bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of organic and inorganic polyamine cations on the structure of human serum albumin
Authors: Ouameur A. Ahmed , Mangier E. , Diamantoglou S. , Rouillon R. , Carpentier R. , Tajmir‐Riahi H. A.
Published: February 2004

The presence of several high affinity binding sites on human serum albumin (HSA) makes it a possible target for many organic and inorganic molecules. Organic polyamines are widely distributed in living cells and their biological roles have been associated with their physical and chemical interactions with proteins, nucleic acids, and lipids. This study is designed to examine the effects of spermine, spermidine, putrescine, and cobalt [Co(III)]–hexamine cations on the solution structure of HSA using Fourier transform IR, UV–visible, and circular dichroism (CD) spectroscopic methods. The spectroscopic results show that polyamine cations are located along the polypeptide chains with no specific interaction. The order of perturbations is associated with the number of positive charges of the polyamine cation: spermine > Co(III)–hexamine > spermidine > putrescine. The overall binding constants are 1.7 × 104, 1.1 × 104, 5.4 × 103, and 3.9 × 103M−1, respectively. The protein conformation is altered (IR and CD data) with reductions of α helices from 60 to 55% for free HSA to 50–40% and with increases of β structures from 22 to 15% for free HSA to 33–23% in the presence of polyamine cations. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Incorporation of anthraquinonyl group into λ‐Cro repressor protein for strand‐ and position‐specific photocleavage of double‐stranded DNA
Authors: Sasaki Hiroshi , Ikeda Kazumasa , Suzuki Maya , Ninomiya Keiko , Sisido Masahiko
Published: February 2004

λ‐Cro repressor protein incorporated with a 2‐anthraquinonylalanine (anqAla) at the 64th position was chemically synthesized by solid‐phase method. The 64th position was selected according to previous information on various mutants of Cro incorporated with a single anqAla unit, that were synthesized through an Escherichia coli in vitro protein‐synthesizing system. The 64anqAla mutant bound to a dsDNA of consensus operator sequence and underwent strand‐ and position‐specific photocleavage of the dsDNA at the GG sequence after treatment with piperidine. The mutant also underwent position‐specific self‐photoscission. The self‐photoscission was retarded in the presence of the dsDNA. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci) , 2004
Multifunctional peptide fibrils for biomedical materials
Authors: Kasai Shingo , Ohga Yukiko , Mochizuki Mayumi , Nishi Norio , Kadoya Yuichi , Nomizu Motoyoshi
Published: February 2004

The Ile‐Lys‐Val‐Ala‐Val (IKVAV) containing peptide, A208 (AASIKVAVSADR, mouse laminin α1 chain 2097–2108), was recently found to form amyloid‐like fibrils. Fibril formation is critical for its biological activities, including promotion of cell adhesion and neurite outgrowth. In the present study, we designed multifunctional peptide fibrils using the A208 peptide and an Arg‐Gly‐Asp (RGD)‐containing fibronectin active sequence for biomedical applications. The fibronectin active sequence GRGDS (FN) or a scrambled sequence RSGGD (SC) were conjugated to either A208 or to A208S (AASVVIAKSADR), a scrambled peptide of A208, with a glycine as a spacer. The FN‐A208 and SC‐A208 peptides formed a gel and were stained with Congo red similar to that of A208, but FN‐A208S and SC‐A208S did not form a gel. These results indicate that FN‐A208 and SC‐A208 form amyloid‐like fibrils similar to A208. A208 and SC‐A208 promoted cell attachment with filopodia formation, and this adhesion was inhibited by the IKVAV‐containing peptide, but not by EDTA or a GRGDS peptide. FN‐A208 promoted cell attachment with well‐organized actin stress fibers, and this adhesion was partially inhibited by either EDTA, GRGDS, or IKVAV. These data suggest that A208 binds to only IKVAV receptor(s) while the FN‐A208 interacts with both integrins and the IKVAV receptor(s). We conclude that multifunctional peptide fibrils can be designed by conjugation of active peptides on A208 and that this construct has potential to serve as a bioadhesive for tissue regeneration and engineering. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2004
Mechanical force analysis of peptide interactions using atomic force microscopy
Authors: Nakamura Chikashi , Takeda Seiji , Kageshima Masami , Ito Miyuki , Sugimoto Naoki , Sekizawa Kazuko , Miyake Jun
Published: February 2004

Some peptides have previously been reported to bind low molecular weight chemicals. One such peptide with the amino acid sequence His–Ala–Ser–Tyr–Ser was selectively screened from a phage library and bound to a cationic porphyrin, 5,10,15,20‐tetrakis(N‐methylpyridinium‐4‐yl)‐21H,23H‐porphine (TMpyP), with a binding constant of 105M−1(J. Kawakami, T. Kitano, and N. Sugimoto, Chemical Communications, 1999, pp. 1765–1766). The proposed binding was due to π‐electron stacking from two aromatic amino acids of histidine and tyrosine. In this study, the weak interactions between TMpyP and the peptide were further investigated by force curve analysis using atomic force microscopy (AFM). The mechanical force required to unbind the peptide–porphyrin complex was measured by vertical movement of the AFM tip. Peptide self‐assembled monolayers were formed on both a gold‐coated mica substrate and a gold‐coated AFM tip. The TMpyPs could bind between the two peptide layers when the peptide‐immobilized AFM tip contacted the peptide‐immobilized substrate in solution containing TMpyP. In the retracting process a force that ruptured the interaction between TMpyPs and peptides was observed. The unbinding force values correlated to the concentration of TMpyP. A detection limit of 100 ng/mL porphyrin was obtained for the force measurement, and was similar to surface plasmon resonance sensor detection limits. Furthermore, we calculated the product of the observed force and the length of the molecular elongation to determine the work required to unbind the complexes. The obtained values of unbinding work were in a reasonable range compared to the binding energy of porphyrin–peptide. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci) , 2004
On selectivity and sensitivity of synthetic multifunctional pores as enzyme sensors: Discrimination between ATP and ADP and comparison with biological pores
Authors: Sordé Nathalie , Matile Stefan
Published: February 2004

