bluuebunny/crossref_metadata_2025 huggingface dataset:
Extended presentation of specific MHC‐peptide complexes by mature dendritic cells compared to other types of antigen‐presenting cells
Authors: Zehn Dietmar , Cohen Cyril J. , Reiter Yoram , Walden Peter
Published: May 2004

Dendritic cells are known as the most potent antigen‐presenting cells for the induction of T cell‐mediated immune responses. To discriminate between the presentation of antigens and the co‐stimulatory aspects of this high immunostimulatory capacity, we used recombinant antibodies with T cell receptor‐like specificity to detect defined MHC‐peptide complexes on living cells. Mature human dendritic cells (mDC) were compared with immature DC (iDC), monocytes, CD4+ T lymphocytes, melanoma cells, T2 cells and B lymphoblastoid cells for their capacity to present MHC class I‐restricted tumor‐associated T cell epitopes and were found to display the specific peptides two to six times longer than other cells. The most short‐lived peptide had an average half‐life of 8.7 h on mDCvs. 3.5 h on B lymphoblastoid cells, while the most long‐lived peptide had a half‐life of 118.5 h vs. 20.7 h on these two cell types. The decay kinetics of specific MHC‐peptide complexes on iDC were among the fastest observed. The high potency of dendritic cells to induce specific T cell responses is thus based, in addition to the expression of co‐stimulatory molecules, on an extended antigenic memory, which increases the likelihood and the extent of contacts between dendritic cells and antigen‐specific T cells.
AgC10, a mucin from Trypanosoma cruzi, destabilizes TNF and cyclooxygenase‐2 mRNA by inhibiting mitogen‐activated protein kinase p38
Authors: Alcaide Pilar , Fresno Manuel
Published: May 2004

Secretion of proinflammatory mediators by activated macrophages plays an important role in the immune response to Trypanosoma cruzi. We have previously reported that AgC10, a glycosylphosphatidylinositol‐anchored mucin from T. cruzi, inhibits TNF secretion by activated macrophages (de Diego, J., Punzon, C., Duarte, M. and Fresno, M., Alteration of macrophage function bya Trypanosoma cruzi membrane mucin. J. Immunol. 1997. 159: 4983–4989). In this report we have further investigated the molecular mechanisms underlying this inhibition. AgC10 inhibited TNF, IL‐10 and cyclooxygenase‐2 (COX‐2) synthesis by macrophages activated with LPS or LPS plus IFN‐γ in a dose‐dependent manner. AgC10 did not affect other aspects of macrophage activation induced by LPS, such as inducible nitric oxide synthase (iNOS) expression. AgC10 also had no effect on TNF or COX‐2 transcription or the induction of their promoters but inhibited the stability of TNF and COX‐2 mRNA, which are regulated post‐transcriptionally by the mitogen‐activated protein kinase (MAPK) p38 pathway. AgC10 was found to inhibit both the activation and the activity of p38 MAPK, since MAPK activated protein kinase‐2 (MAPKAP‐K2 or MK‐2) phosphorylation was also strongly inhibited. This led to TNF and COX‐2 mRNA destabilization. In contrast, AgC10 did not affect p38 activation induced by TNF. Furthermore, AgC10 inhibition must lie upstream in the MAPK activation pathway by LPS, since this mucin also inhibited extracellularly regulated kinase (ERK) and Jun kinase (JNK)activation.
Interferon γ suppresses glucocorticoid augmentation of macrophage clearance of apoptotic cells
Authors: Heasman Sarah J. , Giles Katherine M. , Rossi Adriano G. , Allen Judith E. , Haslett Christopher , Dransfield Ian
Published: May 2004

One of beneficial effects of glucocorticoids (GC) in inflammation may be the augmentation of macrophages' capacity for phagocytosis of apoptotic cells, a process that has a central role in resolution of inflammation. Here we define the phenotype of GC‐treated monocyte‐derived macrophages, comparing to IFN‐γ‐treated and IL‐4‐treated monocyte‐derived macrophages and combinatorial treatment. Our data indicate that the cytokine microenvironment at an inflammatory site will critically determine monocyte functional capacity following treatment with GC. In particular, whilst GC exert dominant regulatory effects over IFN‐γ in terms of cell surface receptor repertoire and morphology, the acquisition of a macrophage capacity for clearance of apoptotic cells is prevented bycombined treatment. In terms of mechanism, GC augmentation of phagocytosis was reversed even when monocytes were pre‐incubated with GC for the first 24 h of culture, a period that is critical for induction of a highly phagocytic macrophage phenotype. These findings have important implications for the effectiveness of GC in promoting acquisition of a pro‐phagocytic macrophage phenotype in inflammatory diseases associated with high levels of IFN‐γ
Homophilic interaction of NTBA, a member of the CD2 molecular family: induction of cytotoxicity and cytokine release in human NK cells
Authors: Falco Michela , Marcenaro Emanuela , Romeo Elisa , Bellora Francesca , Marras Daniele , Vély Frédéric , Ferracci Géraldine , Moretta Lorenzo , Moretta Alessandro , Bottino Cristina
Published: May 2004

