bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influences of co‐monomers and electrolyte acidity on morphological structure of copper‐in‐copolymer gradient film
Authors: Tang Jianguo , Chen Qiang , Liu Haiyan , Wang Yao 
Published: February 2004

AbstractIn this paper, the influences of composition of copolymers and acidity of electrolyte in an electrochemical reactor on morphological structure of copper‐in‐polymer gradient composite film were investigated. For binary copolymers, poly(acrylonitrile‐co‐methyl acrylate) [P(AN‐co‐MA)] and poly(acrylonitrile‐co‐sodium allyl sulfonate) [P(AN‐co‐SAS)], the charged group SO in P(AN‐co‐SAS) improves the swelling of the copolymer phase and copper reduction to form gradient morphology; the carboxylic ester group in P(AN‐co‐MA) is not effective because of its poor hydrophilicity, but it is a cooperating component with P(AN‐co‐SAS) to avoid excess of counterion (i.e., Na+) in SCF, which might severely interrupt Cu2+ coexistence. The swelling of the polymer phase is helpful to decrease the energy of the transfer ions in SCF and to enhance copper deposition and gradient formation. The increase of surface energy because of cluster growth raises the surface energy level of deposited Cu0 clusters. The conteraction between these two energy factors allows the size of clusters to be 50–100 nm. The appropriate H+ concentration improves active Cu2+ reduction and thus deposited gradient copper phase in the copolymer matrix. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 373–380, 2004
Proliferation rate of fibroblast cells on polyethylene surfaces with wettability gradient
Authors: Choee Jong‐Hwa , Lee Sang Jin , Lee Young Moo , Rhee John Moon , Lee Hai Bang , Khang Gilson 
Published: February 2004

AbstractSurface wettability on anchorage‐dependent cells has an important role in cell growth rate. In our previous studies, we prepared a wettability gradient on polyethylene (PE) surfaces using corona discharge treatment from a knife‐type electrode whose power increased gradually along the sample length. The PE surfaces were oxidized gradually with increasing power and characterized by Fourier transform infrared spectroscopy, contact angle goniometry, and electron spectroscopy for chemical analysis. The purpose of this study is to determine the rate of proliferation on polymer surfaces with different wettability. The behavior of cell growth for NIH/3T3 fibroblast cells attached on the polymer surfaces with different hydrophilicity was investigated using wettability gradient PE surfaces prepared by corona discharge treatment. They were investigated for the number of grown cells from 24 to 60 h in terms of surface wettability. From the slope of cell number on PE gradient surface versus culture time, the proliferation rates (number of cell/cm2 · h) were calculated. It was observed that the proliferation rate was increased more on positions with moderate hydrophilicity of the wettability gradient surface than on the more hydrophobic or hydrophilic positions, i.e., 1111 (number of cell/cm2 · h) of 57° of water contact angle at the 2.5‐cm position (P < 0.05). This result seems closely related to the serum protein adsorption on the surface: the serum proteins were also adsorbed more on the moderately hydrophilic surface. In conclusion, surface wettability plays an important role in cell adhesion, spreading, and proliferation on the polymer surfaces. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 599–606, 2004
Effect of the Secondary Structure of Carbohydrate Residues of α1‐Acid Glycoprotein (Orosomucoid) on the Local Dynamics of Trp Residues
Authors: Albani Jihad René 
Published: February 2004

AbstractWe studied in this work the relation between the secondary structure of the carbohydrate residues of α1‐acid glycoprotein and the local motions of Trp residues of the protein. We measured for this purpose the fluorescence emission intensity and anisotropy of the Trp residues between −46 and +30° of the sialylated and asialylated protein. Our results indicate that, in both forms, the global profile of the emission intensity with temperature shows that Trp residues display static and collisional interaction with the neighboring amino acids. However, the profile of the asialylated form is more structured than that observed for the sialylated protein. The Y‐plot analysis of the emission‐anisotropy results indicated that the frictional resistance to rotation of the surface Trp residue is less important in the sialylated protein than in the asialylated form. This result is in good agreement with the fact that, in the asialylated conformation, the carbohydrate residues are closer to the protein surface than in the sialylated form, thereby increasing the contact of the surface Trp residue with the neighboring amino acids. Also, the interaction between the carbohydrate residues and the surface Trp residue contributes to the modification of the frictional resistance to rotation of the fluorophore.
Polarized Vesicles in Molecular Recognition and Catalysis
Authors: Sakai Naomi , Matile Stefan 
Published: February 2004