This report delineates scope and limitation of the selectivity of synthetic multifunctional pores as enzyme sensors using glycolytic enzymes as example (G. Das, P. Talukdar, and S. Matile, Science, 2002, Vol. 298, pp. 1600–1602). Unproblematic detectability of hexokinase and phosphofructokinase demonstrates that the selectivity of synthetic multifunctional pore (SMPs) sensors suffices to sense ATP in mixed analytes containing ADP, whereas detection of the isomerization of glucose 6‐phosphate into fructose 6‐phosphate by phosphoglucose isomerase is not possible with confidence. The sensitivity of SMP sensors is sufficient for end‐point detection of one picomole poly‐L‐glutamate hydrolyzed by papain in unoptimized assay format; the sensitivity of melittin as representative biological pore of similar charge and aggregation number to detect the same reaction is more than four orders of magnitude inferior. © 2004 Wiley Periodicals, Inc. Biopolymers (Pept Sci) , 2004
Incorporation of thioether building blocks into an αvβ3‐specific RGD peptide: Synthesis and biological activity
Authors: Kelleman Audrey , Mattern Ralph‐Heiko , Pierschbacher Michael D. , Goodman Murray
Published: February 2004

We report the design, synthesis, and binding affinities of a family of thioether analogues of the αvβ3‐specific compound c[(Mpa)RGDD(tBuG)C]‐NH2. The synthesis of the thioether building blocks is scalable and produced the desired products in good yields. The linear peptides were synthesized on solid supports, followed by cyclization in solution. Our analogues demonstrate interesting binding data to the isolated receptors. In particular, the peptide c[NH‐Arg‐Gly‐Asp‐Asp‐(tBuG)‐Cys(S‐CH2‐CO)]NH2 (1) exhibits differences in binding when compared to the parent compound and demonstrates potent affinity to the αvβ3 and α5β1 receptors while having reduced binding to the αIIbβ3 receptor. This result combined with the replacement of the disulfide with a thioether makes this compound interesting for further development. © 2003 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2003
Design and synthesis of substrate‐based inhibitors of botulinum neurotoxin type B metalloprotease
Authors: Oost Thorsten , Sukonpan Chanokporn , Brewer Matthias , Goodnough Michael , Tepp William , Johnson Eric A. , Rich Daniel H.
Published: February 2004

Botulinum toxin (BoNT) metalloproteases and related proteases are the most selective proteases known. X‐ray crystal structures suggest that the native enzymes exist in catalytically incompetent forms that must be activated by substrate binding. In order to characterize the postulated substrate‐induced conformational changes, we synthesized a series of transition state analog inhibitors (TSI) in which the dipeptide cleavage site has been replaced by tetrahedral intermediate analogs within the minimal substrate peptide sequence. Reduced amide, α‐hydroxyamide, α‐thio‐amide, and hydroxyethylamine analogs of —Gln–Phe— were incorporated via solid phase peptide synthesis into 35‐mer analogs of the minimal peptide substrate sequence. The synthesis, characterization, and inhibition kinetics for four series of compounds against holotoxin BoNT/B is described. The α‐thiol amide derivatives of the 35‐mer substrate were found to inhibit BONT/B in the low micromolar range. © 2003 Wiley Periodicals, Inc. Biopolymers (Pept Sci), 2003
1,1,1,3,3,3‐hexafluoroisopropanol induced thermal unfolding and molten globule state of bovine α‐lactalbumin: Calorimetric and spectroscopic studies
Authors: Kundu Agnita , Kishore Nand
Published: February 2004

The thermal denaturation of α‐lactalbumin was studied at pH 7.0 and 9.0 in aqueous 1,1,1,3,3,3‐hexafluoroisopropanol (HFIP) by high‐sensitivity differential scanning calorimetry. The conformation of the protein was analyzed by a combination of fluorescence and circular dichroism measurements. The most obvious effect of HFIP was lowering of the transition temperature with an increase in the concentration of the alcohol up to 0.30M, beyond which no calorimetric transition was observed. Up to 0.30M HFIP the calorimetric and van't Hoff enthalpy remained the same, indicating the validity of the two‐state approximation for the thermal unfolding of α‐lactalbumin. The quantitative thermodynamic parameters accompanying the thermal transitions have been evaluated. Spectroscopic observations confirm that α‐lactalbumin is in the molten globule state in the presence of 0.50M HFIP at pH 7.0 and 0.75M HFIP at pH 9.0. The results also demonstrate that α‐lactalbumin in the molten globule state undergoes a noncooperative thermal transition to the denatured state. It is observed that two of four tryptophans are exposed to the solvent in the HFIP induced molten globule state of α‐lactalbumin compared to four in the 8.5M urea induced denatured state of the protein. It is also observed that the HFIP induced molten globule states at the two pH values are different from the acid induced molten globule state (A state) of α‐lactalbumin. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004
Cloning, expression and characterization of recombinant sweet‐protein thaumatin II using the methylotrophic yeast Pichia pastoris
Authors: Masuda Tetsuya , Tamaki Shinobu , Kaneko Ryosuke , Wada Ritsuko , Fujita Yuki , Mehta Alka , Kitabatake Naofumi
Published: February 2004

