bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of conjugated carbon bonds on poly(vinyl chloride) films by microwave‐discharge oxygen‐plasma treatments
Authors: Kumagai Hidetoshi , Tashiro Tomokatu , Kobayashi Takaomi
Published: February 2005

Conjugated polyene bonds on poly(vinyl chloride) (PVC) films were rapidly formed by the treatment of oxygen plasma produced by microwave discharge. Changes affecting the formation of conjugated carbon bonds on PVC were studied with respect to plasma emission diagnostic and surface properties of the film with fluorescence, refractant absorption spectroscopy, X‐ray photoelectron spectroscopy analysis, and Raman spectroscopy. The formation of polyene bonds on the film surface was responsible for both the dechlorination and dehydrogenation of PVC in the plasma atmosphere. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 589–594, 2005
Superior Safety in Noninferiority Trials
Authors: Bristol David R.
Published: February 2005

Noninferiority of a new treatment to a reference treatment with respect to efficacy is usually associated with the superiority of the new treatment to the reference treatment with respect to other aspects not associated with efficacy. When the superiority of the new treatment to the reference treatment is with respect to a specified safety variable, it may be necessary to perform the between‐treatment comparisons. The efficacy and safety comparisons may be considered separately or simultaneous comparisons may be performed. Here techniques are discussed for the simultaneous consideration of both aspects. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Biostatistical Assessment of Mutagenicity Studies by Including the Positive Control
Authors: Hauschke Dieter , Slacik‐Erben Renate , Hensen Sabrina , Kaufmann Ronny
Published: February 2005

Statistical analysis plays a fundamental part in the evaluation of mutagenicity experiments. However, a statistically significant or non‐significant test result without incorporating the biological relevance cannot be a valid scientific criterion for concluding a positive or negative effect of the underlying compound (Hauschke et al., 1997). The classification of an experiment as being negative or positive should be based also on the magnitude of the responses in the positive control. We address the problem of determining the maximum safe dose by incorporating a biologically meaningful threshold value, which is expressed as a fraction of the difference between positive and vehicle control. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Methods for Assessing Noninferiority with Censored Data
Authors: Freitag Gudrun
Published: February 2005

In this paper we present the existing approaches to the problem of showing noninferiority with randomly right censored data. The main focus is on the choice of the discrepancy measure which is used to define the deviation from the classical null hypothesis, i.e. the noninferiority margin. Most methods are based on certain parametric or semiparametric assumptions. In contrast, a new, completely nonparametric approach is suggested and discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Regulatory Perspective on Choice of Margin and Statistical Inference Issue in Non‐inferiority Trials
Authors: Hung H. M. James , Wang Sue‐Jane , O'Neill Robert
Published: February 2005

Without a placebo arm, any non‐inferiority inference involving assessment of the placebo effect under the active control trial setting is difficult. The statistical risk for falsely concluding non‐inferiority cannot be evaluated unless the constancy assumption approximately holds that the effect of the active control under the historical trial setting where the control effect can be assessed carries to the non‐inferiority trial setting. The constancy assumption cannot be checked because of missing the placebo arm in the non‐inferiority trial. Depending on how serious the violation of the assumption is thought to be, one may need to seek an alternative design strategy that includes a cushion for a very conservative non‐inferiority analysis or shows superiority of the experimental treatment over the control. Determination of the non‐inferiority margin depends on what objective the non‐inferiority analysis is intended to achieve. The margin can be a fixed margin or a margin functionally defined. Between‐trial differences always exist and need to be properly considered. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Special Invited Papers Section: Therapeutic Equivalence – Clinical Issues and Statistical Methodology in Noninferiority Trials
Authors: Lange S. , Freitag G.
Published: February 2005

