bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural malleability of plasticins: Preorganized conformations in solution and relevance for antimicrobial activity
Authors: Bruston F. , Lacombe C. , Zimmermann K. , Piesse C. , Nicolas P. , El Amri C. 
Published: February 2007

AbstractPlasticins (23 long‐residue glycine‐leucine‐rich dermaseptin‐related peptides produced by the skin of South American hylids) have very similar amino acid sequences, hydrophobicities, and amphipathicities, but differ in their membrane‐damaging properties and structurations (i.e. destabilized helix states, β‐hairpin, β‐sheet, and disordered states) at anionic and zwitterionic membrane interfaces. Structural malleability of plasticins in aqueous solutions together with parameters that may govern their ability to fold within β‐hairpin like structures were analyzed through circular dichroism and FTIR spectroscopic studies completed by molecular dynamics simulations in polar mimetic media. The goal of this study was to probe to which extent pre‐existent peptide conformations, i.e. intrinsic “conformational landscape”, may be responsible for variability in bioactive conformation and antimicrobial/hemolytic mechanisms of action of these peptides in relation with their various membrane disturbing properties. All plasticins present a turn region that does not always result in folding into a β‐hairpin shaped conformation. Residue at position 8 plays a major role in initiating the folding, while position 12 is not critical. Conformational stability has no major impact on antimicrobial efficacy. However, preformed β‐hairpin in solution may act as a conformational lock that prevents switch to α‐helical structure. This lock lowers the antimicrobial efficiency and explains subtle differences in potencies of the most active antimicrobial plasticins. © 2007 Wiley Periodicals, Inc. Biopolymers 86: 42–56, 2007.This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Hydrodynamic stress induces monoterpenoid oxindole alkaloid accumulation by Uncaria tomentosa (Willd) D. C. cell suspension cultures via oxidative burst
Authors: Trejo‐Tapia Gabriela , Sepúlveda‐Jiménez Gabriela , Trejo‐Espino José Luis , Cerda‐García‐Rojas Carlos M. , de la Torre Mayra , Rodríguez‐Monroy Mario , Ramos‐Valdivia Ana C. 
Published: February 2007

AbstractUncaria tomentosa cell suspension cultures were grown in a 2‐L stirred tank bioreactor operating at a shear rate $\dot \gamma _{\rm avg} = 86\,{\rm s}^{ - 1} $. The cultures showed an early monophasic oxidative burst measured as H2O2 production (2.15 µmol H2O2 g−1 dw). This response was followed by a transient production of monoterpenoid oxindole alkaloids (178 ± 40 µg L−1 at 24 h). At the stationary phase (144 h), the increase of the shear rate $\dot \gamma _{{\rm avg}} $ up to 150 s−1 and/or oxygen tension up to 85% generated H2O2, restoring oxindole alkaloid production. U. tomentosa cells cultured in Erlenmeyer flasks also exhibited the monophasic oxidative burst but the H2O2 production was 16‐fold lower and the alkaloids were not detected. These cells exposed to H2O2 generated in situ produced oxindole alkaloids reaching a maximum of 234 ± 40 µg L−1. A positive correlation was observed between the oxindole alkaloid production and the endogenous H2O2 level. On the other hand, addition of 1 µM diphenyleneiodonium (NAD(P)H oxidase inhibitor) or 10 µM sodium azide (peroxidases inhibitor) reduced both H2O2 production and oxindole alkaloids build up, suggesting that these enzymes might play a role in the oxidative burst induced by the hydrodynamic stress. Biotechnol. Bioeng. 2007; 98: 230–238. © 2007 Wiley Periodicals, Inc.
Comparative Experimental and EXAFS Studies in the Mizoroki–Heck Reaction with Heteroatom‐Functionalised N‐Heterocyclic Carbene Palladium Catalysts
Authors: Fiddy Steven G. , Evans John , Neisius Thomas , Newton Mark A. , Tsoureas Nikolaos , Tulloch Arran A. D. , Danopoulos Andreas A. 
Published: February 2007