Thaumatin, an intensely sweet‐tasting protein, was secreted by the methylotrophic yeast Pichia pastoris. The mature thaumatin II gene was directly cloned from Taq polymerase‐amplified PCR products by using TA cloning methods and fused the pPIC9K expression vector that contains Saccharomyces cerevisiae prepro α‐mating factor secretion signal. Several additional amino acid residues were introduced at both the N‐ and C‐terminal ends by genetic modification to investigate the role of the terminal end region for elicitation of sweetness in the thaumatin molecule. The secondary and tertiary structures of purified recombinant thaumatin were almost identical to those of the plant thaumatin molecule. Recombinant thaumatin II elicited a sweet taste as native plant thaumatin II; its threshold value of sweetness to humans was around 50 nM, which is the same as that of plant thaumatin II. These results demonstrate that the functional expression of thaumatin II was attained by Pichia pastoris systems and that the N‐ and C‐terminal regions of the thaumatin II molecule do not ‐play an important role in eliciting the sweet taste of thaumatin. © 2004 Wiley Periodicals, Inc.
Yeast plasma membrane Ena1p ATPase alters alkali‐cation homeostasis and confers increased salt tolerance in tobacco cultured cells
Authors: Nakayama Hideki , Yoshida Kazuya , Shinmyo Atsuhiko
Published: February 2004

In plants, the plasma membrane Na+/H+ antiporter is the only key enzyme that extrudes cytosolic Na+ and contributes to salt tolerance. But in fungi, the plasma membrane Na+/H+ antiporter and Na+‐ATPase are known to be key enzymes for salt tolerance. Saccharomyces cerevisiae Ena1p ATPase encoded by the ENA1/PMR2A gene is primarily responsible for Na+ and Li+ efflux across the plasma membrane during salt stress and for K+ efflux at high pH and high K+. To test if the yeast ATPase would improve salt tolerance in plants, we expressed a triple hemagglutinin (HA)‐tagged Ena1p (Ena1p‐3HA) in cultured tobacco (Nicotiana tabacum L.) cv Bright Yellow 2 (BY2) cells. The Ena1p‐3HA proteins were correctly localized to the plasma membrane of transgenic BY2 cells and conferred increased NaCl and LiCl tolerance to the cells. Under moderate salt stress conditions, the Ena1p‐3HA‐expressing BY2 clones accumulated lower levels of Na+ and Li+ than nonexpressing BY2 clones. Moreover, the Ena1p‐3HA expressing BY2 clones accumulated lower levels of K+ than nonexpressing cells under no‐stress conditions. These results suggest that the yeast Ena1p can also function as an alkali‐cation (Na+, Li+, and K+) ATPase and alter alkali‐cation homeostasis in plant cells. We conclude that, even with K+‐ATPase activity, Na+‐ATPase activity of the yeast Ena1p confers increased salt tolerance to plant cells during salt stress. © 2004 Wiley Periodicals, Inc.
Making sense of male rape: constructions of gender, sexuality and experience of rape victims
Authors: Doherty Kathy , Anderson Irina
Published: February 2004

This study reports a preliminary investigation into accounting practices for male rape in conversation. Thirty men and women, in dyads, were asked to discuss an incident of male rape presented to them in a vignette. The findings showed that two main issues were discussed: the experience of the rape act and societal responses to male victims. In addition, participants established a ‘hierarchy of suffering’, where rape was judged to be worse for ‘heterosexual’ men than it is for ‘women’ or ‘gay’ men. Hegemonic, phallocentric representations of heterosexuality were mobilized to argue that acts of rape and consensual intercourse are the same for ‘gay’ men and ‘women’ and therefore less traumatic than for ‘heterosexual’ men. This obscures the violence of rape for gay men and women and exonerates perpetrators by minimizing injury sustained. Participants also argued that heterosexual victims are likely to experience ridicule for having departed from hegemonic masculinity. Arguments were constructed to avoid charges of being dismissive towards women and gay men and of victim blaming in relation to heterosexual men. Copyright © 2004 John Wiley & Sons, Ltd.
Gold Glyconanoparticles as New Tools in Antiadhesive Therapy
Authors: Rojo Javier , Díaz Vicente , de la Fuente Jesús M. , Segura Inmaculada , Barrientos Africa G. , Riese Hans H. , Bernad Antonio , Penadés Soledad
Published: February 2004

Gold glyconanoparticles (GNPs) have been prepared as new multivalent tools that mimic glycosphingolipids on the cell surface. GNPs are highly soluble under physiological conditions, stable against enzymatic degradation and nontoxic. Thereby GNPs open up a novel promising multivalent platform for biological applications. It has recently been demonstrated that specific tumor‐associated carbohydrate antigens (glycosphingolipids and glycoproteins) are involved in the initial step of tumor spreading. A mouse melanoma model was selected to test glyconanoparticles as possible inhibitors of experimental lung metastasis. A carbohydrate–carbohydrate interaction is proposed as the first recognition step for this process. Glyconanoparticles presenting lactose (lacto‐GNPs) have been used successfully to significantly reduce the progression of experimental metastasis. This result shows for the first time a clear biological effect of lacto‐GNPs, demonstrating the potential application of this glyconanotechnology in biological processes.
Sequence‐specific Methyltransferase‐Induced Labeling of DNA (SMILing DNA)
Authors: Pljevaljčić Goran , Schmidt Falk , Weinhold Elmar
Published: February 2004

A new concept for sequence‐specific labeling of DNA by using chemically modified cofactors for DNA methyltransferases is presented. Replacement of the amino acid side chain of the natural cofactor S‐adenosyl‐L‐methionine with an aziridine group leads to a cofactor suitable for DNA methyltransferase‐catalyzed sequence‐specific coupling with DNA. Sequence‐specifically fluorescently labeled plasmid DNA was obtained by using the DNA methyltransferase from Thermus aquaticus (M.TaqI) as catalyst and attaching a fluorophore to the aziridine cofactor. First results suggest that all classes of DNA methyltransferases with different recognition sequences can be used. In addition, this novel method for DNA labeling should be applicable to a wide variety of reporter groups.
A Proposed Mechanism for the Reductive Ring Opening of the Cyclodiphosphate MEcPP, a Crucial Transformation in the New DXP/MEP Pathway to Isoprenoids Based on Modeling Studies and Feeding Experiments
Authors: Brandt Wolfgang , Dessoy Marco A. , Fulhorst Michael , Gao Wenyun , Zenk Meinhart H. , Wessjohann Ludger A.
Published: February 2004