An essential problem in planning clinical non‐inferiority or equivalence studies is the specification of the ‘irrelevant difference’ (irrelevance margin; delta). This quantifies the amount of non‐inferiority or difference, respectively, between a new test therapy and an established standard treatment which is to be considered as tolerable. In the past, most recommendations and guidelines for clinical non‐inferiority and equivalence studies contained only general statements and formulations concerning the specification of delta. The current unsatisfactory situation was the reason for performing a systematic review of published clinical non‐inferiority and equivalence studies. It was the aim to gain an overview on the irrelevance margins used in such studies, and on reasons for choosing the particular margins. For the sake of comparability, the irrelevance margins were converted into standardized differences and odds ratios. Overall, there were 332 non‐inferiority or equivalence trials obtained by means of an extensive literature search. The results of the systematic review show that current requirements on the choice of delta and the reality of recent clinical non‐inferiority and equivalence trials differ substantially. In about one half of the trials a difference of 0.5 standard deviations or more was regarded as ‘irrelevant’ – explicitly or implicitly. Estimates of standard‐placebo differences formed the basis of the irrelevance margin in less than every tenth trial. Reasons for this very low proportion might be (1) the possibly resulting very small irrelevance margins, and (2) unsolved problems of the requirements themselves. Overall, it seems that a more global definition of ‘irrelevance’ might be warranted. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Testing Superiority and Non‐Inferiority Hypotheses in Active Controlled Clinical Trials
Authors: Tsong Yi , Zhang Juan (Joanne)
Published: February 2005

Switching between testing for superiority and non‐inferiority has been an important statistical issue in the design and analysis of active controlled clinical trial. In practice, it is often conducted with a two‐stage testing procedure. It has been assumed that there is no type I error rate adjustment required when either switching to test for non‐inferiority once the data fail to support the superiority claim or switching to test for superiority once the null hypothesis of non‐inferiority is rejected with a pre‐specified non‐inferiority margin in a generalized historical control approach. However, when using a cross‐trial comparison approach for non‐inferiority testing, controlling the type I error rate sometimes becomes an issue with the conventional two‐stage procedure. We propose to adopt a single‐stage simultaneous testing concept as proposed by Ng (2003) to test both non‐inferiority and superiority hypotheses simultaneously. The proposed procedure is based on Fieller's confidence interval procedure as proposed by Hauschke et al. (1999). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Statistical Methods for the Analysis of Two‐Arm Non‐inferiority Trials with Binary Outcomes
Authors: Wellek Stefan
Published: February 2005

The aim of this contribution is to give an overview of approaches to testing for non‐inferiority of one out of two binomial distributions as compared to the other in settings involving independent samples (the paired samples case is not considered here but the major conclusions and recommendations can be shown to hold for both sampling schemes). In principle, there is an infinite number of different ways of defining (one‐sided) equivalence in any multiparameter setting. In the binomial two‐sample problem, the following three choices of a measure of dissimilarity between the underlying distributions are of major importance for real applications: the odds ratio (OR), the relative risk (RR), and the difference (DEL) of both binomial parameters. It is shown that for all three possibilities of formulating the hypotheses of a non‐inferiority problem concerning two binomial proportions, reasonable testing procedures providing exact control over the type‐I error risk are available. As a particularly useful and versatile way of handling mathematically nonnatural parametrizations like RR and DELTA, the approach through Bayesian posterior probabilities of hypotheses with respect to some non‐informative reference prior has much to recommend it. In order to ensure that the corresponding testing procedure be valid in the classical, i.e. frequentist sense, it suffices to use straightforward computational techniques yielding suitably corrected nominal significance levels.

