bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lipidic Membranes Are Potential “Catalysts” in the Ligand Activity of the Multifunctional Pentapeptide Neokyotorphin
Authors: Lopes Sílvia C. D. N. , Fedorov Aleksander , Castanho Miguel A. R. B. 
Published: March 2005

AbstractNeokyotorphin (NKT) is a multifunctional pentapeptide that is involved in biological functions as diverse as analgesia, antihibernatic regulation and proliferation stimulus of tumour cells. The interaction of neokyotorphin with cell membranes is potentially important to all these multiple biological processes since receptor‐mediated processes are thought to be involved in neokyotorphin action. Sargent and Schwyzer proposed in their “membrane catalysis” model that ligands interact with membrane lipids in order to adopt the necessary conformation for cell receptors. We have used fluorescence techniques to study the depth, orientation and extent of incorporation of NKT with model membrane systems (lipidic vesicles). The roles of lipid charge, membrane phase and sterol presence were investigated. The phenolic ring of tyrosine is located in a shallow position in membranes. The extent of partition is less in gel crystalline membranes than in liquid crystalline membranes. Addition of cholesterol causes a reorientation of the tyrosine ring at the interface of lipidic bilayers. Lipidic membranes meet all the conditions required for acting as potential “catalysts” in the ligand activity of the multifunctional pentapeptide NKT, because they modulate the exposure and orientation of the phenolic ring, which is most likely involved in docking to receptors.
Process Intensification by Miniaturization
Authors: Charpentier J.‐C. 
Published: March 2005

AbstractThe progress of basic research in chemical engineering has led to a better understanding of elementary phenomena, and it is now possible to imagine new operating modes of equipment or design novel equipment based on scientific principles. Process intensification refers to complex technologies that replace large, expensive, energy‐intensive equipment or processes with smaller, less costly, more efficient plants, or plants that combine multiple operations into a single apparatus or into fewer devices.
Design of a New Micromixer for Instant Mixing Based on the Collision of Micro Segments
Authors: Nagasawa H. , Aoki N. , Mae K. 
Published: March 2005

AbstractA new type of micromixer for rapid mixing was developed based on mixing by both kinetic energy and molecular diffusion of fluids. The rapid mixing was realized by the collision of micro segments, which were divided into several streams in the radial, at the center of the mixer. The excellent performance of the developed micromixer was confirmed by examining the Villermaux/Dushman reaction and the precipitation of polymer particles by phase separation. From these results, it was clarified that the rapid mixing was driven by both the breaking of micro segments under a high shear rate and instant molecular diffusion between micro segments. In addition, the mixer had a high throughput and corresponded to a wide range of flow rate ratios of fluids. Thus, it is expected that the proposed design concept for micro mixing will give us an efficient micro processing route in the future.
Mixing and Organic Chemistry
Authors: Bayer T. , Himmler K. 
Published: March 2005

AbstractMixing is an important unit operation in the chemical industry. Beside stirred vessels, other mixing devices like static mixers are commonly used today. Over the past years, however, microtechnology has become increasingly important for the optimization of existing and the development of new processes. Especially in chemical engineering, microstructured mixers and heat exchangers have been used to determine the potential of chemical reactions without mass or heat transfer limitations. A lot of different materials and functions are available for microstructured components. First examples of applying such components on an industrial scale have been published. This article describes the potential of microtechnology for chemical process development and presents examples from research, development and production.
Versatile Gas/Liquid Microreactors for Industry
Authors: Chambers R. D. , Fox M. A. , Holling D. , Nakano T. , Okazoe T. , Sandford G. 
Published: March 2005

AbstractThe design, fabrication, use and scale‐out of versatile, multi‐channel gas/liquid microreactors, which are suitable for both laboratory and industrial syntheses, are described. Direct fluorination reactions of diethyl malonate and Meldrum's acid using the new microreactor technology were studied to demonstrate the viability of the device for carrying out gas/liquid processes, particularly when using potentially hazardous materials.
The Application of Microreactors for Small Scale Organic Synthesis
Authors: Watts P. , Haswell S. J. 
Published: March 2005