AbstractThis account summarizes studies on chemistry in polarized vesicles with rigid‐rod molecules. Examples for the recognition of and self‐assembly, molecular recognition, and catalysis in polarized vesicles are discussed with emphasis on ‘remote control’ by dipolepotential interactions and electrostatic steering.
Cyclopropane‐Annelated Azaoligoheterocycles by Ti‐Mediated Intramolecular Reductive Cyclopropanation of Cyclic Amino Acid Amides
Authors: Gensini Martina , de Meijere Armin 
Published: February 2004

AbstractStarting from pyrrole‐ and indole‐2‐carboxylic acids 5 a and 5 b, the tri‐ and tetracyclic N,N‐dibenzylcyclopropylamines 7 a and 7 b have been synthesized in 52 and 33 % overall yield, respectively. The synthesis of the enantiopure tetracyclic diamine 10 has been achieved applying the established set of reactions to N‐tert‐butoxycarbonylindoline‐2‐carboxylic acid (8) in 46 % overall yield. The amide 15 could not be prepared in the same way starting from the N‐tert‐butoxycarbonylproline 11. In fact, in the allylation step the stereogenic center was deprotonated and the doubly alkylated amide 13 was formed. However, the desired intermediate 15 could be obtained from L‐proline in 49 % yield performing first the N‐allylation step, then the introduction of the amide function. From 15, the cyclopropane‐annelated pyrrolizidine 16 was obtained in 70 % yield as a mixture of (1aS,6aS,6bR)‐16 and (1aR,6aS,6bS)‐16 diastereoisomers in a ratio of 1:2.9.
Heteronuclear Rhodium, Palladium, Platinum, and Gold Organoimido Complexes from Dinuclear Organoamido Rhodium Precursors
Authors: Oro Luis A. , Ciriano Miguel A. , Tejel Cristina , Bordonaba Marta , Graiff Claudia , Tiripicchio Antonio 
Published: February 2004

AbstractTreatment of the organoamido complexes [Rh2(μ‐4‐HNC6H4Me)2(L2)2] (L2 = 1,5‐cyclooctadiene (cod), L = CO) with nBuLi gave solutions of the organoimido species [Li2Rh2(μ‐4‐NC6H4Me)2(L2)2]. Further reaction of [Li2Rh2(μ‐4‐NC6H4Me)2(cod)2] with [Rh2(μ‐Cl)2(cod)2] afforded the neutral tetranuclear complex [Rh4(μ‐4‐NC6H4Me)2(cod)4] (2), which rationalizes the direct syntheses of 2 from [Rh2(μ‐Cl)2(cod)2] and Li2NC6H4Me. Reactions of [Li2Rh2(μ‐4‐NC6H4Me)2(CO)4] with chloro complexes such as [Rh2(μ‐Cl)2(CO)4], [MCl2(cod)] (M = Pd, Pt), and [Ru2(μ‐Cl)2Cl2(p‐cymene)2] afforded the homo‐ and heterotrinuclear complexes PPN[Rh3(μ‐4‐NC6H4Me)2(CO)6] (5; PPN=bis(triphenylphosphine)iminium), [(CO)4Rh2(μ‐4‐NC6H4Me)2M(cod)] (M = Pd (6), Pt(7)) and [(CO)4Rh2(μ‐4‐NC6H4Me)2Ru(p‐cymene)] (8), while the reaction with [AuCl(PPh3)] gave the tetranuclear compound [(CO)4Rh2(μ‐4‐NC6H4Me)2{Au(PPh3)}2] (9). The structures of complexes 6, 8, and 9 were determined by X‐ray diffraction studies. The anion of 5 reacts with [AuCl(PPh3)] to give the butterfly cluster [{Rh3(μ‐4‐NC6H4Me)2(CO)6}Au(PPh3)] (10), in which the Au atom is bonded to two rhodium atoms. Reaction of the anion of 5 with [Rh(cod)(NCMe)2](BF4) gave the tetranuclear complex [Rh4(μ‐4‐NC6H4Me)2(CO)6(cod)] (11) in which the Rh(cod) fragment is π‐bonded to one of the arene rings, while the reaction of the anion of 5 with [PdCl2(cod)] afforded the heterotrinuclear complex 6 through a metal exchange process.
α,α‐Disubstituted Glycines Bearing a Large Hydrocarbon Ring: Peptide Self‐Assembly through Hydrophobic Recognition
Authors: Ohwada Tomohiko , Kojima Daisuke , Kiwada Tatsuto , Futaki Shiroh , Sugiura Yukio , Yamaguchi Kentaro , Nishi Yoshinori , Kobayashi Yuji 
Published: February 2004