In view of the availability of testing procedures with satisfactory properties for all parametrizations of main practical interest, the discussion of the pros and cons of these methods has to focus on the question of which of the underlying measures of dissimilarity should be preferred on grounds of logic and intuition. It is argued that the OR clearly merits to be given preference also with regard to this latter kind of criteria since the non‐inferiority hypotheses defined in terms of the other parametric functions are bounded by lines which cross the boundaries of the parameter space. From this fact, we conclude that the exact Fisher type test for one‐sided equivalence provides the most reasonable approach to the confirmatory analysis of non‐inferiority trials involving two independent samples of binary data. The marked conservatism of the nonrandomized version of this test can largely be removed by using a suitably increased nominal significance level (depending, in addition to the target level, on the sample sizes and the equivalence margin), or by replacing it with a Bayesian test for non‐inferiority with respect to the odds ratio. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Therapeutic Equivalence – Clinical Issues and Statistical Methodology in Noninferiority Trials
Authors: Munk Axel , Trampisch Hans J.
Published: February 2005

This special issue on therapeutic equivalence contains a selection of 8 papers presented at the conference ‘Therapeutic Equivalence – Clinical Issues and Statistical Methodology in Noninferiority Trials’ held in Düsseldorf, December 12–13, 2003. The aim of this conference was to gather experts from academics, industry and regulatory agencies in the field of therapeutic equivalence, in particular of noninferiority trials. Originally initiated as a small workshop, it soon turned out that there is obviously strong need to discuss these challenging issues at a broader auditorium. Indeed, the feedback to this conference was overwhelming, finally more than 300 researchers participated. Hence the idea emerged to collect the results and discussions in a single journal issue. It took more than a year to finish it, and various activities in this rapidly developing area have been going on and were incorporated.

We are very grateful to the Editors E. Brunner and M. Schumacher of the Biometrical Journal for their encouragement and support to publish this special issue on the occasion of this conference. Further, the technical assistance and expertise of G. Skipka and K. Thangavelu is gratefully acknowledged. We are also indebted to Peter Bauer and Stephen Senn for their discussions of the subsequent articles by Bristol, Freitag, Hauschke, Slacik‐Erben, Hensen and Kaufmann, Hung, Wang and O'Neill, Lange and Freitag, Tsong and Zhang, Wellek, and last but not least we would like to thank Joachim Röhmel for his contribution to this special issue. Joachim Röhmel contributed significantly during the last three decades to various branches of biostatistical research, and in particular to the design and analysis of equivalence trials. The aim of this special issue is therefore twofold, it is also devoted to the occasion of Joachim Röhmel's retirement from BfArM in 2004. In the following we would briefly like to express our deep appreciation of his scientific work. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Statistical optimization of culture conditions for bacterial cellulose production using Box‐Behnken design
Authors: Bae Sangok , Shoda Makoto
Published: February 2005

Culture conditions in a jar fermentor for bacterial cellulose (BC) production from A. xylinum BPR2001 were optimized by statistical analysis using Box‐Behnken design. Response surface methodology was used to predict the levels of the factors, fructose (X1), corn steep liquor (CSL) (X2), dissolved oxygen (DO) (X3), and agar concentration (X4). Total 27 experimental runs by combination of each factor were carried out in a 10‐L jar fermentor, and a three‐dimensional response surface was generated to determine the effect of the factors and to find out the optimum concentration of each factor for maximum BC production and BC yield. The fructose and agar concentration highly influenced the BC production and BC yield. However, the optimum conditions according to changes in CSL and DO concentrations were predicted at almost central values of tested ranges. The predicted results showed that BC production was 14.3 g/L under the condition of 4.99% fructose, 2.85% CSL, 28.33% DO, and 0.38% agar concentration. On the other hand, BC yield was predicted in 0.34 g/g under the condition of 3.63% fructose, 2.90% CSL, 31.14% DO, and 0.42% agar concentration. Under optimized culture conditions, improvement of BC production and BC yield were experimentally confirmed, which increased 76% and 57%, respectively, compared to BC production and BC yield before optimizing the culture conditions. © 2005 Wiley Periodicals, Inc.
Engineered Saccharomyces cerevisiae strain BioS‐1, for the detection of water‐borne toxic metal contaminants
Authors: Radhika V. , Milkevitch Matthew , Audigé Valéry , Proikas‐Cezanne Tassula , Dhanasekaran N.
Published: February 2005