NK‐T‐B antigen (NTBA) is a CD2 family member that functions as a coreceptor in human NK cell activation. Several receptor/ligand interactions occur between different members of this molecular family. In this study, in order to identify the natural ligand of NTBA, we produced a chimeric protein formed by the NTBA extracellular region fused with the Fc portion of human IgG1 (termed NTBA‐Fc*). NTBA‐Fc* specifically binds to NTBA cell transfectants but not to cells transfected with other CD2 family members including CD2, CD48, CD84, CD150, CD229, and CD244. Moreover, NTBA‐Fc* also binds to NTBA+ but not to NTBA– T cell lines. Enzyme‐linked immunosorbent assays, plasmon resonance analysis, as well as NTBA‐Fc*‐mediated down‐regulation of NTBA surface expression further confirmed the occurrence of NTBA/NTBA homophilic interaction. Functionally, in NK cells, NTBA‐Fc* promoted a strong production of IFN‐γ and TNF‐α. Moreover, NTBA‐transfected targets displayed increased susceptibility to NK‐mediated killing as compared to untransfected cells and this effect was specifically inhibited by anti‐NTBA mAb. Altogether our data indicate that NTBA is characterized by self recognition.
The frictional resistance characteristics of a bedrock‐influenced river channel
Authors: Heritage G. L. , Moon B. P. , Broadhurst L. J. , James C. S.
Published: May 2004

Much of the published literature relating to reach‐scale total ﬂow resistance concentrates on alluvial rivers and little mention is made of the more extreme resistance found in bedrock‐inﬂuenced river systems. This paper presents the results of a detailed investigation of total ﬂow resistance variation for ﬁve channel types on the Sabie River, South Africa (cohesive mixed anastomosed, uncohesive mixed anastomosed, mixed pool–rapid, alluvial braided and alluvial single thread) over a range of discharges. Manning's ‘n’ and Darcy‐Weisbach f resistance coefﬁcients are calculated using Barnes' methodology (H. H. Barnes, US Geological Survey Water Supply Paper 1849, 1967). These data are analysed at the scales of channel type and morphologic unit and the resultant resistance values are compared with the literature. Generally the low‐ﬂow friction values estimated for the bedrock‐inﬂuenced channel types are higher than any reported. Flow resistance quantiﬁcation of the alluvial channel type study sites on the Sabie River produced values slightly higher than earlier studies of similar morphologies. In situations where signiﬁcant areas of irregular bedrock are exposed (cohesive mixed anastomosed and mixed pool–rapid channel types) the high ﬂow resistance coefﬁcients at low discharges probably reﬂect energy dissipation due to hydraulic jumps and internal distortions; however, these values fall as discharge increases to values comparable to those recorded for step–pool rivers. It is suggested that the slightly elevated resistance coefﬁcients recorded in the alluvial channel types are the result of the vegetation roughness component, operating when the macro‐channel bar features are inundated. Copyright © 2004 John Wiley & Sons, Ltd.
Centrosome amplification and aneuploidy in bone marrow failure patients
Authors: Kearns William G. , Yamaguchi Hiroki , Young Neal S. , Liu Johnson M.
Published: May 2004

Patients with bone marrow failure are at risk for development of hematopoietic progenitor clones with abnormal numbers of chromosomes (aneuploidy) and leukemia. Numerical centrosome abnormalities or mutations in genes associated with the mitotic spindle checkpoint (BUB1 and MAD2) are two important mechanisms that can induce abnormal mitosis resulting in aneuploid daughter cells. To assess the role of these mechanisms, we used fluorescence in situ hybridization techniques to determine aneuploidy and centrosome copy number and PCR‐SSCP to identify gene mutations of BUB1 and MAD2 in marrow cells of 25 patients. No mutations were found in BUB1 or MAD2 genes. However, we found that cells with more than two centrosomes exhibited aneuploidy for three or more chromosomes. We conclude that centrosome amplification may be associated with the development of a clonal population of potentially preleukemic aneuploid cells. © 2004 Wiley‐Liss, Inc.
Rural tourism in Spain
Authors: Barke Michael
Published: May 2004

The paper describes the rapid recent growth in rural tourism facilities in Spain and attempts to account for the regional variations that exist. The range of activities involved in rural tourism is described and a significant trend towards the development of ‘active’ leisure pursuits in rural areas is identified. This clearly implies a major change in the use of the countryside, albeit in specific locations, but therefore calls into question the assertion of some scholars that rural restructuring is not a feature of contemporary Spain. In assessing the wider impact of rural tourism policies as part of overall rural development, however, it is clear that the main beneficiaries are not necessarily local residents. Copyright © 2004 John Wiley & Sons, Ltd.
Rural tourism development in the USA
Authors: Gartner William C.
Published: May 2004

Rural tourism has been a subject of study since the early days of tourism scholarship. Most of tourism's deleterious impacts were identified from studies conducted in rural settings. It is only recently, however, that rural tourism has become a special focus of study, dissimilar enough from urban tourism, to be a study subject unto itself.

This paper reviews some of the history of rural tourism development in North America with most of the attention paid to the USA's experience, with some examples from Canada. The reason for this is the huge economic difference between the two countries with respect to tourism flows and impacts. In reviewing the history of rural development in the USA, the argument is made that most developments are unplanned and result from market and economic forces that have greatly transformed the American rural landscape. A review of these transformational forces is provided. It is also shown that rural destinations are used, primarily, by local tourists and do not, with few exceptions, cater to an international clientele.

After the historical perspective is presented an argument is made that current rural tourism development practices rely on an old paradigm, which is to use local attributes as the primary basis for development and marketing strategies. This has led, in recent years, to a great deal of development attention being paid to the cultural/heritage attributes of a place. Using research conducted in the state of Minnesota on highway travellers and tourists to rural destinations, a new way to look at actual and potential visitors is offered. Instead of an attribute‐specific development approach, a benefits‐based model is suggested as a different way to position rural tourism destinations. Copyright © 2004 John Wiley & Sons, Ltd.
Sustainable leisure life modes and rural welfare economy. The case of the Randers Fjord area, Denmark
Authors: Hjalager Anne‐Mette
Published: May 2004

As increasing attention has been paid to rural tourism as a specific form of tourism development, so too has the scope of research into tourism in rural areas become more diverse. Typically, studies focus primarily upon the economic developmental contribution of rural tourism, although a significant amount of work has been undertaken on the consequences of rural tourism development and attitudes/motivations on the part of visitors and/or local communities. However, no attempt has yet been made to integrate studies of both visitors and local communities within the framework of rural tourism development policy.