AbstractA study on the Mizoroki–Heck coupling of selected aryl bromides with acrylates catalysed by a series of Pd complexes of bidentate pyridyl‐, picolyl‐, diphenylphosphinoethyl‐ and diphenylphosphinomethyl‐functionalised N‐heterocyclic carbene (NHC) is reported. The observed activity is dependent on the type of solvent and base used and the nature of the “classical” donors of the mixed‐donor bidentate ligand and its bite angle. A mechanistic model is presented for the pyridine‐functionalised NHC complexes based on an in situ EXAFS study under dilute catalyst conditions (2 mM Pd). The model involves pre‐dissociation of the pyridine functionality and oxidative addition of ArBr in the early stages of the reaction, as well as formation of monomeric and dimeric Pd species at the time of substrate conversion.
QM/MM Modeling of Enantioselective Pybox–Ruthenium‐ and Box–Copper‐Catalyzed Cyclopropanation Reactions: Scope, Performance, and Applications to Ligand Design
Authors: García José I. , Jiménez‐Osés Gonzalo , Martínez‐Merino Víctor , Mayoral José A. , Pires Elísabet , Villalba Isabel 
Published: February 2007

AbstractAn extensive comparison of full‐QM (B3LYP) and QM/MM (B3LYP:UFF) levels of theory has been made for two enantioselective catalytic systems, namely, Pybox–Ru and Box–Cu complexes, in the cyclopropanation of alkenes (ethylene and styrene) with methyl diazoacetate. The geometries of the key reaction intermediates and transition structures calculated at the QM/MM level are generally in satisfactory agreement with full‐QM calculated geometries. More importantly, the relative energies calculated at the QM/MM level are in good agreement with those calculated at the full‐QM level in all cases. Furthermore, the QM/MM energies are often in better agreement with the stereoselectivity experimentally observed, and this suggests that QM/MM calculations can be superior to full‐QM calculations when subtle differences in inter‐ and intramolecular interactions are important in determining the selectivity, as is the case in enantioselective catalysis. The predictive value of the model presented is validated by the explanation of the unusual enantioselectivity behavior exhibited by a new bis‐oxazoline ligand, the stereogenic centers of which are quaternary carbon atoms.
A Combinatorial Approach to the Discovery of Biocidal Six‐Residue Cyclic d,l‐α‐Peptides Against the Bacteria Methicillin‐Resistant Staphylococcus aureus (MRSA) and E. coli and the Biofouling Algae Ulva linza and Navicula perminuta
Authors: Fletcher James T. , Finlay John A. , Callow Maureen E. , Callow James A. , Ghadiri M. Reza 
Published: February 2007

AbstractA combinatorial approach has been used to rapidly identify cyclic d,l‐α‐peptide hexamer sequences that exert biocidal activity towards both methicillin‐resistant Staphylococcus aureus (MRSA) and E. coli bacteria, as well as the marine algae Ulva linza and Navicula perminuta. Evaluation of the effects against marine algae was facilitated by the development of a reliable, automated assay for toxicity, which should be of general utility for biofouling investigations. While the selective toxicity of cyclic d,l‐α‐peptides towards bacteria has been proven to be highly sensitive to minor changes in amino acid composition, this study demonstrates that this phenomenon extends to eukaryotic species as well, despite their significant structural differences. In performing toxicity assays on both prokaryotic and eukaryotic organisms in parallel, we have discovered examples of six‐residue cyclic d,l‐α‐peptide sequences with either broad‐spectrum or highly selective biocidal activities. Sequence [KWFFFH] (underlined amino acid abbreviations represent D‐amino acid residues) was found to display 100‐fold selectivity towards U. linza, demonstrating that the approach described herein may help lead to the development of new biofouling tools which are not generally toxic to all organisms, but rather specifically target microbial agents of interest.
Property Tuning in Charge‐Transfer Chromophores by Systematic Modulation of the Spacer between Donor and Acceptor
Authors: Bureš Filip , Schweizer W. Bernd , May Joshua C. , Boudon Corinne , Gisselbrecht Jean‐Paul , Gross Maurice , Biaggio Ivan , Diederich François 
Published: February 2007

AbstractA series of donor–acceptor chromophores was prepared in which the spacer separating 4‐dimethylanilino (DMA) donor and C(CN)2 acceptor moieties is systematically varied. All of the new push–pull systems, except 4 b, are thermally stable molecules. In series a, the DMA rings are directly attached to the central spacer, whereas in series b additional acetylene moieties are inserted. X‐ray crystal structures were obtained for seven of the new, intensely colored target compounds. In series a, the DMA rings are sterically forced out of the mean plane of the residual π system, whereas the entire conjugated π system in series b is nearly planar. Support for strong donor–acceptor interactions was obtained through evaluation of the quinoid character of the DMA ring and by NMR and IR spectroscopy. The UV/Vis spectra feature bathochromically shifted, intense charge‐transfer bands, with the lowest energy transitions and the smallest optical gap being measured for the two‐dimensionally extended chromophores 6 a and 6 b. The redox behavior of the push–pull molecules was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). In the series 1 b, 2 b, 4 b, 5 b, in which the spacer between donor and acceptor moieties is systematically enlarged, the electrochemical gap decreases steadily from 1.94 V (1 b) to 1.53 V (5 b). This decrease is shown to be a consequence of a reduction in the D–A conjugation with increasing spacer length. Degenerate four‐wave mixing experiments reveal high third‐order optical nonlinearities, pointing to potentially interesting applications of some of the new chromophores in optoelectronic devices.
Phenylboronate 160Tb complexes for molecular recognition of glycoproteins expressed on tumor cells
Authors: Djanashvili Kristina , Koning Gerben A. , van der Meer Astrid J.G.M. , Wolterbeek Hubert Th. , Peters Joop A. 
Published: February 2007