AbstractThis review article describes how microreactors are being applied to synthetic organic chemistry within the pharmaceutical industry and how microreactors may improve the efficiency of the drug discovery process. This article explores how miniaturization may revolutionize chemical synthesis and demonstrates that products are generated in higher yield and purity compared to the equivalent bulk reactions, in much shorter periods of time.
Microreactor Technology: A Revolution for the Fine Chemical and Pharmaceutical Industries?
Authors: Roberge D. M. , Ducry L. , Bieler N. , Cretton P. , Zimmermann B. 
Published: March 2005

Abstract50 % of reactions in the fine chemical/pharmaceutical industry could benefit from a continuous process based mainly on microreactor technology. However, the frequent presence of a solid phase still hinders the widespread application of such a technology as a multi‐purpose solution. For small scale and pilot productions, speed in process R&D, as well as the avoidance of scale‐up issues, are the main drivers. On the other hand, for large scale productions, a gain in yield and safety are the main motivations for the use of micoreactor technology. The gain in yield must be significant in order to cope with the increase in capital expenditure associated with the development of a new technology.
Laminar Flow and Heat Transfer in a Periodic Serpentine Channel
Authors: Rosaguti N. R. , Fletcher D. F. , Haynes B. S. 
Published: March 2005

AbstractThe fully developed laminar flow and heat transfer behavior in periodic serpentine circular‐section channels has been studied using computational fluid dynamics (CFD). The serpentine elements are characterised by their wavelength (2 L), channel diameter (d), and radius of curvature of bends (Rc) and results are reported for (3 < L/d < 12.5, 0.525 < Rc/d < 2.25) and Reynolds numbers up to 200. The flow is characterised by the formation of a single pair of Dean vortices after each bend, these being stronger if the bend is in the same direction as the previous bend. The vortices decay downstream of the bends, but, as the Reynolds number is increased, the flow space is increasingly dominated by these vortices. At higher values of Reynolds number (corresponding to a Dean number of about 150), a second pair of vortices develops. For Re > ∼ 200, the flow becomes unsteady. Constant wall heat flux (H2) and constant wall temperature (T) boundary conditions have been examined for a range of fluid Prandtl number (0.7 < Pr < 100). The formation of Dean vortices produces significant heat transfer enhancement relative to flow in a straight pipe, with the effect being greater at higher values of Pr. Pressure drop is also increased but to a lesser extent. The alignment of the flow with the vorticity in these structures allows significant mixing of the fluid without creating large pressure‐drop penalties. Dean vortices are also found to inhibit flow separation. These results suggest an effective method for enhancement of heat transfer in deep laminar flows.
New Scopes in Process Design using Microstructured Devices
Authors: Kirschneck D. , Kober M. , Marr R. 
Published: March 2005

AbstractMicroreaction technology offers new opportunities, especially for the production of fine and other speciality chemicals. The area of process design, however, has not been widely reported in literature. Therefore, the aim of the current paper is to give an insight into the necessary steps of industrial process design in microchemical engineering.
Multicomponent Domino Processes Based on the Organocatalytic Generation of Conjugated Acetylides: Efficient Synthetic Manifolds for Diversity‐Oriented Molecular Construction
Authors: Tejedor David , González‐Cruz David , Santos‐Expósito Alicia , Marrero‐Tellado Jose Juan , de Armas Pedro , García‐Tellado Fernando 
Published: March 2005

AbstractThe organocatalytic generation of a strong base by the action of a good nucleophile is the base for the in situ catalytic generation of conjugated acetylides in the presence of aldehydes or activated ketones. The method is affordable in a multicomponent, domino format able to generate a chemically diverse set of multifunctionalized adducts that are very well suited for diversity‐oriented molecular construction. The domino process involves a nucleophile as catalyst and a terminal conjugated alkyne (HCCZ) and an aldehyde or activated ketone as building blocks. The chemical outcome of this process changes dramatically as a function of the nucleophile (tertiary amine or phosphine), temperature, stoichiometry, and solvent. These multicomponent domino processes achieve molecular construction with good atom economy and, very importantly, with an exquisite chemo‐differentiating incorporation of identical starting units into the products (nondegenerated chemical output). These properties convert the HCCZ unit into a specific building block for diversity‐oriented molecular construction. Applications to the modular and diversity‐oriented synthesis of relevant heterocycles are discussed. A protocol involving two coupled domino processes linked in a one‐pot manner will be discussed as an efficient synthetic manifold for the modular and diversity‐oriented construction of multisubstituted nitrogen‐containing heterocycles.
A calculation method of field current of synchronous machines at sudden short‐circuit
Authors: Kano Takashi , Yamamoto Shu , Ara Takahiro 
Published: March 2005