Experimental and theoretical investigations concerning the second‐to‐last step of the DXP/MEP pathway in isoprenoid biosynthesis in plants are reported. The proposed intrinsic or late intermediates 4‐oxo‐DMAPP (12) and 4‐hydroxy‐DMAPP (11) were synthesized in deuterium‐ or tritium‐labeled form according to new protocols especially adapted to work without protection of the diphosphate moiety. When the labeled compounds MEcPP (7), 11, and 12 were applied to chromoplast cultures, aldehyde 12 was not incorporated. This finding is in agreement with a mechanistic and structural model of the responsible enzyme family: a three‐dimensional model of the fragment L271–A375 of the enzyme GcpE of Streptomyces coelicolor including NADPH, the Fe4S4 cluster, and MEcPP (7) as ligand has been developed based on homology modeling techniques. The model has been accepted by the Protein Data Bank (entry code 1OX2). Supported by this model, semiempirical PM3 calculations were performed to analyze the likely catalysis mechanism of the reductive ring opening of MEcPP (7), hydroxyl abstraction, and formation of HMBPP (8). The mechanism is characterized by a proton transfer (presumably from a conserved arginine 286) to the substrate, accompanied by a ring opening without high energy barriers, followed by the transfer of two electrons delivered from the Fe4S4 cluster, and finally proton transfer from a carboxylic acid side chain to the hydroxyl group to be removed from the ligand as water. The proposed mechanism is in agreement with all known experimental findings and the arrangement of the ligand within the enzyme. Thus, a very likely mechanism for the second to last step of the DXP/MEP pathway in isoprenoid biosynthesis in plants is presented. A principally similar mechanism is also expected for the reductive dehydroxylation of HMBPP (8) to IPP (9) and DMAPP (10) in the last step.
Structure–Activity Studies on the Corticotropin Releasing Factor Antagonist Astressin, leading to a Minimal Sequence necessary for Antagonistic Activity
Authors: Rijkers Dirk T. S. , Kruijtzer John A. W. , van Oostenbrugge Marja , Ronken Eric , den Hartog Jack A. J. , Liskamp Rob M. J.
Published: February 2004

Corticotropin Releasing Factor (CRF) antagonists are considered promising for treatment of stress‐related illnesses such as major depression and anxiety‐related disorders. We report here the design, synthesis and biological evaluation of 91 truncated astressin analogues in order to deduce the pharmacophoric amino acid residues. Such truncated peptides may serve as valuable lead structures for the development of new small, non‐peptide‐based CRF antagonists. N‐Terminal truncation of astressin led to active CRF antagonists that are substantially reduced in size and are selectively active at the human CRF receptor type 1 in vitro and in vivo. Subsequently, an alanine scan in combination with further truncated derivatives led to the proposal of a new pharmacophoric model of peptide‐based CRF antagonists. It was found that the astressin(27–41)C sequence is the shortest active CRF antagonist. The first eight N‐terminal amino acid residues were found to be an important structural determinant and were replaceable by alanine residues, thus enhancing the α‐helical propensity. A covalent structural constraint is of utmost importance for the preorganization of the C‐terminal amino acid residues. The C‐terminal heptapeptide sequence, however, was found to be crucial for the antagonistic activity, since substitution or deletion of any residue led to inactive compounds.
DNA Compaction by Divalent Cations: Structural Specificity Revealed by the Potentiality of Designed Quaternary Diammonium Salts
Authors: Zinchenko Anatoly A. , Sergeyev Vladimir G. , Yamabe Kuniaki , Murata Shizuaki , Yoshikawa Kenichi
Published: February 2004

DNA interaction with quaternary diammonium dications, R(CH3)2N+(CH2)nN+(CH3)2R, having various intercharge distances, lengths, and branching, and the chemical nature of the hydrophobic substituents were investigated by fluorescent microscopy and circular dichroism (CD) spectroscopy to reveal their structural specificity for binding to DNA. The conformational behavior of DNA was found to be highly sensitive to the structure of the dications with separated charges. The distance between two ammonium groups greatly influences the compaction activity of the dications. To explain this situation, we proposed a model that demonstrates that the charge density of the dication and the geometric fit between DNA phosphates and the ammonium groups in the dications play an important role in providing efficient DNA collapse. Elongation of the alkyl substituents (R) in the diammonium salts from ethyl to hexyl did not generate any significant alterations in the compaction activities, whereas the branching of substituents caused a drastic decrease in their compaction ability. Based on the results of CD spectroscopy, it was found that the ability of the dications to provoke a DNA transition from the B‐form to A‐form was also specific: it depended on their intercharge distances and was independent of the length of alkyl substituents.
Cover Picture: Site‐Specific Modification of Epstein–Barr Virus‐Encoded RNA 1 with N2‐Benzylguanosine Limits the Binding Sites Occupied by PKR (ChemBioChem 3/2004)
Authors: Puthenveetil Sujiet , Véliz Eduardo A. , Beal Peter A.
Published: February 2004