The purpose of this paper is to address this gap in the literature. Drawing on a study of tourism in the Randers Fjord, a relatively underdeveloped area of rural Denmark, it identifies and analyses three groups of tourists characterised by life modes: (i) traditionalists, (ii) peace seekers and (iii) adventurers. In each case, expectations, behaviour and future needs are revealed through qualitative interviews. The predominant (traditionalist) life mode of tourists, it is argued, closely matches that of the area's residents. This, the paper suggests, presents significant barriers to the development and enhancement of tourism, as do the prevailing economic structures and employment patterns. Thus, tourism development policy should take into account both tourists' and locals' life modes in order to progress towards sustainable rural tourism development. Copyright © 2004 John Wiley & Sons, Ltd.
Rural tourism — meeting the challenges of the new South Africa
Authors: Briedenhann Jennifer , Wickens Eugenia
Published: May 2004

Rural tourism in South Africa has undergone fundamental change since the advent of political democracy in 1995. Previously perceived as a ‘white man's thing’, rural tourism is increasingly finding a home amongst South Africa's formerly marginalised rural communities. The country has considerable potential in attracting tourists in search of new, exciting experiences in areas of unexploited natural beauty and rich cultural resources. The concept of rural tourism has mushroomed to include adventure tourism activities, cultural tourism and, lately, a new phenomenon in rural communities known as ‘township tourism’. There are, however, substantial challenges to be overcome if the rural tourism sector is to achieve its goals. These include a lack of capacity at local government level, the difficulties involved in operationalising community‐based rural tourism and the dearth of entrepreneurial expertise, management skills and capital with which to expand the rural tourism infrastructure. Copyright © 2004 John Wiley & Sons, Ltd.
Thermotropic Liquid Crystals of Main‐Chain Polyesters having a Mesogenic 4,4′‐Biphenyldicarboxylate Unit, 14
Authors: Osada Kensuke , Koike Masao , Tagawa Hirotaka , Tokita Masatoshi , Watanabe Junji
Published: May 2004

Summary: Anisotropy in molecular motions of a glassy smectic CA (SmCA) liquid crystal of a main‐chain BB‐5(3‐Me) polyester was examined by dynamic mechanical analysis (DMA) for fibrous monodomain samples with two distinct orientations of smectic layers perpendicular and parallel to the fiber axis. The α‐process attributed to micro‐Brownian motion of the polymer on the glass transition shows clear anisotropy explainable by the nature of the smectic layer structure. Time‐temperature superposition is applicable to the α‐process, so that the frequency of the micro‐Brownian motion in the SmCA phase can be estimated despite the narrow frequency range in DMA. The results suggest that the decoupling of the molecular motions in two characteristic directions are parallel and perpendicular to the layer. The amplitude of the micro‐Brownian motion in the layer normal direction is 3 times smaller than that in the layer direction, and the frequency in the layer normal direction is 2.5 times higher than that in the layer direction.

Illustration of molecular packing structures: fiber A (left side) and fiber B (right side) with the orientations of polymers parallel and perpendicular to the fiber, respectively.

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Illustration of molecular packing structures: fiber A (left side) and fiber B (right side) with the orientations of polymers parallel and perpendicular to the fiber, respectively.
A Model Study of Ti(OBu)4 Catalyzed Reactions during Reactive Blending of Polyethylene (PE) and Poly(ethylene terephthalate) (PET)
Authors: Coltelli Maria‐Beatrice , Savi Stefania , Della Maggiore Irene , Liuzzo Vincenzo , Aglietto Mauro , Ciardelli Francesco
Published: May 2004

Summary: The effect of metal catalysts in promoting the formation of the comb copolymer between a very low density polyethylene (VLDPE) grafted with diethyl maleate and PET has been studied in this paper following a model study based on low molecular weight molecules resembling the local structure of the reactive groups in the reference macromolecules. Ti(OBu)4 was used as the catalyst and the reactions were carried out under the same conditions as in the case of the macromolecules species. The model mixtures have been analyzed by FT‐IR, 1H and 13C NMR spectroscopy, thermogravimetric analysis (TGA) and GC‐MS and evidence of the degradation of ester bonds, deactivation of hydroxyl terminals of PET and the possible crosslinking of functionalized polyolefin have been observed. The molecular model process agrees with results obtained for the macromolecular system blending PET and VLDPE grafted with diethyl maleate in a Brabender mixer in the presence of Ti(OBu)4, as evaluated by mixer torque values and selective extraction results. Therefore, the present model study allows us to both obtain information about reaction mechanism in the complex melt biphasic system and to suggest new strategies to optimize the process.

Brabender torque/time graphics of PET in presence of different amounts of Ti(OBu)4.

