanding of the effects of product development lead time improvement in situations where a software company itself is not able to finance its operations with its own cash flow. In these situations, capital markets will provide some rounds of financing for startup at the very beginning, but after a while the company itself should be able to enlarge its operations with its own operational cash flow. However, the delay in the product development process, as well as the decline of R&D productivity within the final product markets, will have their effects. On the basis of the results of this article, it is suggested that the improvement of product development lead time is one of the most important parameters in the software startup environment. In some situations, not only will slightly improved lead time performance require fewer rounds of financing, but also expansion of the company's operations will become less troublesome. Copyright © 2003 John Wiley & Sons, Ltd.
Tailoring the software maintenance process to better support complex systems evolution projects
Authors: Donzelli Paolo 
Published: February 2003

AbstractWhen an organization considers the evolution of a software‐intensive system, the selection of the software maintenance process to be adopted must include consideration of the particular technical criteria, such as the application domain, the size and complexity of the final product, the hosting system characteristics, etc, yet be driven by the specific organization's goals, environment and maturity.By describing and analysing a real project, this paper shows how different approaches and techniques, usually applied in isolation, can be selected, customized and combined to implement a software maintenance and evolution process that better satisfies the goals and meets the constraints of the organization. The project was undertaken to investigate the feasibility of enhancing an aircraft avionics system by integrating new capabilities and, eventually, to identify a quick, low‐cost and low‐risk solution. Copyright © 2003 John Wiley & Sons, Ltd.
Geometry and thermomechanics of structural rearrangements: Ekkehart Kröner's legacy Plenary lecture presented at the 80th Annual GAMM Conference, Augsburg, 25‐28 March 2002
Authors: Maugin G.A. 
Published: February 2003

AbstractStarting with the influential ideas of E. Kröner on the Non‐Riemannian geometrical theory of defects and a brief review of his works, we show how this legacy has developed into a true mechanics of materials on the material manifold. This synthesis, that essentially combines Kröner's ideas and those of his contemporary, J. D. Eshelby, yields a powerful unification of some of the most fruitful developments of continuum thermomechanics at the end of the XXth century and the beginning of the XXIst. In particular, a general theory of material inhomogeneities emerges which includes the study of the progress, under the action of well defined driving forces, of many microscopic and macroscopic defects or field singularities. In particular, we emphasize the relationship between the notion of material Eshelby stress and the notion of local structural rearrangements that are responsible for many of the macroscopically observed irreversible behaviors of solid‐like matter (e.g., anelasticity, damage, phase transitions, growth). All these phenomena take place directly on the material manifold. That is, their arena and that of the associated driving forces, also called configurational forces, or material forces, require a general setting that emphasizes this material peculiarity. This is the object of the paper in which all types of applications are also mentioned.
On the scattering of point‐generated electromagnetic waves by a perfectly conducting sphere, and related near‐field inverse problems
Authors: Athanasiadis C. , Martin P.A. , Stratis I.G. 
Published: February 2003

AbstractA spherical electromagnetic wave is scattered by a bounded perfectly conducting obstacle. A generalization of the plane‐wave optical theorem is established. For a spherical scatterer, low frequency results are obtained by approximating the known exact solution (separation of variables). In particular, a closed‐form approximation of the scattered wavefield at the source of the incident spherical wave is obtained. This leads to the solution of a near‐field inverse problem, where both the source and coincident receiver are located at several points in the vicinity of a small sphere. The same inverse problem is also treated from the knowledge of the leading order term in the low‐frequency asymptotic expansion of the scattering cross‐section.
tert‐Butylphosphonic Acid: From the Bulk to the Gas Phase
Authors: Mehring Michael , Schürmann Markus , Ludwig Ralf 
Published: February 2003