The cover picture shows the use of site‐specific incorporation of N2‐benzylguanosine into RNA as a method for controlling the binding sites occupied by proteins that contain double‐stranded RNA binding motifs (dsRBMs). A fragment of the Epstein–Barr virus‐encoded RNA 1 (EBER1) binds dsRBM I from the RNA‐dependent protein kinase (PKR) at two sites. Based on data from affinity cleavage experiments and molecular modeling, nucleotide positions were chosen in this RNA for incorporation of N2‐benzyl guanosine, which places a bulky benzyl group in the minor groove of the RNA duplex. These site‐specific modifications lead to controlled inhibition of binding by PKR at the two different sites. This simple but effective technique can be further used to study similar dsRBM–RNA complexes. Modifications of duplex RNA like this that prevent dsRBMs from binding may be necessary in the development of RNA interference reagents (siRNAs) that will not interact with PKR or other double‐stranded RNA binding proteins. For more details see the article by P. A. Beal et al. on p. 383 ff.
LDA‐Measurements in a Stirred Tank With a Liquid‐Liquid System at High Volume Percentage Dispersed Phase
Authors: Svensson F.J.E. , Rasmuson A.
Published: February 2004

The purpose of this study is to evaluate how the flow is influenced by the volume percentage of dispersed phase in a liquid‐liquid system. A novel model system consisting of two refraction index matched immiscible liquids is presented along with experimental velocity vector fields of the continuous phase that utilises the non‐intrusive Laser‐Doppler‐Anemometry technique. Three velocity components have been measured inside a baffled cylindrical tank, stirred with a six‐bladed Rushton‐impeller. The experiments show that the vortex below the impeller is stretched, primarily in the radial direction, with increasing dispersed phase content. A small change in the shape of the vortex above the impeller can also be observed. The turbulence is dampened with increasing dispersed volume fraction.
Mixing Studies Related to the Cleaning of Molten Aluminium
Authors: Kimata M. , Nayan N. , Bujalski W. , Nienow Alvin W. , Song J.L. , Jolly M.R.
Published: February 2004

Molten aluminium is traditionally “cleaned” by a chlorine‐based fluxing gas. This gas also has to provide the motive power for mixing. Recently, mechanical agitation with solid fluxes has been considered as a replacement for environmental reasons. Here, these two methods of mixing are compared using particle image velocimetry (PIV), decolourisation for homogenisation and power measurement for comparison of efficiencies. A geometrically scaled‐down vessel was used, with air to mimic “chlorine” fluxing and with water as the working fluid. At equivalent mean specific energy dissipation rates, $ \bar \varepsilon $T, maximum velocities are higher and mixing times are shorter with an impeller. This improved performance is achieved with the impeller without causing surface gas entrainment, the latter being detrimental to fluxing.
CFD Modeling of Turbulent Jacket Heat Transfer in a Rushton Turbine Stirred Vessel
Authors: Zakrzewska B. , Jaworski Z.
Published: February 2004

CFD modelling of the turbulent heat transfer was performed for a stirred tank equipped with a Rushton turbine impeller and four standard baffles. Eight different turbulence models, i.e. the standard k‐ϵ, RNG k‐ϵ, realizable k‐ϵ, Chen‐Kim k‐ϵ, optimized Chen‐Kim k‐ϵ, standard k‐ω, k‐ω SST and Reynolds stress models, were used during the modelling. In all investigated cases, the boundary flow at the vessel wall was described by the standard logarithmic wall functions. The CFD modelling values of the local heat transfer coefficient were compared with the corresponding experimental data. The best agreement was obtained for the standard k‐ϵ, optimized Chen‐Kim k‐ϵ and k‐ω SST models.
Gas Flow Behavior in a Two‐Phase Reactor Stirred with Triple Turbines
Authors: Majirova H. , Pinelli D. , Machon V. , Magelli F.
Published: February 2004

Gas behavior was studied in a gas‐liquid reactor stirred with multiple turbines. Triple PBTs pumping either down or up and BT‐6's were used. The behavior of coalescing (water) and non‐coalescing (sodium sulfate solution) systems was investigated. The gas phase behavior was characterized by means of the RTD and modeled with the axial dispersion model. This model was confirmed to interpret the experimental data well for water and satisfactorily for the coalescence‐inhibiting solutions. The influence of the operating conditions, turbine type and system coalescing behavior on the model parameters is discussed. Comparison is also made with similar data regarding Rushton turbines and high‐solidity ratio hydrofoils, as well as gas holdup.
Design of Horizontal Vessels Operated as CSTR – Basic Mixing Tasks, RTD, Productivity
Authors: Forschner P. , Houlton D. , Kassera V. , Klepper R. , Krebs R.
Published: February 2004

Agitator performance in standard vertical vessels with cylindrical shape, dished bottom and zero to four baffles has been the topic of numerous publications. In certain industries, however, horizontal cylindrical vessels with hemispherical ends, divided internally into multiple compartments, are preferred for continuous processes operating at high pressures. Use of standard correlations derived from vertical vessels may lead to incorrect performance predictions for these horizontal vessels, and hence unsatisfactory process results. A number of laboratory trials were undertaken to identify differences in behavior and potential means to improve design for horizontal vessels. Differences with respect to solids suspension, mixing time and residence time distribution were studied. CFD simulations were undertaken and validated against the experimental results.
Mixing in Sub‐micron Ducts
Authors: Nauman E.B. , Nigam A.
Published: February 2004

This paper considers a class of fluidic devices, anticipated to become important in the near future, where characteristic channel dimensions are in the range 0.1 to 1.0 microns. Typical current applications of microfluidics have device sizes of 10 to 100 micron, this is sufficiently small to force laminar flow but not so small that molecular diffusion is a dominant factor. In the smaller devices contemplated here, diffusion is important and existing mixing strategies and correlations are no longer applicable. Novel results and interesting complexities are discussed for reactive, single and two phase flows in sub‐micron channels.
Effects of Fine Scale Turbulent Flow and Mixing in Agglomerative Precipitation
Authors: Bałdyga J. , Jasińska M. , Krasiński A. , Rožeń A.
Published: February 2004