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Brabender torque/time graphics of PET in presence of different amounts of Ti(OBu)4.
Deactivation Kinetics of Metallocene‐Catalyzed Ethene Polymerization at High Temperature and Elevated Pressure
Authors: Dornik Hans Peter , Luft Gerhard , Rau Alexander , Wieczorek Thomas
Published: May 2004

Summary: The kinetics of ethene polymerization with metallocene/[Me2PhNH]+[B(C6F5)4]−/AliBu3 (ternary systems) and metallocene/methylaluminoxan (MAO) systems respectively has been investigated at 100–140 °C and 7 MPa. Overall, eight different unbridged and ansa‐metallocenes were tested. The effect of ligand structure, cocatalyst and catalyst concentration on the thermostability and the activation energy of deactivation were studied. Deactivation with respect to the catalyst concentration followed a first order reaction. The half‐life as well as the activation energy of the ternary systems depended strongly on ligand structure while the ligand structure of MAO‐activated metallocenes merely influenced the half‐life. The half‐life associated with MAO activation is approximately twice as high as that in ternary activation. Based on these results, conclusions about the deactivation reactions have been drawn.

Influence of catalyst concentration on deactivation.

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Influence of catalyst concentration on deactivation.
Co‐Micellization Investigated by Pulsed Field Gradient‐NMR Spectroscopy
Authors: Gröger Stefan , Geschke Dieter , Kärger Jörg , Stallmach Frank , Koňák Čestmír
Published: May 2004

Summary: Pulse field gradient‐NMR (PFG‐NMR) spectroscopy is determined to be a more suitable method for the investigation of self‐association processes in multi‐component (co)polymer systems than light scattering methods. Here the co‐micellization of mixtures of the diblock copolymer polystyrene‐block‐(hydrogenated polyisoprene) (PS‐HPI) and the triblock copolymer polystyrene‐block‐(hydrogenated polybutadiene)‐block‐polystyrene (PS‐HPB‐PS) in decane is investigated by PFG‐NMR spectroscopy and the results compared to those experimentally determined by static (SLS) and dynamic (DLS) light scattering. As expected, diffusion coefficients determined by PFG‐NMR spectroscopy are systematically lower than those from DLS. The PFG‐NMR measurements provided higher values of c(X)/ctot than the model calculations, illustrating that the basic assumption used in the calculations, i.e., that the number concentration of co‐micelles in mixed solutions follows the dilution with a triblock copolymer solution, 1 − X, is not fully valid at high X (weight fraction of PS‐HPB) values.

Comparison of PFG‐NMR spectroscopy and SLS (c/ctot = equilibrium concentration of free PS‐HPB‐PS over the total concentration of copolymers in solution, X = weight fraction of PS‐HPB).

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Comparison of PFG‐NMR spectroscopy and SLS (c/ctot = equilibrium concentration of free PS‐HPB‐PS over the total concentration of copolymers in solution, X = weight fraction of PS‐HPB).
Structure Formation During the Isothermal Crystallization of an Oriented Blend of Isotactic Polystyrene with Poly(2,6‐dimethyl‐1,4‐phenylene oxide)
Authors: Dikshit Asok Kumar , Kaito Akira
Published: May 2004

Summary: Isothermal crystallization of an oriented blend of isotactic polystyrene (iPS) with poly(2,6‐dimethyl‐1,4‐phenylene oxide) (PPO) was studied by in situ polarized FT‐IR spectroscopy and wide‐angle X‐ray diffraction. The structural organization during the oriented crystallization consists of three stages. The first stage is the orientation relaxation of molecular chains of iPS and PPO, the degree of orientation of iPS increases in the second stage, and the oriented chains of iPS crystallize in the third stage.

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Mimetics of Eggshell Membrane Protein Fibers by Electrospinning
Authors: Yi Feng , Guo Zhao‐Xia , Hu Ping , Fang Zhuang‐Xi , Yu Jian , Li Qiang
Published: May 2004

Summary: Mimetics of eggshell membrane protein fibers have been obtained with an electrospinning technique based on soluble eggshell membrane protein (SEP) prepared previously. Poly(ethylene oxide), a biocompatible and water soluble polymer, is used to improve the processability of SEP. Blends of SEP/PEO aqueous solutions were electrospun. The diameters of the fibers are 0.3–20 μm depending on the concentration of the solution and the proportion of SEP/PEO. Two “cross‐linking” methods are investigated in order to improve the anti‐water property of the fibers.

Scanning electron micrograph of electrospun fibers.

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Scanning electron micrograph of electrospun fibers.
Redox Materials by the Covalent Entrapment of Redox‐Active Dirhodium(II,II) Species in a Siloxane Network
Authors: Lo Schiavo Sandra , Forte Claudia , Pignataro Bruno , Tresoldi Giuseppe , Piraino Pasquale
Published: May 2004

Summary: Hydrolysis and polycondensation of the coupling agent (aminopropyl)triethoxysilane (APS), axially coordinated to the redox‐active complex [Rh2(form)2(CH3COO)2(APS)2], lead to the insertion of redox‐active inorganic microdomains into a siloxane network; the new polymers undergo cyclic redox reactions indicating that dirhodium(II,II) centres retain their redox activity even when incorporated into siloxane networks.

The redox‐active complex [Rh2(form)2(CH3COO)2(APS)2] (form = N,N′‐di‐p‐tolylformamidinate) incorporated into a siloxane network here.

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The redox‐active complex [Rh2(form)2(CH3COO)2(APS)2] (form = N,N′‐di‐p‐tolylformamidinate) incorporated into a siloxane network here.
Synthesis and Properties of a Novel Thiophene‐Based Conducting Copolymer with Mesogenic Groups Attached Parallel to the Polymer Backbone
Authors: Brown John W. , Lambe Gillian J. , Foot Peter J. S. , Clipson Jacqueline A.
Published: May 2004

Summary: A novel thiophene‐based conducting copolymer has been synthesised with mesogenic groups attached parallel to the conducting polymer backbone; preliminary data are reported on its properties. These indicate that as the nonmesogenic intermediate polymer is converted into a liquid‐crystalline polymer there is a significant increase in conductivity. Measurement of the temperature‐dependent conductivity indicates a reduction of the activation energy in the liquid‐crystalline phase.