Saccharomyces cerevisiae responds to extracellular toxic stimuli by increasing intracellular cyclic AMP levels, leading to activation of a cAMP‐dependent protein kinase, protein kinase A (PKA). Activated PKA phosphorylates downstream substrates, including specific DNA‐binding proteins, to turn off the expression of most or all of the yeast genes. Such cAMP‐PKA‐mediated inhibition of gene expression in response to toxic stimuli appears to be unique to S. cerevisiae. For instance, in mammalian cells, the cAMP‐PKA signaling pathway is rather responsive to growth factors and hormones in addition to being primarily involved in the activation of gene expression. Activation of gene expression by the cAMP‐PKA pathway in mammalian cells is due mainly to the presence of cAMP‐response elements (CREs) located in the promoters of many mammalian genes, and the expression of PKA‐responsive stimulatory transcription factor CRE‐binding protein, commonly referred as CREBP, which binds to the CREs. Thus, activation of the cAMP‐PKA signaling pathway results in the phosphorylation of CREBP by PKA, and phosphorylated CREBP transactivates specific gene expression by interacting with the cognate CRE. Based on these findings, we sought to engineer a yeast‐based biosensor, in which the stress‐sensing cAMP‐PKA pathway of yeast is coupled to the mammalian CREBP‐CRE‐stimulated gene expression pathway, which drives the expression of a reporter protein, such as green fluorescent protein (GFP). As a primary step toward the development of this biosensor, we engineered a yeast strain, BioS‐1, by genetically altering YPH 501, a wild‐type strain of S. cerevisiae, to express human CREBP and human CRE promoter‐driven GFP. Exposure of BioS‐1 to varying concentrations of As3+, Fe2+, Pb2+, and Cd2+ elicits concentration‐dependent expression of the GFP reporter that can be easily monitored by the fluorescence emitted by GFP. The results also indicate that the engineered BioS‐1 yeast cells can detect 2.5 ppm of these toxic metals and report it through the expression of GFP within 3 h. The results presented herein demonstrate that this engineered yeast strain can detect metal toxicants and can validate the use of this prototypic yeast strain to develop a biosensor that can be used to detect and monitor cytotoxic water‐borne toxic heavy metals. © 2005 Wiley Periodicals, Inc.
Crystal Structures, Anisotropic Growth, and Optical Properties: Controlled Synthesis of Lanthanide Orthophosphate One‐Dimensional Nanomaterials
Authors: Yan Ruoxue , Sun Xiaoming , Wang Xun , Peng Qing , Li Yadong
Published: February 2005

The fundamental understanding of the relationship between crystal structure and the dynamic processes of anisotropic growth on the nanoscale, and exploration of the key factors governing the evolution of physical properties in functional nanomaterials, have become two of the most urgent and challenging issues in the fabrication and exploitation of functional nanomaterials with designed properties and the development of nanoscale devices. Herein, we show how structural and kinetic factors govern the tendency for anisotropic growth of such materials under hydrothermal conditions, and how the crystal structure and morphology influence the optical properties of Ln3+‐doped nanocrystals. The synthesis of phase‐pure and single‐crystalline monoclinic, hexagonal, and tetragonal one‐dimensional LnPO4 nanostructures of different aspect ratios by means of kinetically controlled hydrothermal growth processes is demonstrated. It is shown that the tendency for anisotropic growth under hydrothermal conditions can be enhanced simply by modifying the chemical potentials of species in the reaction solution through the use of carefully selected chelating ligands. A systematic study of the photoluminescence of various Eu3+‐doped lanthanide phosphates has revealed that the optical properties of these nanophosphors are strongly dependent on their crystal structures and morphologies.
Pseudorotation Barriers of Biological Oxyphosphoranes: A Challenge for Simulations of Ribozyme Catalysis
Authors: López Carlos Silva , Faza Olalla Nieto , de Lera Angel R. , York Darrin M.
Published: February 2005