Precipitation of a solid product from aqueous ionic solutions, including mixing, fast chemical reaction, nucleation, growth and agglomeration of crystals is considered. This work concentrates on the phenomenon of particle agglomeration which dominates the precipitation process at high supersaturation. Modeling of particle collision includes effects of bulk fluid motion, Brownian diffusion and colloidal forces for particles of equal and unequal size. The concept of probability of agglomeration based on multifractal formalism is introduced and applied. A simplified version of the model is linked to CFD and results of computations are compared with experimental data for barium sulfate precipitation.
A Multi‐Block Approach to Obtain Angle‐Resolved PIV Measurements of the Mean Flow and Turbulence Fields in a Stirred Vessel
Authors: Khan F.R. , Rielly C.D. , Hargrave G.K.
Published: February 2004

Two‐dimensional Particle Image Velocimetry (PIV) measurements have been used to characterize the complex turbulent flow generated by a T/3 45° pitched‐blade down‐flow turbine, operated at Re ≈ 5 · 104, in a fully turbulent stirred vessel. To maintain high spatial resolution when viewing the whole vessel, a multi‐block approach has been developed, which combines data from different fields of view into a composite flow map. Using 500 measurements of instantaneous u and v velocity fields, angle‐resolved mean velocity maps and turbulence properties, such as the RMS velocities and the turbulence kinetic energy, have been estimated near to the blade, as well as in the bulk of the vessel, at a spatial resolution of between 1 and 2 mm. Vorticity maps have also been calculated to help visualize the trailing vortex structures close to the impeller blades and integral length scales have been estimated from the two‐dimensional spatial auto‐correlation function. It is shown than the common assumption that the integral length scale is about half the blade width is an overestimate close to the impeller and an underestimate far from the impeller.
Influence of Physical Properties on Drop Size Distribution of Stirred Liquid‐Liquid Dispersions
Authors: Kraume M. , Gäbler A. , Schulze K.
Published: February 2004

An experimental investigation was carried out to analyse the influence of coalescence behavior on drop size distributions in stirred liquid‐liquid dispersions. An endoscope measurement technique was applied that allowed the determination of drop sizes even with high volumetric dispersed phase fractions φ of up to 0.5. The influence of pH and addition of ions was studied by shaking and stirring experiments. For high coalescence rates, the results show self‐similar drop size distributions independent of all other parameters. With low coalescence rates the Sauter diameter d32 decreases and the distributions become narrower. When phase ratios were increased the common correlation d32 ∼ (1 + const. φ) We–0.6 did not lead to a reliable description of the mean drop sizes due to coalescence effects.
Particle Flow Modelling in Slurry‐Fed Stirred Vessels
Authors: Scargiali F. , Grisafi F. , Cermakova J. , Machon V. , Brucato A.
Published: February 2004

Despite its importance, experimental information on the Residence Time Distribution (RTD) of solid particles in continuous‐flow stirred vessels is still scant. In this work, experimental data on particle RTD in a high‐aspect‐ratio vessel stirred by three equally‐spaced Rushton turbines, obtained by means of Twin Systems Approach (TSA), are employed to assess the suitability of the well known Axial‐Dispersion Model to describe particle behavior in the investigated system. The data analysis and model parameter assessment are preceded by a discussion on the utility of self‐recirculated systems in carrying out experiments concerning continuous slurry‐fed apparatuses. In particular, the suitability of single recirculated systems is discussed and a way to extract numerical RTD data from the relevant experiments is proposed. The advantages and disadvantages of employing instead a couple of twin systems, as it was actually done to obtain the experimental data employed in this work, is shortly discussed.
The Future of Mixing Research
Authors: Kresta Suzanne M. , Krebs R. , Martin T.
Published: February 2004

This paper is the result of a plenary discussion session held at the 11th European Conference on Mixing. Three perspectives on mixing research are explored: that of the industrialist, the equipment manufacturer, and the academic researcher. There was strong agreement that, while the one dimensional problems are reasonably well understood and many engineers thus perceive that mixing is simple, current practice actually requires us to address complex, multi‐dimensional problems with interactions between mixing, reaction, multi‐phase physics, surface phenomena, and transport phenomena. Understanding these multi‐scale, multi‐mechanism problems requires models which include interactions between the phenomena, and allow the effects of these interactions to emerge. Developing these models will require us to shift our perspective on mixing from one of equipment design to one of the mixing field as a fundamental physical mechanism.
Halbempirische Gleichungen für die Verweilzeitverteilungen in dispersen Systemen – Teil 2: Disperse Phase
Authors: Ham J.‐H. , Platzer B.
Published: February 2004

No abstracts.
Phasenverhalten (S‐L‐G) und Transporteigenschaften binärer Systeme aus hochviskosen Polyethylenglykolen und komprimiertem Kohlendioxid
Authors: Kukova E. , Petermann M. , Weidner E.
Published: February 2004

No abstracts.
Wirbelstromsensoren als Blasendetektor in der Zweiphasenströmung Gas/Flüssigmetall
Authors: Kaiser E.
Published: February 2004

No abstracts.
Entwicklung eines numerischen Berechnungsverfahrens für Rührwerksschwingungen
Authors: Berger T. , Strohmeier K.
Published: February 2004

No abstracts.
Propanoxidation an Katalysatoren mit Perowskitstruktur im Multimode‐Mikrowellenreaktor – Temperaturmessung und Auswertung der Temperatur‐Umsatzkurven
Authors: Will H. , Scholz P. , Ondruschka B.
Published: February 2004

No abstracts.
Biodiesel – Hoch siedendes Absorbens für die Gasreinigung
Authors: Bay K. , Wanko H. , Ulrich J.
Published: February 2004

No abstracts.
Energiebedarf von Belüftungseinrichtungen in Membranbelebungsanlagen
Authors: Krause S. , Cornel P.
Published: February 2004