Poly[(1‐(thiophene‐3‐methyloxy)‐6‐(4‐n‐hexyloxy‐2‐oxybenzoic acid)hexane)‐co‐(3‐n‐hexylthiophene)].

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Poly[(1‐(thiophene‐3‐methyloxy)‐6‐(4‐n‐hexyloxy‐2‐oxybenzoic acid)hexane)‐co‐(3‐n‐hexylthiophene)].
Copolymerization of Propene and Buta‐1,3‐diene in the Presence of Highly HinderedC2‐Symmetric Zirconocene‐Based Catalyst
Authors: Pragliola Stefania , Costabile Chiara , Di Bartolomeo Francesca , Longo Pasquale
Published: May 2004

Summary:Copolymerizations of propene and buta‐1,3‐diene performed in the presence ofrac‐[CH2(3‐tert‐butyl‐1‐indenyl)2]ZrCl2and methylaluminoxane (MAO) have been investigated. Buta‐1,3‐diene gives prevailingly primary coordination to the metal, producing overall 1,2 units. Cyclopropane and cyclopentane rings, although in low amounts, are also obtained. The presence of butadiene would be responsible for some regioirregular 2,1‐inserted propene units, which at high temperatures give rearrangement to 3,1 units.

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MAO‐Free Activation of Metallocenes and other Single‐Site Catalysts for Ethylene Polymerization using Spherical Supports based on MgCl2
Authors: Severn John R. , Chadwick John C.
Published: May 2004

Summary: Supports of type MgCl2/AlRn(OEt)3−n, obtained by reaction of AlR3 with adducts of MgCl2 and ethanol, have been shown to be effective for the immobilization and activation of [Cp2TiCl2] and other single‐site olefin polymerization catalysts without the use of methylaluminoxane or a borate activator. Polyethylene with a spherical particle morphology and narrow molecular weight distribution was obtained.

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Synthesis and properties in solution of rodlike polyelectrolytes
Authors: Ballauff Matthias , Blaul Jürgen , Guilleaume Birgit , Rehahn Matthias , Traser Steffen , Wittemann Matthias , Wittmeyer Patrick
Published: May 2004

Efficient synthetic strategies are described for the preparation of rodlike polyelectrolytes based on the intrinsically rigid poly(p‐phenylene). Uncharged precursors were first prepared via the Suzuki coupling and then characterized by different methods of polymer analysis. Finally, they were transformed into polyelectrolytes using macromolecular substitution reactions. Depending on the substitution pattern, the obtained polyelectrolytes are either soluble or insoluble in water. Using water‐soluble derivatives, the Poisson‐Boltzmann cell model was tested by osmotic measurements and small‐angle X‐ray scattering. It is shown that the cell model provides a good first approximation of the distribution of the counterions around the macroion but still underestimates their correlation. Moreover, the PPP polyelectrolytes show a very pronounced polyelectrolyte effect. Since the rodlike PPPs are very rigid in shape, this observation proves that the polyelectrolyte effect is caused by long‐range intermolecular electrostatic repulsion of the dissolved macroions rather than due to conformational changes.
Particle scattering factor of pearl necklace chains
Authors: Schweins Ralf , Huber Klaus
Published: May 2004

The particle scattering behaviour of a pearl necklace chain is derived. The chain is composed of sphere‐like pearls, separated by rod‐like segments of fixed length, which have no angular restrictions. By calculating several series of model scattering curves, the important structural features are retrieved. The model is believed to be useful in interpreting intermediate structures of collapsing macromolecules or polyelectrolytes. A first application to a shrinking polyelectrolyte coil generated by molecular dynamic simulations (Limbach and Holm, J.Phys.Chem. 2003) is presented and used to discuss the potentials and limits of the model.
Conformations and solution structure of polyelectrolytes in poor solvent
Authors: Limbach Hans Jörg , Holm Christian , Kremer Kurt
Published: May 2004

Using extensive Molecular Dynamics (MD) simulations we study the behavior of polyelectrolytes in poor solvents, where we take explicitely care of the counterions. The resulting pearl‐necklace structures are subject to strong conformational fluctuations, only leading to small signatures in the form factor, which is a severe obstacle for experimental observations. In addition we study how the necklace collapses as a function of Bjerrum length. At last we demonstrate that the position of the first peak in the inter‐chain structure factor varies with the monomer density close to $ρ^{1/3}_{m}$ for all densities. This is in strong contrast to polyelectrolyte solutions in good solvent.
Counterion mobility and effective charge of polyelectrolytes in solution
Authors: Böhme Ute , Scheler Ulrich
Published: May 2004

Polyelectrolytes are macromolecules containing dissociable or charged groups. The charge, that is effectively accessible, is determined by counterion condensation, which is strongly influenced by the ionic strength of the solution under study. In general a rapid exchange between free and condensed counterions is expected. In the present study diffusion and electrophoretic mobility of poly(diallyldimethylammoniumchloride) and perfluorinated succinic acid have been monitored simultaneously. Condensation of the perfluorinated succinic acid to the macroion shows in the electrophoretic mobility of succinic acid monitored by pulsed field gradient NMR. In the concentration dependence of the averaged diffusion coefficient and electrophoretic mobility an exchange fast on the time scale of the NMR experiment is manifested.
Poly(styrene sulfonate) self‐organization: electrostatic and secondary interactions
Authors: Ahrens H. , Büscher K. , Eck D. , Förster S. , Luap C. , Papastavrou G. , Schmitt J. , Steitz R. , Helm C.A.
Published: May 2004