AbstractThe over‐expression of sialic acid on the surface of cancer cells compared with normal ones makes this nine‐carbon sugar an attractive biomarker for molecular diagnosis and therapy. Here, we describe a study on the molecular recognition of sialic acid end groups on the surface of human glioma cells by 160Tb–DTPA–EN2, 160Tb–DTPA–(ENPBA)2 and 160Tb–DTPA–(PBA)2 complexes. The results show Tb–DTPA–(ENPBA)2 to be the most efficient targeting agent, due to the electrostatic interaction between its two positively charged ammonium groups and the negatively charged cell surface, which provides an additional stabilization of the covalent binding through the PBA moieties and the sialic acid diol functions. Up to 5.5 nmol Tb/mg protein is taken up by the cells. ICP analysis after incubation experiments with non‐radioactive Tb–DTPA–(ENPBA)2 suggests that dissociation of Tb from this complex occurs after its binding to the cell surface. Most likely, most of the free Tb remains adsorbed on the surface of the cells, although internalization of a small amount cannot be excluded. Copyright © 2007 John Wiley & Sons, Ltd.
Psychometric properties of the eating disorder examination‐questionnaire: Factor structure and internal consistency
Authors: Peterson Carol B. , Crosby Ross D. , Wonderlich Stephen A. , Joiner Thomas , Crow Scott J. , Mitchell James E. , Bardone‐Cone Anna M. , Klein Marjorie , le Grange Daniel 
Published: February 2007

AbstractObjective:The purpose of this investigation was to evaluate the factor structure and the internal consistency of the Eating Disorder Examination‐Questionnaire (EDE‐Q).Method:The EDE‐Q was administered to 203 women with bulimic symptoms, who were recruited from five Midwestern communities.Results:Acceptable levels of internal consistency were observed for the EDE‐Q total score (α = .90) and subscales: Restraint (α = .70), Eating Concern (α = 0.73), Shape Concern (α = 0.83) and Weight Concern (α = 0.72). Exploratory factor loadings using Principal Axis Analysis supported the Eating Concern and Restraint subscales. Most of the Shape Concern and Weight Concern items loaded on one factor, with the exception of the items focusing on the importance of weight and shape in self‐evaluation and preoccupation with shape and weight.Conclusion:The results of this study provide support for the internal consistency of the EDE‐Q and indicate a need for further examination of the factor structure of this instrument. © 2007 by Wiley Periodicals, Inc. Int J Eat Disord 2007
Expression of IL‐10 in Th memory lymphocytes is conditional on IL‐12 or IL‐4, unless the IL‐10 gene is imprinted by GATA‐3
Authors: Chang Hyun‐Dong , Helbig Christina , Tykocinski Lars , Kreher Stephan , Koeck Juliana , Niesner Uwe , Radbruch Andreas 
Published: February 2007

AbstractIn Th1 and Th2 memory lymphocytes, the genes for the cytokines interleukin (IL)‐4 and interferon‐γ (IFN‐γ) are imprinted for expression upon restimulation. This cytokine memory is based on expression of the transcription factors T‐bet for IFN‐γ, and GATA‐3 for IL‐4, and epigenetic modification of the cytokine genes. In Th2 cells, expression of the cytokine IL‐10 is also induced by GATA‐3. Here, we show that this induction is initially not accompanied by epigenetic modification of the IL‐10 gene. Only after repeated restimulation of a memory Th2 cell in the presence of IL‐4, extensive histone acetylation of the IL‐10 gene is detectable. This epigenetic imprinting correlates with the development of a memory for IL‐10 in repeatedly restimulated Th2 cells. In Th1 cells, IL‐10 expression is induced by IL‐12, but the IL‐10 gene lacks detectable histone acetylation. Accordingly, IL‐10 expression in restimulated memory Th1 cells remains conditional on the presence of IL‐12. This finding defines a potential anti‐inflammatory role for IL‐12 in Th1 recall responses. While in primary Th1 responses IL‐12 is required to induce expression of the pro‐inflammatory cytokine IFN‐γ, in secondary Th1 responses IFN‐γ re‐expression is independent of IL‐12, which still is able to induce expression of the anti‐inflammatory cytokine IL‐10.
IL‐4 depletion enhances host resistance and passive IgA protection against tuberculosis infection in BALB/c mice
Authors: Buccheri Simona , Reljic Rajko , Caccamo Nadia , Ivanyi Juraj , Singh Mahavir , Salerno Alfredo , Dieli Francesco 
Published: February 2007