AbstractThe mutual leakage reactance between D‐axis damper and field windings is ignored in conventional D‐axis equivalent circuits. It has been pointed out, however, that the calculated value of the field current differs considerably from the measured value if this reactance is not taken into account. This is due to the difficulty of determining the physically correct damper winding impedance value. A method of determining the equivalent circuit constants using the mutual leakage reactance has been reported previously, where the D‐axis damper winding time constant is measured from the upper and lower envelopes of field current at sudden three‐phase short‐circuit. Yet there are machines for which the upper and lower envelopes of field current are not readily established, and in this case the method is unsatisfactory. The authors describe a method to accurately identify the equivalent circuit constants taking into account the mutual leakage reactance, using a standstill test with a small‐capacity DC power supply (DC decay testing method). The field current at sudden short‐circuit can be simulated accurately using these equivalent circuit constants. The validity of the proposed method is demonstrated by implementation results on two salient‐pole synchronous machines at the same specifications (one with damper winding, the other without). Furthermore, the dependent relation between the armature leakage reactance and mutual leakage reactance, as well as its influence on the calculation of field transient currents, are made clear. © 2005 Wiley Periodicals, Inc. Electr Eng Jpn, 151(3): 61–70, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20113
The non‐receptor tyrosine kinase Syk regulates lamellipodium formation and site‐directed migration of human leukocytes
Authors: Schymeinsky Jürgen , Then Cornelia , Walzog Barbara 
Published: March 2005

AbstractThe tyrosine kinase Syk is associated with CD18, the β‐subunit of the leukocyte adhesion molecules of the β2 integrin family (CD11/CD18), and becomes activated upon β2 integrin‐mediated adhesion. In this study, we elucidated the role of Syk in polarization and site‐directed migration of neutrophil‐like differentiated HL‐60 cells and monocytic THP‐1 cells. By means of confocal microscopy, we detected a homogenous distribution of Syk in unstimulated cells in suspension. The stimulation of HL‐60 cells by formyl‐methionyl‐leucyl‐phenylalanine (fMLP, 100 nM) or the activation of THP‐1 cells by monocyte chemoattractant protein‐1 (10 ng/ml) induced β2 integrin‐mediated cell adhesion and polarization on immobilized fibrinogen which was associated with an enrichment of Syk at the lamellipodium forming site. This effect was abolished by function blocking anti‐CD18 antibody or by treatment of the cells with the Syk inhibitor piceatannol (30 μM) suggesting that the redistribution of Syk required both, β2 integrin‐mediated adhesion and Syk activation. Moreover, the inhibition of Syk by piceatannol or the downregulation of Syk by antisense technique resulted in an excessive formation of lamellipodia indicating that Syk may act as a negative regulator that limits lamellipodium formation. The analysis of chemotaxis revealed that the inhibition of Syk impaired the ability of the cells to follow a chemotactic gradient whereas random migration was intact. Taken together, our data suggest a novel role for Syk in the maintenance of a bipolar phenotype by regulating lamellipodium formation, which is a critical prerequisite for site‐directed migration of leukocytes. © 2005 Wiley‐Liss, Inc.
Functional analysis of TMLH variants and definition of domains required for catalytic activity and mitochondrial targeting
Authors: Monfregola Jlenia , Cevenini Armando , Terracciano Antonio , Vlies Naomi van , Arbucci Salvatore , Wanders Ronald J.A. , D'Urso Michele , Vaz Frédéric M. , Ursini Matilde Valeria 
Published: March 2005