AbstractA method was developed for synthesizing α,α‐disubstituted glycine residues bearing a large (more than 15‐membered) hydrophobic ring. The ring‐closing metathesis reactions of the dialkenylated malonate precursors proceed efficiently, particularly when long methylene chains tether both terminal olefin groups. Surprisingly, the amino groups of these α,α‐disubstituted glycines are inert to conventional protective reactions (e.g., N‐tert‐butoxycarbonyl (Boc) protection: Boc2O/4‐dimethylaminopyridine (DMAP)/CH2Cl2; N‐benzyloxycarbonyl (Z) protection: Z‐Cl/DMAP/CH2Cl2). Curtius rearrangement of the carboxylic acid functionality of the malonate derivative after ring‐closing metathesis leads to formation of an amine functionality and can be catalyzed by diphenylphosphoryl azide. However, only the intermediate isocyanates can be isolated, even in the presence of alcohols such as benzyl alcohol. The isocyanates obtained by Curtius rearrangement in an aprotic solvent (benzene) were isolated in high yields and treated with 9‐fluorenylmethanol in a high‐boiling‐point solvent (toluene) under reflux to give the N‐9‐fluorenylmethoxycarbonyl (Fmoc)‐protected aminomalonate derivatives in high yield. These hydrophobic amino acids can be incorporated into a peptide by Fmoc solid‐phase peptide synthesis and the acid fluoride activation method. The stability of the monomeric α‐helical structure of a 17‐amino‐acid peptide was enhanced by replacement of two alanine residues with two hydrophobic amino acid residues bearing a cyclic 18‐membered ring. The results of sedimentation equilibrium studies suggested that the peptide assembles into hexamers in the presence of 100 mM NaCl.
Experimentelle Untersuchung und Modellierung der Löslichkeit von Kalkstein und Gips bei höheren Ionenstärken – Teil 2: Einfluss von Carbonsäuren
Authors: Loos D. , Pasel C. , Luckas M. , Schmidt K.G. , Herbell J.‐D. 
Published: February 2004

AbstractNo abstracts.
Measurement of online visibility and its impact on Internet traffic
Authors: Drèze Xavier , Zufryden Fred 
Published: February 2004