We investigate the self‐organization of PSS in brushes and polyelectrolyte multilayers with X‐ray, neutron and optical reflectivity. The electrostatic force dominates brush phases and adsorption behavior, additionally we find evidence of a strong hydrophobic force: (ι) within amphiphilic diblock copolymer monolayers, a PSS monolayer adsorbs flatly to the hydrophobic block, (ιι) on temperature increase (and with screened electrostatic forces), more PSS is adsorbed onto oppositely charged surfaces, and (ιιι) a polyelectrolyte multilayers shrinks when heated at 100% r.h. The latter two effects are consistent with the well‐known increase of the hydrophobic force on heating: The increased PSS surface coverage can be attributed to deteriorating solvent conditions. Within a polyelectrolyte multilayer, an increase of the hydrophobic force maximizes the local contact of hydrophobic polymer segments, causing a reduction of swelling and an increased mass density.
Charge density, solvent polarity and counterion nature effects on the solution properties of some polycations
Authors: Dragan Stela , Ghimici Luminita , Wandrey Christine
Published: May 2004

The electrolytic conductivity and solution viscosity of some strong polycations, which possess the ammonium quaternary centers either attached to an acrylic macromolecular chain (polycation PDMAEMQ type), or in the backbone (polycation PCA type), have been measured in order to identify how charge density, polyelectrolyte concentration, solvent polarity as well as counterion nature influence the ultimate solution properties. The investigations reveal for all polycations an increase of the equivalent conductivity with decreasing concentration. The onset of the strong increase shifts to lower concentration if the charge density augments. Polyelectrolyte behavior was observed for PCA5D1 in the mixture of water/methanol for all solvent compositions employed and in the mixture of water/acetone up to 60 vol% of acetone content. At all experimental concentrations the reduced viscosity decreases with the dielectric constant of the mixed solvent. Furthermore, the specific interaction between several mono‐ and divalent counterions with some of these polycations was clearly proved by conductometric measurements.
Self‐assembly in ternary systems: cross‐linked polyelectrolyte, linear polyelectrolyte and surfactant
Authors: Zezin Alexander B. , Rogacheva Valentina B. , Novoskoltseva Olga A. , Kabanov Victor A.
Published: May 2004

The competitive interactions in ternary systems consisting of a slightly cross‐linked polyelectrolyte hydrogel and the mixture of linear polyelectrolyte and micelle forming surfactant both oppositely charged relative to the polyelectrolyte network were studied. It was shown that the equilibrium in the competitive reactions depends on the linear polyion charge density and the length of the surfactant aliphatic radical. Dependency on these characteristics the interpolyelectrolyte complex formed by cross‐linked and linear polyelectrolytes can uptake surfactant ions from water solution transforming into the cross‐linked polyelectrolyte‐surfactant complex and releasing the linear polyelectrolyte or vice versa. The ternary systems of this kind are perspective to design the novel family of delivery constructs.
Polyelectrolytes on block copolymer surfaces
Authors: Brehmer Martin , Funk Lutz , Conrad Lars , Allard Dirk , Theato Patrick
Published: May 2004

Soft lithography and properties of amphiphilic block copolymers are combined in a new technique for the generation of patterned substrates, which can be used in different ways as templates for further processing. In these processing steps the deposition of polyelectrolytes, metals and grafting from polymerizations are used for the construction of different structures.
Comparison of polyelectrolyte multilayers built up with polydiallyldimethylammonium chloride and poly(ethyleneimine) from salt‐free solutions by in‐situ surface plasmon resonance measurements
Authors: Schwarz Simona , Nagel Jürgen , Jaeger Werner
Published: May 2004

Polyelectrolytes offer a widespread potential for the defined modification of planar inorganic or polymer surfaces. Essential parameters for the regular adsorption of subsequent polymer layers by electrostatic interactions are the charge of polyelectrolyte and of the outermost surface region, the surface of the substrate, and the molar mass of the polyelectrolyte.

To study such effects in mono‐ and multilayers we used poly(diallyldimethylammonium chloride (PD) with a molar mass from 5000 to 400000 g/mol as a strong polycation and poly(ethyleneimine) (PEI) with 75000 g/mol as a weak polycation and poly(sodium styrenesulfonate) (PSS) from 70000 to 1Mio g/mol in the diluted and semi‐diluted region.

The characterization of the layers was performed by streaming potential, in‐situ SPR and UV‐Vis spectroscopy. Thereby the layer built up at the solid/liquid‐interface could be followed and quantified at the molecular level. SPR revealed that the thicknesses of the multilayer depends strongly on pK values of the polyelectrolyte (strong or weak) and the molar masses. We observed a linear growth if both polyelectrolytes are strong and an exponential growth if one polyelectrolyte is weak. The thickness increased with higher molar masses of the polyelectrolytes. The process was followed in‐situ in short time steps.
Multilayers consisting of oriented charged α‐helical polypeptides
Authors: Müller Martin , Reihs Thomas , Kessler Bernd , Adler Hans‐Jürgen , Lunkwitz Klaus
Published: May 2004