No abstracts.
Einfluss einer Laval‐Düse auf die Partikelbildung im Flammenprozess
Authors: Mayer M. , Büttner H. , Ebert F. , Zimmermann G. , Gottfried H. , Michael G.
Published: February 2004

No abstracts.
Die Berechnung von Explosionsgrenzen mit detaillierter Reaktionskinetik
Authors: Markus D. , Maas U.
Published: February 2004

No abstracts.
Behandlung von AOX‐haltigen Abwasserteilströmen aus pharmazeutischen Produktionsprozessen mit Nanofiltration und Umkehrosmose
Authors: Baumgarten G. , Jakobs D. , Müller H.
Published: February 2004

No abstracts.
Untersuchungsmethoden für Biofilmsysteme
Authors: Horn H. , Staudt C. , Neu T. , Leon‐Ohl A. , Bößmann M. , Hempel D. C.
Published: February 2004

No abstracts.
Konzentrationsverteilungen in trocknenden Tropfen
Authors: Brenn G.
Published: February 2004

No abstracts.
Einsatz der Deammonifikation im Moving‐Bed‐Verfahren zur Behandlung hoch stickstoffhaltiger Abwässer
Authors: Rosenwinkel K.‐H. , Cornelius A.
Published: February 2004

No abstracts.
Modellierung und Simulation der H2‐PEM‐Brennstoffzelle
Authors: Meier F. , Eigenberger G.
Published: February 2004

No abstracts.
Mischvorgänge: Klassische Methoden und Computational Fluid Dynamics in der industriellen Praxis
Authors: Himmler K. , Schierholz W. F.
Published: February 2004

Misch‐ und Rührvorgänge zählen zu den wichtigsten Grundoperationen der Verfahrenstechnik. Aus diesem Grund ist die Auslegung und Optimierung dieser Teilprozesse von großer Bedeutung für die Entwicklung und das Design neuer Verfahren. Bei Siemens Axiva werden Misch‐ und Rührvorgänge im Rahmen des „Integrated Process Development”︁ (IPD) sowohl mit klassischen Methoden als auch mit Computational Fluid Dynamics (CFD) untersucht. In diesem Beitrag werden Stärken und Schwächen beider Methoden an einigen Beispielen aufgezeigt und diskutiert. Je nach Frage‐ und Aufgabenstellung kann es sinnvoll sein, ein Problem mit experimentellen Methoden, mit CFD oder mit beiden Methoden gemeinsam zu untersuchen.
Produktdesign – Beschleunigte Entwicklung von Produkten durch Einbeziehung des Kunden
Authors: Rähse W.
Published: February 2004

Im Zuge der Globalisierung erfolgte in den 90er Jahren eine Besinnung der chemischen Industrie auf ihre Kernkompetenz: die Einführung innovativer Produkte. Zur effektiven Entwicklung wurden in einigen Unternehmen die Organisations‐ und Projektstrukturen geändert. Heute steuert ein Team aus Produkt‐ und Verfahrensentwicklern gemeinsam mit dem Marketing die Einzelschritte der Produktentwicklung unter Einbeziehung interner und externer Fachleute. Die Kunden werden von der Produktidee bis zum Markteintritt an der Entwicklung beteiligt, zum einen zur zielgerichteten, beschleunigten Abwicklung und zum anderen zur Minimierung des Floprisikos. Die Konkretisierung neuer Produktideen erfolgt durch Aufzeigen der chemischen und der technischen Möglichkeiten zur Umsetzung, bevor eine Bewertung des Vorschlages erfolgt. Anhand des Innovations‐„Thermometers”︁ kann die Innovationshöhe eingeordnet werden, mit Hilfe des „Barometers”︁ lassen sich die Marktchancen von Ideen abschätzen. Die Produktentwicklung muss bei Marktneuheiten zur Sicherung eines Markterfolgs sehr schnell erfolgen. Eine beschleunigte Produktentwicklung erfordert die Erfüllung von zehn Voraussetzungen, die im Detail erklärt werden. Am Beispiel fester „Waschmittel”︁ wird die Ermittlung von Kundenbedürfnissen diskutiert. Zur Beeinflussung des Partikeldesigns, insbesondere zur Verbesserung der Ästhetik, existiert eine Reihe interessanter, in den Herstellprozess integrierbarer Technologien.
Efferent connections of the nucleus of the lateral olfactory tract in the rat
Authors: Santiago Adriana C. , Shammah‐Lagnado Sara J.
Published: February 2004

The efferent connections of the nucleus of the lateral olfactory tract (LOT) were examined in the rat with the Phaseolus vulgaris leucoagglutinin (PHA‐L) technique. Our observations reveal that layers II and III of LOT have largely segregated outputs. Layer II projects chiefly ipsilaterally to the olfactory bulb and anterior olfactory nucleus, bilaterally to the anterior piriform cortex, dwarf cell cap regions of the olfactory tubercle and lateral shell of the accumbens, and contralaterally to the lateral part of the interstitial nucleus of the posterior limb of the anterior commissure. Layer III sends strong bilateral projections to the rostral basolateral amygdaloid complex, which are topographically organized, and provides bilateral inputs to the core of the accumbens, caudate‐putamen, and agranular insular cortex (dorsal and posterior divisions). Layer II projects also to itself and to layers I and II of the contralateral LOT, whereas layer III projects to itself, to ipsilateral layer II, and to contralateral layer III of LOT. In double retrograde labeling experiments using Fluorogold and cholera toxin subunit b tracers, LOT neurons from layers II and III were found to provide collateral projections to homonymous structures on both sides of the brain. Unlike other parts of the olfactory amygdala, LOT neither projects directly to the extended amygdala nor to the hypothalamus. Thus, LOT seemingly influences nonpheromonal olfactory‐guided behaviors, especially feeding, by acting on the olfactory bulb and on ventral striatal and basolateral amygdaloid districts that are tightly linked to lateral prefrontal cortical operations. J. Comp. Neurol. 471:314–332, 2004. © 2004 Wiley‐Liss, Inc.
Suprachiasmatic nucleus input to autonomic circuits identified by retrograde transsynaptic transport of pseudorabies virus from the eye
Authors: Smeraski Cynthia A. , Sollars Patricia J. , Ogilvie Malcolm D. , Enquist Lynn W. , Pickard Gary E.
Published: February 2004