Pseudorotation reactions of biologically relevant oxyphosphoranes were studied by using density functional and continuum solvation methods. A series of 16 pseudorotation reactions involving acyclic and cyclic oxyphosphoranes in neutral and monoanionic (singly deprotonated) forms were studied, in addition to pseudorotation of PF5. The effect of solvent was treated by using three different solvation models for comparison. The barriers to pseudorotation ranged from 1.5 to 8.1 kcal mol−1 and were influenced systematically by charge state, apicophilicity of ligands, intramolecular hydrogen bonding, cyclic structure and solvation. Barriers to pseudorotation for monoanionic phosphoranes occur with the anionic oxo ligand as the pivotal atom, and are generally lower than for neutral phosphoranes. The OCH3 groups were observed to be more apicophilic than OH groups, and hence pseudorotations that involve axial OCH3/equatorial OH exchange had higher reaction and activation free energy values. Solvent generally lowered barriers relative to the gas‐phase reactions. These results, together with isotope 18O exchange experiments, support the assertion that dianionic phosphoranes are not sufficiently long‐lived to undergo pseudorotation. Comparison of the density functional results with those from several semiempirical quantum models highlight a challenge for new‐generation hybrid quantum mechanical/molecular mechanical potentials for non‐enzymatic and enzymatic phosphoryl transfer reactions: the reliable modeling of pseudorotation processes.
Benzoyl Transfer Reactivities of Racemic 2,4‐Di‐O‐acyl‐myo‐inosityl 1,3,5‐Orthoesters in the Solid State: Molecular Packing and Intermolecular Interactions Correlate with the Ease of the Reaction
Authors: Sarmah Manash P. , Gonnade Rajesh G. , Shashidhar Mysore S. , Bhadbhade Mohan M.
Published: February 2005

Racemic 2,4‐di‐O‐acyl‐myo‐inosityl 1,3,5‐orthoesters undergo transesterification catalyzed by sodium carbonate with varying ease of reaction in the solid state; reactions in solution and melt do not show such varied differences. An interesting crystal of a 1:1 molecular complex of highly reactive racemic 2,4‐di‐O‐benzoyl‐myo‐inosityl 1,3,5‐orthoformate and its orthoacetate analogue exhibited better reactivity than the latter component alone. Single‐crystal X‐ray structures of the reactants have been correlated with the observed differences in the acyl‐transfer efficiencies in the solid state. Although each of the derivatives helically self‐assembles around the crystallographic 21 axis linked through OH⋅⋅⋅O hydrogen bonding, the pre‐organization of the reactive groups (CO [El] and OH [Nu]), CH⋅⋅⋅O and the CH⋅⋅⋅π interactions are significantly more favourable for the reactive derivatives than the less reactive ones. Bond‐length distributions also showed differences; the OC bond of the axial benzoyl group, which gets cleaved during the reaction, is longer (1.345–1.361 Å) relative to the chemically equivalent OC bond of the equatorial benzoyl group (1.316–1.344 Å) in the reactive derivatives. These bond‐length differences are not significant in the less reactive derivatives. The overall molecular organization is different too; the strikingly discrete helices, which may be viewed as “reaction tunnels” and are held by interhelical interactions, are clearly evident in the reactive derivatives in comparison with the less reactive ones.
Nonenzymatic Glucose Detection by Using a Three‐Dimensionally Ordered, Macroporous Platinum Template
Authors: Song Yan‐Yan , Zhang Dai , Gao Wei , Xia Xing‐Hua
Published: February 2005