The Internet landscape is an increasingly crowded space where hundreds of thousands of companies are fighting for attention. Some of these companies are universally known (Yahoo!, Amazon) while others are more obscure (Literary Guild, Just Say Wow). Regardless of their level of Internet presence, all these companies are interested in improving their position, particularly now that managers are asked to justify their online activities. To help managers assess their online presence, and give them a way to compare their position relative to their competitors, this article aims to develop a measure of a company's online visibility. Moreover, this study seeks to understand what factors drive online visibility, and how. The visibility measure we develop captures the extent to which a user is likely to come across an online reference to a company's Web site. It is based on data collected from multiple sources that include search engine results, Web-site contents, and online directory listings. It is calibrated using a large-scale telephone survey, and is validated using data obtained from Web crawlers and Internet consumer-panel sources. In the latter part of the article, we show how managers can use the visibility measure to compare the online presence of their company to their competitors’. We also show how they can use this information to perform scenario analysis aimed at finding the best way to improve their online position.
Activation requirements for the induction of CD4+CD25+ T cell suppressor function
Authors: Thornton Angela M. , Piccirillo Ciriaco A. , Shevach Ethan M. 
Published: February 2004

AbstractThe in vivo differentiation/survival of CD4+CD25+ T suppressor cells is dependent on IL‐2 and CD28‐mediated costimulatory signals. To determine the cytokine and costimulatory requirements for CD25+ T cells in vitro, we established a two‐stage culture system where CD25+ T cells were activated in a primary culture. In the subsequent culture, activated CD4+CD25+ cells were then mixed with responders in order to assess their suppressor function. Pre‐culture of CD25+ T cells with anti‐CD3 alone resulted in poor survival and minimal induction of suppressor activity. Pre‐culture in the presence of anti‐CD3 and IL‐2 or IL‐4, but not IL‐6, IL‐7, IL‐9, IL‐10 or IL‐15, resulted in proliferation of the CD25+ cells and induction of potent suppressor function. Inhibition of the interaction of CD28 or cytotoxic T lymphocyte‐associated antigen‐4 (CTLA‐4) with CD80/CD86 in the pre‐culture of CD4+CD25+ cells did not prevent the induction of suppressor function. Furthermore, the inhibition of costimulatory signals did not inhibit the ability of fresh CD25+ T cells to inhibit CD8+ responders under conditions where activation of the responders was independent of CD80/CD86. These studies support the view that activation of CD25+ T cells requires IL‐2/IL‐4 for their survival/differentiation into effector cells, but is independent of CD28/CTLA‐4‐mediated costimulation.
SMUCKLER/TIM4 is a distinct member of TIM family expressed by stromal cells of secondary lymphoid tissues and associated with lymphotoxin signaling
Authors: Shakhov Alexander N. , Rybtsov Stanislav , Tumanov Alexei V. , Shulenin Sergey , Dean Michael , Kuprash Dmitry V. , Nedospasov Sergei A. 
Published: February 2004

AbstractLymphotoxin‐α (LTα) was originally linked to delayed‐type hypersensitivity and its production was later attributed to Th1, but not Th2 cells. Studies employing knockout mice demonstrated that LT signaling is essential for the development and functional compartmentalization of lymphoid tissues. Here, using gene expression profiling, we identified a novel gene termed SMUCKLER (spleen, mucin‐containing, knockout of lymphotoxin), that is selectively down‐regulated in spleens of LTα‐ or LTβ‐deficient mice. The encoded transmembrane protein contains immunoglobulin V and mucin domains and is identical to TIM4, a predicted member of recently identified TIM family (T cell immunoglobulin‐ and mucin‐domain‐containing molecule). Unlike TIM1 and TIM3, which were implicatedin T cell‐mediated functions, SMUCKLER lacks tyrosine phosphorylation motif in its intracellular domain and is not expressed by bone marrow‐derived cells. In situ hybridization of spleen sections demonstrated SMUCKLER expression by stromal cells predominantly in the marginal zone and to a lesser extent throughout the white pulp. Similarly to other TIM genes, SMUCKLER maps to a locus associated with predisposition to asthma both in mice and in humans (11.b1 and 5q33, respectively) and shows coding sequence variations between BALB/c and DBA mice. Therefore, SMUCKLER/TIM4 may be considered as a candidate disease‐predisposition gene for asthma.
Identification of pro‐interleukin 16 as a novel target of MAP kinases in activated T lymphocytes
Authors: Laurence Arian , Astoul Emmanuelle , Hanrahan Sarah , Totty Nick , Cantrell Doreen 
Published: February 2004