Intraocular injection of the Bartha strain of pseudorabies virus (PRV Bartha) results in transsynaptic infection of the hypothalamic suprachiasmatic nucleus (SCN), a retinorecipient circadian oscillator. PRV Bartha infection of a limited number of retinorecipient structures, including the SCN, was initially interpreted as the differential infection of a subpopulation of rat retinal ganglion cells, followed by replication and anterograde transport via the optic nerve. A recent report that used a recombinant strain of PRV Bartha (PRV152) expressing enhanced green fluorescent protein demonstrated that SCN infection actually results from retrograde transneuronal transport of the virus via the autonomic innervation of the eye in the golden hamster. In the present study using the rat, the pattern of infection after intravitreal inoculation with PRV152 was examined to determine if infection of the rat SCN is also restricted to retrograde transsynaptic transport. It was observed that infection in preganglionic autonomic nuclei (i.e., Edinger‐Westphal nucleus, superior salivatory nucleus, and intermediolateral nucleus) precedes infection in the SCN. Sympathetic superior cervical ganglionectomy did not abolish label in the SCN after intraocular infection, nor did lesions of parasympathetic preganglionic neurons in the Edinger‐Westphal nucleus. However, combined Edinger‐Westphal nucleus ablation and superior cervical ganglionectomy eliminated infection of the SCN. This observation allowed a detailed examination of the SCN contribution to descending autonomic circuits afferent to the eye. The results indicate that in the rat, as in the hamster, SCN infection after intraocular PRV152 inoculation is by retrograde transsynaptic transport via autonomic pathways to the eye. J. Comp. Neurol. 471:298–313, 2004. © 2004 Wiley‐Liss, Inc.
Distribution of anterogradely labeled trigeminal and auditory nerve boutons on abducens motor neurons in turtles: Implications for in vitro classical conditioning
Authors: Keifer Joyce , Mokin Maxim
Published: February 2004

A conditioned abducens nerve response is generated in in vitro brainstem preparations from turtles by pairing a weak conditioned stimulus (CS) applied to the auditory nerve that immediately precedes an unconditioned stimulus (US) applied to the trigeminal nerve. Tract‐tracing studies showed direct projections from auditory and trigeminal nerves to abducens motor neurons. In light of these findings for convergent CS‐US inputs, it is hypothesized that auditory and trigeminal nerve synaptic inputs onto abducens motor neurons are in spatial proximity because the CS is a weak input that may be required to be near the US inputs to have an associative effect, and conditioning occurs only when the CS and US are temporally separated by less than 100 ms. This study examined the spatial relationship of 133 anterogradely labeled synaptic boutons conveying CS or US information on retrogradely labeled abducens motor neurons. The results show that trigeminal and auditory nerve terminal fields occupy primarily the soma and proximal dendrites of abducens motor neurons. Quantitative analysis shows that the majority of labeled boutons (76% and 85% from injections of the trigeminal and auditory nerves, respectively) were apposed to somata or were localized to dendritic segments no more than about 30 μm from the nucleus. There were no quantitative differences between trigeminal and auditory nerve boutons in terms of their localization on dendrites or bouton diameter. Finally, triple labeling experiments demonstrated that individual abducens motor neurons receive inputs from both nerves and that these inputs may be in close spatial proximity to one another. This synaptic arrangement allows for the possibility that in vitro abducens conditioning is generated by coincident CS‐US detection mediated by NMDA receptors and may utilize a Hebbian‐like plasticity mechanism. J. Comp. Neurol. 471:144–152, 2004. © 2004 Wiley‐Liss, Inc.
NT3 expressed in skin causes enhancement of SA1 sensory neurons that leads to postnatal enhancement of Merkel cells
Authors: Krimm Robin F. , Davis Brian M. , Woodbury C. Jeffery , Albers Kathryn M.
Published: February 2004

To determine the role of NT3 in the postnatal maturation of Merkel cell (MC) sensory neurite complexes (touch domes), we examined the development of their neural and end‐organ components in wild‐type and transgenic mice that overexpress NT3 (NT3‐OE). Touch domes are sensory complexes of the skin that contain specialized MCs innervated by slowly adapting type 1 (SA1) neurons. Touch domes are dependent on NT3 and, though formed in newborn mice that lack NT3, are severely depleted during postnatal maturation. Mice that overexpress NT3 in the skin have larger touch domes characterized by enhanced neural innervation and MC number. In this study, we asked how this NT3‐mediated enhancement occurs, whether through stimulatory effects of NT3 on the SA1 neuron, or the MC, or both. The innervation density and number of MCs associated with each touch dome were measured in wild‐type and transgenic animals at postnatal times. In newborn NT3‐OE mice, touch dome innervation was enhanced. Surprisingly, however, the number of MCs was lower in newborn NT3‐OE animals than in wild‐type littermates, and equivalent numbers were not reached until postnatal day 8 (PN8). Not until the PN12 and PN16 time points did MCs increase in NT3‐OE mice. To examine the neural dependence of MCs in NT3‐OE mice, touch domes were chronically denervated by resecting dorsal cutaneous nerves. Both wild‐type and NT3‐OE animals showed similar depletion in the number of MCs associated with touch domes. These data indicate that NT3 is not a survival factor for MCs and that the NT3‐mediated enhancement of MC number is indirect and neurally dependent. J. Comp. Neurol. 471:352–360, 2004. © 2004 Wiley‐Liss, Inc.