Abstractε‐N‐Trimethyllysine hydroxylase (TMLH) (EC 1.14.11.8) is a non‐heme‐ferrous iron hydroxylase, Fe++ and 2‐oxoglutarate (2OG) dependent, catalyzing the first of four enzymatic reactions of the highly conserved carnitine biosynthetic pathway. Otherwise from all the other enzymes of carnitine biosynthesis, TMLH was found to be associated to the mitochondrial fraction. We here report molecular cloning of two alternative spliced forms of TMLH, which appear ubiquitously expressed in human adult and fetal tissues. The deduced proteins are designated TMLH‐a and TMLH‐b, and contain 421 and 399 amino acids, respectively. They share the first N‐terminal 332 amino acids, including a mitochondrial targeting signal, but diverge at the C‐terminal end. TMLH‐a and TMLH‐b exogenous expression in COS‐1 cells shows that the first 15 amino acids are necessary and sufficient for mitochondrial import. Furthermore, comparative evolutionary analysis of the C‐terminal portion of TMLH‐a identifies a conserved domain characterized by a key triad of residues, His242‐Glu244‐His389 predicted to bind 2OG end. This sequence is conserved in the TMLH enzyme from all species but is partially substituted by a unique sequence in the TMLH‐b variant. Indeed, TMLH‐b is not functional by itself as well as a TMLH‐H389L mutant produced by site directed mutagenesis. As great interest, we found that TMLH‐b and TMLH‐H389L, individually co‐expressed with TMLH‐a in COS‐1 cells, negatively affect TMLH activity. Therefore, our studies on the TMLH alternative form provide relevant novel information, first that the C‐terminal region of TMLH contains the main determinants for its enzymatic activity including a key H389 residue, and second that TMLH‐b could act as a crucial physiological negative regulator of TMLH. © 2005 Wiley‐Liss, Inc.
Development and resolution of experimental colitis in mice with targeted deletion of dipeptidyl peptidase IV
Authors: Geier Mark S. , Tenikoff Danik , Yazbeck Roger , McCaughan Geoffrey W. , Abbott Catherine A. , Howarth Gordon S. 
Published: March 2005

AbstractGlucagon‐like peptide‐2 (GLP‐2) is a potent intestinotrophic growth factor that enhances repair of damaged intestinal tissue. However, its bioactivity is limited by dipeptidyl peptidase IV (DPIV)‐mediated degradation. We hypothesized that DPIV−/− mice would display an increased resistance to, and an enhanced recovery from, dextran sulfate sodium (DSS)‐induced colitis compared to DPIV+/+ mice. DPIV+/+ and DPIV−/− mice consumed 2% DSS for 6 days, followed by a 15 day recovery period. Mice were killed at days 0, 3, 6, 9, 14, and 21 (n = 6–8) and the small intestine and colon removed for histological assessment of villus height, crypt depth, and crypt area. The epithelial cell proliferative labeling index was determined by proliferating cell nuclear antigen (PCNA) immunostaining. Small intestine, colon, and total body weight did not differ between DPIV+/+ and DPIV−/− mice. Distal colon crypt depth did not differ significantly between DPIV+/+ and DPIV−/− mice during the development of DSS‐colitis or during the recovery phase. Similarly no significant effects were apparent on distal colon crypt area or PCNA labeling index between DPIV+/+ and DPIV−/− during the development of and recovery from DSS‐colitis. However, DPIV−/− mice still possessed significant levels of plasma DPIV‐like activity. We conclude that loss of DPIV activity does not increase resistance to experimental colitis and hypothesize that other DPIV family members may also be involved in the cleavage of GLP‐2. © 2005 Wiley‐Liss, Inc.
Investigation of adsorption of lead, mercury and nickel from aqueous solutions onto carbon aerogel
Authors: Goel Jyotsna , Kadirvelu K , Rajagopal Chitra , Garg Vinod Kumar 
Published: March 2005