AbstractT lymphocyte activation is controlled by a coordinated web of tyrosine and serine kinases. There is a large body of information about tyrosine kinase substrates in T cells but analysis of serine kinase substrates has been more difficult. Recently we described an antiserum that recognizes serine‐phosphorylated peptides corresponding to the substrate sequences for AGC serine kinases. This antiserum, termed PAP‐1 (phospho antibody for proteomics‐1), has proven useful for probing the serine phosphoproteome of antigen receptor‐activated T lymphocytes. The present study shows that PAP‐1 can also be used to explore serine kinases activated by cytokines and chemokines in T cells. Using PAP‐1, together with proteomic analysis, the precursor form of the cytokine IL‐16 (ProIL‐16) was shown to be phosphorylated on Ser144 in antigen receptor‐, SDF1α‐ and IL‐2‐activated T cells. Genetic and pharmacological‐inhibitor experiments showed that the phosphorylation of ProIL‐16 is dependent on activation of the kinases Erk1/2. IL‐16 is secreted by mitogen‐activated T cells, and the biochemical link between ProIL‐16 and Erk1/2, revealed by studies with PAP‐1, prompted analysis of the role of MAP kinases in this response. We show that TCR‐mediated secretion of IL‐16 is dependent on MAP kinases. The present study thus reveals how phosphoproteomic analysis opens previously unrecognized avenues for research, and yields novel insights about targets for MAP kinases in T lymphocytes.
Immunoglobulin gene conversion in chicken DT40 cells largely proceeds through an abasic site intermediate generated by excision of the uracil produced by AID‐mediated deoxycytidine deamination
Authors: Noia Javier M. Di , Neuberger Michael S. 
Published: February 2004

AbstractDiversification of the primary antibody repertoire in chickens is achieved by a gene conversion process that uses a set of immunoglobulin variable (IgV) pseudogenes as templates. Studies usingthe chicken DT40 B lymphoma cell line have shown that this gene conversion is dependent on activation‐induced deaminase, which deaminates deoxycytidine to deoxyuridine in the IgV gene. The mechanism by which the resultant deoxyuridine/deoxyguanosine (dU/dG) mismatch acts to initiate the gene conversion process is unknown but likely involves either (i) recognition of the dU/dG pair by the mismatch repair complex or (ii) recognition of the dU itself by uracil‐DNA glycosylase. To discriminate these possibilities, we have investigated the effects on IgV gene conversion of inhibiting uracil‐DNA glycosylase. We find that such inhibition diminishes gene conversion, biasing instead towards point mutations. These results demonstrate that IgV gene conversion in DT40 cells is substantially dependent on uracil excision and implies that it proceeds by a pathway involving an abasic site, which could be acted upon by an apyrimidinic endonuclease to generate a DNA strand break facilitating the conversion process.
Phage‐displayed libraries of peptide/major histocompatibility complexes
Authors: Dogan Ismail , Dorgham Karim , Chang Hsiu‐Ching , Parizot Christophe , Lemaître Fabrice , Ferradini Laurent , Reinherz Ellis L. , Debré Patrice , Gorochov Guy 
Published: February 2004