AbstractThe structure of tert‐butylphosphonic acid in the solid, in solution, and in the gas phase was studied by single‐crystal X‐ray diffraction, 1H and 31P NMR spectroscopic studies in solution, solid‐state 31P NMR spectroscopy, and electrospray ionization mass spectrometry. In addition, density functional theory (DFT) calculations at the B3LYP/6‐31G*, B3LYP/6‐31+G*, and B3LYP/6‐311+G* level of theory for a large number of H‐bonded aggregates of the type (tBuPO3H2)n (Cn, Pn; n=1–7) support the experimental work. Crystallization of tBuPO3H2 from polar solvents such as CH3CN or THF gives the H‐bonded one‐dimensional polymer 2, whereas crystallization from the less polar solvent CDCl3 favors the formation of the H‐bonded cluster (tBuPO3H2)6⋅CDCl3 (1). In CDCl3 the hexamer (tBuPO3H2)6 (C6) is replaced by smaller aggregates down to the monomer with decreasing concentration. DFT calculations and natural bond orbital (NBO) analyses for the clusters C1–C7 and the linear arrays P1–P7 reveal the hexamer C6 to be the energetically favored structure resulting from cooperative strengthening of the hydrogen bonds in the H‐bonded framework. However, the average hydrogen bond strengths calculated for C6 and P2 do not differ significantly (42–43 kJ mol−1). The average distances rO⋅⋅⋅O, rOH, rPO, and rPOH in C1–C7 and P1–P7 are closely related to the hydrogen bond strength. Electrospray ionization mass spectrometry shows the presence of different anionic species of the type [(tBuPO3H2)n‐H]− (A1–A7, n=1–7) depending on the instrumental conditions. DFT calculations at the B3LYP/6‐31G* level of theory were carried out for A1–A6. We suggest the dimer [(tBuPO3H2)2‐H]− (A2) and the trimer [(tBuPO3H2)3‐H]− (A3) are the energetically favored anionic structures. A hydrogen bond energy of approximately 83 kJ mol−1 was calculated for A2. Electrospray ionization mass spectrometry is not suitable to study the assembling process of neutral H‐bonded tert‐butylphosphonic acid since the removal of a proton from the neutral aggregates has a large influence on the hydrogen bond strength and the cluster structure.
Ionische Flüssigkeiten: Innovative Lösungsmittel für die Zweiphasenkatalyse
Authors: Wasserscheid Peter 
Published: February 2003

AbstractIonische Flüssigkeiten sind bei niedrigen Temperaturen schmelzende Salze, die eine neuartige Klasse von Lösungsmitteln mit nichtmolekularem, ionischem Charakter darstellen. Durch unterschiedliche Kation/Anion‐Kombinationen können Flüssigkeiten mit sehr unterschiedlichen physikalischen und chemischen Eigenschaften erhalten werden. Durch eine gezielte Auswahl kann das ionische Medium auf die geplante Anwendung hin optimiert werden. Ionische Flüssigkeiten sind als alternative Lösungsmittel für katalytische Reaktionen aus vielen Gründen interessant: Ihre nichtflüchtige Natur bietet verfahrenstechnische Vorteile und ihre außergewöhnlichen Löslichkeitseigenschaften erlauben neue Anwendungen der Zweiphasenkatalyse.
The Use of Optical Fiber Bundles Combined with Electrochemistry for Chemical Imaging
Authors: Szunerits Sabine , Walt David R. 
Published: February 2003

AbstractThe present Review describes the progress made in using imaging optical fiber bundles for fluorescence and electrochemical‐initiated chemiluminescence imaging. A novel optoelectrochemical micro‐ring array has been fabricated and demonstrated for concurrent electrochemical and optical measurements. The device comprises optical fibers coated with gold via electroless gold deposition and assembled in a random array format. The design yielded an array of approximately 200 micro‐ring electrodes, where interdiffusional problems were minimized. The inner diameter of the ring electrode is fixed by the diameter of the individual optical fibers (25 μm), while the outer radius is determined by the thickness of the deposited gold. While all the fibers are optically addressable, they are not all electrochemically addressable. The resolution of this device is in the tens of micrometers range, determined by the diameter of the optical fiber (25 μm) and by the spacing between each electrically connected fiber. For the purpose of having well‐behaved microelectrode characteristics, this spacing was designed to be larger than 60 μm. The array was characterized using ferrocyanide in aqueous solution as a model electroactive species to demonstrate that this microelectrode array format exhibits steady‐state currents at short response times. This device has potential application to be used as an optoelectronic sensor, especially for the electrolytic generation and transmission of electrochemiluminescence, and was used to demonstrate that electrochemically generated luminescent products can be detected with the fiber assembly.
On the kinetics of the autoxidation of fats: influence of pro‐oxidants, antioxidants and synergists
Authors: Brimberg Ulla I. , Kamal‐Eldin Afaf 
Published: February 2003

AbstractThe influence of minor amounts of pro‐ and anti‐oxidants on the kinetics of the autoxidation of fat has been evaluated. The reaction rates of oxygen with the substrates were found to follow the same basic equation, hitherto established for pure substrates. There is evidence that the surface of the reaction vessel also acts as a reaction catalyst and its effect is proportional to the area of glass in contact with lipids. Oxidation is enhanced by trace metal ions as well as by surface‐active compounds (e.g. hydroperoxides and sterols). Antioxidants such as α‐tocopherol and butylated hydroxyanisole inhibit the oxidation by delaying the start of oxygen consumption (the induction period) while retarders like amino acids only decrease the rate of oxidation. Thus pro‐ and anti‐ oxidants affect either the start or the rate of oxygen consumption. The empirical formula dx/dt = k [O2] (1‐x/n) f′(t) was found applicable to the different stages of oxidation.