AbstractThe influence of Th2 cytokines in tuberculosis has been a matter of dispute. Here we report that IL‐4 has a profound regulatory effect on the infection of BALB/c mice with Mycobacterium tuberculosis. Depletion of IL‐4 with a neutralizing mAb caused only evanescent reduction of lung infection, but when combined with i.n. inoculations of IgA anti‐mycobacterial α‐crystallin mAb and mouse rIFN‐γ, we observed a 40‐fold reduction of the bacterial counts in the lungs at 3 wks following i.n. infection (p<0.001). In genetically deficient IL‐4–/– BALB/c mice, infection in both lung and spleen was substantially reduced for up to 8 wks without further treatment. Reconstitution of IL‐4–/– mice with rIL‐4 increased bacterial counts to wild‐type levels and made the mice refractory to protection by IgA/IFN‐γ. Analysis of the lungs showed increased granulomatous infiltration and proinflammatory mediators in anti‐IL‐4/IgA/IFN‐γ‐treated and infected mice. We conclude that the action of IL‐4 in tuberculosis is targeted at macrophages and that it may include an antagonistic effect on their IgA/IFN‐γ‐induced activation and nitric oxide production. The described novel immunotherapy, combining treatments with anti‐IL‐4, IgA antibody and IFN‐γ, has potential for translation toward the passive immunoprophylaxis of tuberculosis.
Multispecific responses by T cells expanded by endogenous self‐peptide/MHC complexes
Authors: Cai Guifang , Hafler David A. 
Published: February 2007

AbstractThe paradox of autoreactivity to self‐peptides in physiological as opposed to pathological immune responses is not well understood. Here, we directly examined the human T cell response to endogenous self‐peptides in a series of healthy subjects. CFSE‐labeled T cells were stimulated with unmanipulated antigen‐presenting cells containing endogenous self‐antigen, and the resulting CD4+ populations entering into cell cycle (CFSElow) or non‐proliferating CD4+ cells (CFSEhigh) were single‐cell sorted, cloned and screened against a panel of self‐antigens and microbial recall antigens to interrogate their antigen reactivity. The percentage of CD4+ T cells entering cell cycle in response to self‐peptide/MHC was calculated to be 0.04%, and entry into cell cycle was dependent upon CD28 costimulation. Clones derived from CFSElow T cells exhibited significantly greater cross‐reactivity to multiple antigens than CFSEhigh clones or other CD4+ clones generated after microbial antigen stimulation. Sequencing the TCRβ chains indicated that CFSElow clones were indeed clonal. These data demonstrate that T cell clones generated on stimulation by endogenous self‐peptides exhibit a high degree of multispecificity, and we speculate that their multispecificity is based upon recognition of shared‐backbone MHC determinants.
A New Silver(I) Aggregate Having an Octagonal Ag4S4 Core Where μ3‐S Bonding Interactions Lead to a Nanotube Assembly that Exhibits Quasiaromaticity
Authors: Zartilas Sotiris , Kourkoumelis Nikolaos , Hadjikakou Sotiris K. , Hadjiliadis Nick , Zachariadis Panagiotis , Kubicki Maciej , Denisov Alexey Yu. , Butler Ian S. 
Published: February 2007