Polyelectrolyte Multilayers (PEMs) consisting of cationic α‐helical poly(L‐lysine) (PLL) and optionally anionic poly(vinysulfate) (PVS) (i) or α‐helical poly(L‐glutamic acid) (PLG) (ii) were deposited at substrates texturized by parallel nanoscopic surface grooves, respectively. Using dichroic Attenuated Total Reflexion Fourier Transform Infrared (ATR‐FTIR) spectroscopy the consecutive deposition, conformation and macromolecular order of stiff polyelectrolytes within PEMs were studied. From the dichroic ratios of the Amide I and Amide II bands order parameters S ⩾ 0.6 (S = 1 for high, S = 0 for low order) were obtained suggesting a significant alignment of charged α‐helical polypeptides in PEMs. For the PEM consisting of PLL/PVS the deposited amount as well as the order parameter S significantly depended on the molecular weight (contour length) of PLL. Furthermore, the related opening angle γ of a model cone consisting of α‐helical PLL rods was proven to be a function of both contour length and width of the confining surface grooves. AFM pictures on PEM‐PLL/PVS showed anisotropically oriented worm‐like structures As a second system PEMs of PLL and PLG, both in the α‐helical conformation, are introduced. A high order parameter of both spectroscopically indistinguishable polypeptides was found. A model of aligned rod/coil (i) and rod/rod (ii) structures was proposed. Finally, multilayers of stiff conductive polymers like polyaniline (PANI) alternating with poly(acrylic acid) (PAC) are introduced. Preliminary results on their deposition and alignment are given.
The infinitesimal rigid displacement lemma in Lipschitz co‐ordinates and application to shells with minimal regularity
Authors: Anicic Sylvia , Dret Hervé Le , Raoult Annie
Published: May 2004

We establish a version of the infinitesimal rigid displacement lemma in curvilinear Lipschitz co‐ordinates. We give an application to linearly elastic shells whose midsurface and normal vector are both Lipschitz. Copyright © 2004 John Wiley Sons, Ltd.
An operator approach for an oblique derivative boundary‐transmission problem
Authors: Castro L. P. , Santos A. Moura
Published: May 2004

We consider a boundary‐transmission problem for the Helmholtz equation, in a Bessel potential space setting, which arises within the context of wave diffraction theory. The boundary under consideration consists of a strip, and certain conditions are assumed on it in the form of oblique derivatives. Operator theoretical methods are used to deal with the problem and, as a consequence, several convolution type operators are constructed and associated to the problem. At the end, the well‐posedness of the problem is shown for a range of non‐critical regularity orders of the Bessel potential spaces, which include the finite energy norm space. In addition, an operator normalization method is applied to the critical orders case. Copyright © 2004 John Wiley & Sons, Ltd.
Structural assignment of regioisomeric 3‐[2‐ or 5‐anilino‐2‐(alkylamino)phenyl]propanoic acids, 2H‐1,4‐benzothiazin‐3(4H)‐ones and 2,3‐dihydro‐1,5‐benzothiazepin‐4(5H)‐ones by 1D NOE and gHMBC NMR techniques
Authors: Katritzky Alan R. , Akhmedov Novruz G. , Wang Mingyi , Rostek Charles J. , Steel Peter J.
Published: May 2004

The 1H and 13C NMR spectra of compounds 1–11 and 16–22 in CDCl3 and DMSO‐d6 solutions allowed structural assignment to regioisomers 1/5 and 2/6 and their regioselective cyclization products 16–18 utilizing one‐ and two‐dimensional NMR techniques (APT, DEPT, NOE difference, COSY, NOESY, HETCOR and gHMQC, gHMBC). Temperature‐dependent 1H NMR spectra of 8‐anilino‐5‐(4‐methyl‐2‐pentyl)‐2,3‐dihydro‐1,5‐benzothiazepin‐4(5H)‐one (18) indicated a free energy of activation (ΔG‡) of ca 17 kcal mol−1 for interconversion between rotamers. The 1H and 13C NMR spectra of 20 and 22 containing two chiral centers exhibit duplication of several signals, indicating the existence of two diastereomeric forms. The structure of 4 was unambiguously confirmed by x‐ray crystallography. Copyright © 2004 John Wiley & Sons, Ltd.
Acceleration of carbon‐13 spin–lattice relaxation times in amino acids by electrolytes
Authors: Tian Jinping , Yin Yingwu
Published: May 2004

Measurements of the enhancement, by various electrolytes, of the spin–lattice relaxation time of carbon‐13 at different locations in a number of amino acids are reported. Spin–lattice relaxation times T1 of all the carbons in amino acids generally tend to decrease with increase in the concentration of electrolytes, the largest effects often being observed for the charged carboxylate groups of the amino acids. Carboxylic carbons in amino acids are the sensitive ‘acceptor’ of the 13C spin–lattice relaxation accelerating effects offered by electrolytes, and the 13C spin–lattice relaxation accelerating ability of electrolytes decreases in the order Mg(ClO4)2 > MgCl2 > CaCl2 > NaCl > KCl > LiClO4 > NaOH. The mechanisms of the observed phenomena are discussed in terms of intermolecular interaction, paramagnetic impurities in electrolytes and other mechanisms; large contributions of intermolecular interactions with electrolytes are present on complex formation between amino acids and metal ions and the incoming ‘unsaturation’ of the primary solvation shell of cations with the increase in electrolyte concentration. Copyright © 2004 John Wiley & Sons, Ltd.
1H and13C NMR spectral assignments and conformational analysis of 14 19‐nor‐neoclerodane diterpenoids
Authors: Rodríguez Benjamín , Jimeno María L.
Published: May 2004

Unambiguous and complete assignments of1H and13C NMR chemical shifts for 14 19‐nor‐neoclerodane diterpenoids, nine of them isolated from natural sources and five other synthetic derivatives, are presented. The assignments are based on 2D shift‐correlated (1H,1H‐COSY,1H,13C‐gHSQC and1H,13C‐gHMBC) and NOE experiments. The conformations of rings A and B of these compounds are supported by the3J(H,H) values and they agree with the low‐energy conformations obtained by semi‐empirical calculations. Moreover, the data obtained in this work for 2‐acetoxyteucvidin and a semisynthetic 18‐aldehyde derivative indicate that the configuration at C‐2 of the former and at C‐10 of the latter must be reversed with respect to those reported previously. Copyright © 2004 John Wiley & Sons, Ltd.
Reorientational dynamics of p‐sulfonatocalix[4]arene and of its La(III) complex in water
Authors: Israëli Yaël , Facey Glenn A. , Detellier Christian
Published: May 2004