AbstractCharacterizing peptide epitopes targeted by major histocompatibility complex (MHC)‐restricted T cells of unknown specificity would have broad implications. In this article we introduce and validate an original phage‐displayed library of noncovalent complexes of peptide and MHC (P/MHC). We show that soluble MHC molecules associate with peptides presented by a phage, thereby resulting in the formation of multivalent P/MHC phages. Complex formation is stabilized by the interaction of the soluble partner (MHC) with two components, peptide and β2‐microglobulin, both of which are covalently linked to the phage. As proof of concept, we have used this strategy to express peptide libraries in the context of H‐2Kb. Using monoclonal antibody 25D (specific for ovalbumin/H‐2Kb) as a template to screen the library, we were able to select a variant epitope functionally and structurally related to the wild‐type peptide. Interaction studies between monoclonal antibody 25D and cells suggest that the variant peptide has been selected on the basis of a decreased dissociation rate between the peptide/H‐2Kb complex and its ligand. A weak agonist of the N15 TCR (vesicular stomatitis virus/H‐2Kb‐specific) was also isolated from another P/MHC library. This strategy opens up new perspectives for antigen discovery and the manipulation of T cell responses.
Synthesis of Nitrogen‐Containing Spiro Compounds from Lactams by Allylboration and Subsequent Ring‐Closing Metathesis
Authors: Nieczypor Piotr , Mol Johannes C. , Bespalova Natalia B. , Bubnov Yuri N. 
Published: February 2004

AbstractA series of nitrogen‐containing spiro[4.n]alkenes was prepared with excellent yields starting from lactams in two steps: allylboration on the carbonyl carbon and subsequent ring‐closing metathesis of the 2,2‐diallyl N‐heterocycles. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
An Efficient Route for the Synthesis of New Analogues of Polyaminocarboxylic Acid Incorporating O, N, and S Atoms
Authors: Gouin Sébastien G. , Benoist Eric , Gestin Jean‐François , Meslin Jean Claude , Deniaud David 
Published: February 2004

AbstractWe have synthesised three rigid polycarboxylated hexadentate ligands that differ only in the nature of their heteroatom, either oxygen (1), nitrogen (2), or sulfur (3). These compounds were obtained in four or five steps from substituted orthoanilines after protection/deprotection sequences. An aromatic backbone was chosen to stiffen the structure of the ligands and, thus, facilitate complexation (preorganization concept). A preliminary chelation test revealed a marked selectivity of the nitrogen‐containing ligand for indium‐111. In accordance with the hard and soft acid and base (HSAB) theory, the choice of ligand should result in notable differences in behaviour during complexation and, thus, augment selectivity with regard to the metal. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Exclusive β‐Substitution in the Reaction of Octafluoronaphthalene with Secondary Amines
Authors: Sorokin Vladimir I. , Ozeryanskii Valery A. , Pozharskii Alexander F. 
Published: February 2004

AbstractThe reaction between octafluoronaphthalene and dimethylamine, pyrrolidine or piperidine in DMF, dimethyl(ethylene)urea (DMEU) or without solvent leads to the exclusive substitution of β‐fluorine atoms giving naphthalene derivatives with four NR2 groups. This was proved by 19F NMR of the products and a crystal structure determination for 1,4,5,8‐tetrafluoro‐2,3,6,7‐tetrakis(piperidin‐1‐yl)naphthalene. The main feature of the reaction in DMF was a transamidation process. The remaining four fluorine atoms in the synthesised tetraamines could be smoothly replaced by reduction with LiAlH4. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Synthesis of Peptide‐PNA‐Peptide Conjugates by Semi‐Solid‐Phase Chemical Ligation Combined with Deactivation/Capture of Excess Reactants
Authors: de Koning Martijn C. , Filippov Dmitri V. , van der Marel Gijsbert A. , van Boom Jacques H. , Overhand Mark 
Published: February 2004

AbstractAn expeditious route to peptide‐PNA‐peptide conjugates following a two‐step native chemical ligation (NCL) strategy is described. A cys‐PNA‐thioester is immobilized on PEGA‐aldehyde resin by thiazolidine formation, followed by capping of excess resin aldehydes. The first NCL reaction is then performed with the immobilized PNA‐thioester, to give, after release from the solid support, the cys‐PNA‐peptide intermediate with relatively high purity. The latter is then converted into the target compound by the second NCL reaction with a thioester peptide, the excess of which is captured using a cysteine‐PEGA resin. The resulting peptide‐PNA‐peptide can then be readily isolated by a simple purification step. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)