AbstractSilver(I) chloride reacts with 2‐mercapto‐3,4,5,6‐tetrahydropyrimidine (StpmH2, C4H8N2S) in DMSO with excess triethylamine to give a complex of formula {[Ag4Cl4(μ3‐StpmH2)4]n} (1). The product was characterized by elemental analyses, FTIR far‐IR, UV/Vis, and 1H and 109Ag NMR spectroscopic techniques. The 109Ag NMR spectroscopic data of the complexes {[Ag6(μ2‐Br)6(μ2‐StpmH2)4(μ3‐StpmH2)2]n} (2) and {[Ag4(μ2‐StpmH2)6](NO3)4}n (3) are also reported here for comparison. Crystal structure of complex 1 was determined by X‐ray diffraction at 100(1) K. Complex 1, C4H8AgClN2S, crystallized in the tetragonal system, space group P4cc, a = 15.7761(9) Å, b = 15.7761(9) Å, c = 6.9624(8) Å, V = 1732.8(2) Å3, Z = 2. Each metal ion is bonded to one terminal Cl atom and three μ3‐S atoms from three StpmH2 ligands. Four silver ions are bridged by four sulfur atoms forming an octagonal Ag4S4 core. Each AgI ion of one core is also bridged to an AgI ion of another core through a sulfur atom, which forms an infinite nanotube structure. A computational study utilizing the method of nucleus‐independent chemical shifts (NICS) showed that the Ag4S4 core exhibits strong quasiaromaticity at the geometric cage center. To the best of our knowledge, this is the first example of an AgI cluster that presents quasiaromaticity and stacking interactions.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Surface modification of poly(methyl methacrylate) microfluidic devices for high‐resolution separations of single‐stranded DNA
Authors: Llopis Shawn L. , Osiri John , Soper Steven A. 
Published: February 2007

AbstractWhile polymer‐based microfluidic devices offer some unique opportunities in developing low‐cost systems for a variety of application areas, the ability to sort electrophoretically with high efficiency a number of different targets has remained somewhat elusive with an example consisting of achieving single base resolution as required for DNA sequencing. While the reasons for this are many‐fold, it is clear that some type of coating is required on the polymer substrate to suppress the EOF and/or minimize potential solute/wall interactions. To this end, we report on a simple grafting procedure to allow the formation of polymer coats, which in this example used linear polyarcylamides (LPAs), onto a poly(methyl methacrylate) (PMMA) microfluidic device. The procedure involved creating an amine‐terminated PMMA surface by appropriately functionalizing the PMMA through either a chemical or photochemical process. The aminated surface could then be used to covalently anchor methacrylic acid, which was used as a scaffold to produce LPAs on the surface through radical polymerization of acrylamide. The resulting surfaces demonstrated EOFs that were nearly an order of magnitude smaller than native PMMA. In addition, these LPA‐coated devices could produce highly reproducible migration times of over ˜20 runs with plate numbers exceeding 105 m−1. Using gel electrophoretic analysis of a single base track generated from an M13mp18 template using Sanger cycle sequencing and dye‐primer chemistry, the resolution value obtained for bases 199 and 200 was 0.18 while for bases 208 and 209 it was 0.21. For the native PMMA, these bands were found to comigrate.
Comparison of chemical composition and antifungal activity of Curcuma longa L. leaf oils produced by different water distillation techniques
Authors: Babu G. D. Kiran , Shanmugam V. , Ravindranath S. D. , Joshi V. P. 
Published: February 2007

AbstractCurcuma longa leaves, an unexploited agricultural waste in the hilly terrains of the western Himalayas in India, were exploited to isolate essential oil. The efficiency of vacuum distillation (150 mmHg) over conventional distillation at atmospheric pressure was assessed on the quantitative and qualitative characteristics of these leaf oils, known for high monoterpene content and possessing lower boiling points. The oil yields were comparatively lower in vacuum distillation (0.25%) than conventional distillation (0.28%). GC and GC–MS analyses revealed that the vacuum‐distilled oil and the conventionally distilled oil contained maximum total monoterpenoids (88.2%) and sesquiterpenoids (45.7%), respectively, followed by ‘residual oil’, produced by redistilling the leaves at atmospheric pressure after vacuum distillation. Further, the ratio of monoterpenoids to sesquiterpenoids in the vacuum‐distilled oil was 10 times higher (10.5) than the conventionally distilled oil (1.0). These variations are attributed to the fact that in vacuum distillation, the constituents with lower boiling points are easily distilled off, leaving behind the higher boiling point constituents, which are otherwise extracted in the conventional distillation. In antifungal assays of these essentail oils against the fungal pathogens Fusarium oxysporum f. sp. dianthi and Alternaria dianthi, infecting carnations, and F. oxysporum f. sp. gladioli and Curvularia trifolii f. sp. gladioli infecting gladioli, the residual oil showed better antifungal activity over other oil samples at each of the tested concentrations. Either the high content of sesquiterpenoids or the combined effect of the composition/ratio of mono‐ and sesquiterpenoids might have enhanced the antifungal activities. These studies clearly established the significance of a waste yielding useful products and the usefulness of the modified water distillation methods for producing essential oils with high‐quality profiles in terms of chemical composition and antifungal activity, except for oil yields. Copyright © 2007 John Wiley & Sons, Ltd.