The reorientational dynamics of p‐sulfonatocalix[4]arene and of its La(III) complex in deuterated water were studied by 1H NMR longitudinal relaxation rates. It is shown that the relaxation is purely dipolar in the non‐extreme narrowing regime. The distance between the geminal protons could be determined from the NMR data, giving good agreement with the values generally used in correlation time calculations. The correlation times show an Arrhenius behaviour in good agreement with previously reported data from 13C measurements for a similar uncomplexed calixarene. The Arrhenius energies of activation are identical for the uncomplexed and the complexed calixarenes, suggesting a reorientational motion strongly dependent on the structure of the water cage around the complex. This is also in agreement with a complexation of the La(III) cation in the second sphere of solvation of the sulfonate groups, as shown by molecular dynamics simulations. Copyright © 2004 John Wiley & Sons, Ltd.
Adducts of Rh2[MTPA]4 with some phosphine chalcogenides: nature of binding and ligand exchange
Authors: Gáti Tamás , Simon András , Tóth Gábor , Magiera Damian , Moeller Stefan , Duddeck Helmut
Published: May 2004

Adducts of four phosphine chalcogenides with the chiral dirhodium complex ([RhRh]) were investigated by variable‐temperature 1H and 31P NMR spectroscopy in order to compare their properties as axial ligands. Whereas the selenide (1) and the sulfide (2) are strong ligands with electrostatic attration and, in addition, a significant orbital (HOMO–LUMO) interaction, the phosphine oxide compounds (PO) bind primarily via electrostatic attraction and are relatively weak donors. Moreover, the overall bond strength in these adducts depends on steric congestion around the PO group. Copyright © 2004 John Wiley & Sons, Ltd.
Conformation analysis and molecular mobility of ethylene and tetrafluoroethylene copolymer using solid‐state 19F MAS and 1H → 19F CP/MAS NMR spectroscopy
Authors: Aimi Keitaro , Ando Shinji
Published: May 2004

The changes in the conformation and molecular mobility accompanied by a phase transition in the crystalline domain were analyzed for ethylene (E) and tetrafluoroethylene (TFE) copolymer, ETFE, using variable‐temperature (VT) solid‐state 19F magic angle spinning (MAS) and 1H → 19F cross‐polarization (CP)/MAS NMR spectroscopy. The shifts of the signals for fluorines in TFE units to higher frequency and the continuing decrease and increase in the T1ρF values suggest that conformational exchange motions exist in the crystalline domain between 42 and 145 °C. Quantum chemical calculations of magnetic shielding constants showed that the high‐frequency shift of TFE units should be induced by trans to gauche conformational changes at the CH2CF2 linkage in the E–TFE unit. Although the 19F signals of the crystalline domain are substantially overlapped with those of the amorphous domain at ambient probe temperature (68 °C), they were successfully distinguished by using the dipolar filter and spin‐lock pulse sequences at 145 °C. The dipolar coupling constants for the crystalline domain, which can be estimated by fitting the dipolar oscillation behaviors in the 1H → 19F CP curve, showed a significant decrease with increasing temperature from 42 to 145 °C. This is due to the averaging of 1H19F dipolar interactions originating from the molecular motion in the crystalline domain. The increase in molecular mobility in the crystalline domain was clearly shown by VT T1ρF and 1H → 19F CP measurements in the phase transition temperature range. Copyright © 2004 John Wiley & Sons, Ltd.
NMR characterization of new 10‐membered‐ring macrolactones and dihydrobenzophenazine‐5‐one, oxidized derivatives of benzo[a]phenazines
Authors: Goulart Marília O. F. , Machado Reys José Rui , Emery Flavio S. , Pinto Antônio V. , de Souza Filho José Dias
Published: May 2004

Peroxidation of the phenazine of β‐lapachone using m‐ClC6H4CO3HCH2Cl2 furnished a macrolactone with a rigid 10‐membered ring, and the corresponding N‐oxide, along with a dihydrobenzophenazine‐5‐one. All of the new compounds were fully characterized by spectroscopic methods, with the unambiguous assignment of the hydrogens and carbon NMR signals for the N‐oxide, with the aid of 2‐D NMR, mainly COSY, HMQC, HSQC and HMBC. For the other two compounds some signals could not be assigned owing to their own intrinsic features. Copyright © 2004 John Wiley & Sons, Ltd.
Bilateral intraneural perineurioma presenting as ulnar neuropathy at the elbow
Authors: Beekman Roy , Slooff Willem‐Bart M. , Van Oosterhout Matthijs F. M. , Lammens Martin , Van Den Berg Leonard H.
Published: May 2004

We describe a 36‐year‐old woman with progressive bilateral ulnar neuropathy. Sonographic and magnetic resonance imaging studies revealed extensive focal ulnar nerve enlargement at the elbow. Histological studies gave evidence of an intraneural perineurioma. Because intraneural perineurioma usually appears as a single mass lesion at sites other than typical entrapment sites, this mode of presentation is unusual. We discuss the nature of this benign tumor and the differential diagnosis of nerve enlargement. Knowledge of possible causes of nerve thickening is crucial when performing imaging in patients with neuropathies. Muscle Nerve 30: 239–243, 2004