AbstractRecently a new form of activated carbon has appeared: carbon aerogel (CA). Its use for the removal of inorganic (and especially metal ions) has not been studied. In the present study, the adsorption of three metal ions, Hg(II), Pb(II) and Ni(II), onto carbon aerogel has been investigated. Batch experiments were carried out to assess adsorption equilibria and kinetic behaviour of heavy metal ions by varying parameters such as agitation time, metal ions' concentration, adsorbent dose and pH. They facilitated the computation of kinetic parameters and maximum metal ion adsorption capacities. Increasing the initial solution pH (2–10) and carbon concentration (50–500 mg per 50 cm3) increases the removal of all three metal ions. A decrease of equilibrium pH with an increase of metal ion concentration led us to propose an adsorption mechanism by ion exchange between metal cations and H+ at the carbon aerogel surface. Carboxylic groups are especially involved in this adsorption mechanism. Langmuir and Freundlich isotherm models were used to analyse the experimental data of carbon aerogel. The thermodynamics of the metal adsorption was also investigated for the practical implementation of the adsorbent. The sorption showed significant increase with increase of temperature. Kinetics models describing the adsorption of Hg(II), Pb(II) and Ni(II) ions onto carbon aerogel have been compared. Kinetics models evaluated include the pseudo‐first order and second order model. The parameters of the adsorption rate constants have been determined and the effectiveness of each model assessed. The result obtained showed that the pseudo‐second order kinetic model correlated well with the experimental data and better than the pseudo‐first order model examined in the study. Mass transfer coefficients obtained can be useful in designing wastewater treatment systems or in the development of environmental technologies. Copyright © 2005 Society of Chemical Industry
Analysis and simulation of the sludge profile dynamics in a full‐scale clarifier
Authors: De Clercq Jeriffa , Devisscher Martijn , Boonen Ivo , Defrancq Jacques , Vanrolleghem Peter A 
Published: March 2005

AbstractA one‐dimensional clarifier model was assessed for its capability to describe dynamic full‐scale sludge concentration profiles by using the settling properties calibrated with batch settling curve data collected by a SettloMeter®. These sludge concentration profiles and batch settling tests formed part of a detailed one‐month measuring campaign on a full‐scale wastewater treatment plant; the measurements showed a daily variation in settling properties. Using the settling properties obtained from batch settling tests and a one‐dimensional model without dispersion, the dynamics of the full‐scale clarifier were analysed and the need for dispersion clearly shown. The parameters of the dispersion model were estimated from the full‐scale sludge concentration profiles. The settling properties of activated sludge can be automatically determined by fitting the model to the on‐line batch settling curve measurements and are needed as input to the one‐dimensional model. This model can therefore be used for operation and control. The dispersion model parameters have to be determined from dynamic sludge concentration profiles but are assumed to be constant for a specific clarifier. Copyright © 2005 Society of Chemical Industry
Enhancement of enantioselectivity and reaction rate on the synthesis of (S)‐ketoprofen hydroxyalkyl ester in organic solvents via isopropanol‐dried immobilized lipase
Authors: Chang Chun‐Sheng , Hsu Chin‐Shuo 
Published: March 2005

AbstractLipase‐catalyzed enantioselective esterification between (R,S)‐ketoprofen and alkanediol in organic solvents was developed to produce (S)‐ketoprofen hydroxyalkyl esters. The acyl acceptor of 1,6‐hexanediol for the resolution of (R,S)‐ketoprofen yielded only the enantioselectivity (the enantiomeric ratio of initial rate for (S)‐ketoprofen to that of (R)‐ketoprofen) VS/VR = 8, when crude Lipase MY originating from Candida rugosa was used. However, isopropanol‐dried immobilized lipases (IPA‐dried IM‐lipase) effectively enhanced the enantioselectivity to greater than 20 in the esterification of (R,S)‐ketoprofen when 1,4‐butanediol, 1,5‐pentanediol or 1,6‐hexanediol was employed. IPA‐dried IM‐lipase and isooctane were selected to use for optimally immobilized lipase and reaction medium, respectively. The IPA‐dried IM‐lipase exhibited the highest enantioselectivity, E = 26.7, to the (S)‐enantiomer with 1,5‐pentanediol and the best enzyme activity to the (S)‐enantiomer with 1,4‐butanediol. The finding indicates that the carbon chain length of the alkanediol strongly affected the enzyme activity and enantioselectivity of lipase‐catalyzed esterification. A maximum enantioselectivity of 37 at 27 °C was generated by IPA‐dried IM‐lipase for the enantioselective esterification of racemic ketoprofen with 1,4‐butanediol. IPA‐dried IM‐lipase can effectively increase the enantioselectivity of lipase. Copyright © 2005 Society of Chemical Industry