A three‐dimensionally ordered, macroporous, inverse‐opal platinum film was synthesized electrochemically by the inverted colloidal‐crystal template technique. The inverse‐opal film that contains platinum nanoparticles showed improved electrocatalytic activity toward glucose oxidation with respect to the directly deposited platinum; this improvement is due to the interconnected porous structure and the greatly enhanced effective surface area. In addition, the inverse‐opal Pt‐film electrode responds more sensitively to glucose than to common interfering species of ascorbic acid, uric acid, and p‐acetamidophenol due to their different electrochemical reaction mechanisms. Results showed that the ordered macroporous materials with enhanced selectivity and sensitivity are promising for fabrication of nonenzymatic glucose biosensors.
Acidity Trends in α,β‐Unsaturated Sulfur, Selenium, and Tellurium Derivatives: Comparison with C‐, Si‐, Ge‐, Sn‐, N‐, P‐, As‐, and Sb‐Containing Analogues
Authors: Guillemin Jean‐Claude , Riague El Hassan , Gal Jean‐François , Maria Pierre‐Charles , Mó Otilia , Yáñez Manuel
Published: February 2005

The gas‐phase acidity of CH3CH2XH (X=S, Se, Te), CH2CHXH (X=S, Se, Te) and PhXH (X=S, Se) compounds was measured by means of Fourier transform ion cyclotron resonance mass spectrometry. To analyze the role that unsaturation plays on the intrinsic acidity of these systems, a parallel theoretical study, in the framework of the G2 and the G2(MP2) theories, was carried out for all ethyl, ethenyl (vinyl), ethynyl, and phenyl O‐, S‐, Se‐, and Te‐containing derivatives. Unsaturated compounds are stronger acids than their saturated analogues, because of the strong π‐electron donor ability of the heteroatoms that contributes to a large stabilization of the unsaturated anions. Ethynyl derivatives are stronger acids than vinyl compounds, while phenyl derivatives have an intrinsic acidity intermediate between that of the corresponding vinyl and ethynyl analogues. The CH2CHXH vinyl compounds (enol‐like) behave systematically as slightly stronger acids than their CH3C(H)X (keto‐like) tautomers. Vinyl derivatives are stronger acids than ethyl compounds, because the anion stabilization attributable to unsaturation is greater than that undergone in the neutral compounds. Conversely, the enhanced acidity of the ethynyl derivatives with respect to the vinyl compounds is due to two concomitant effects, the stabilization of the anion and the destabilization of the neutral compound. The acidities of ethyl, vinyl, and ethynyl derivatives containing heteroatoms of Groups 14, 15, and 16 of the periodic table are closely related, and reflect the differences in electronegativity of the CH3CH2, CH2CH, and CHC groups.
Titanium Imido Complexes of Cyclooctatetraenyl Ligands
Authors: Dunn Simon C. , Hazari Nilay , Jones Nicholas M. , Moody Aidan G. , Blake Alexander J. , Cowley Andrew R. , Green Jennifer C. , Mountford Philip
Published: February 2005

Reaction of [Ti(NR)Cl2(py)3] (R=tBu or 2,6‐iPr2C6H3) with K2[COT] (COT=C8H8) or Li2[COT′′] (COT′′=1,4‐C8H6(SiMe3)2) gave the monomeric complexes [Ti(NR)(η8‐COT)] or [Ti(NR)(η8‐COT′′)], respectively. The pseudo‐two coordinate, ′pogo stick′ geometry for these complexes is unique in both early transition‐metal and cyclooctatetraenyl ligand chemistry. In contrast, reaction of [Ti(N‐2,6‐Me2C6H3)Cl2(py)3] with K2[COT] gave the μ‐imido‐bridged dimer [Ti2(μ‐N‐2,6‐Me2C6H3)2(η8‐COT)2]. It appears that as the steric bulk of the imido and C8 ring substituents are decreased, dimerisation becomes more favourable. Aryl imido COT complexes were also prepared by imido ligand exchange reactions between anilines and [Ti(NtBu)(η8‐COT)] or [Ti(NtBu)(η8‐COT′′)]. The complexes [Ti(NtBu)(η8‐COT)], [Ti(N‐2,6‐iPr2C6H3)2(η8‐COT)] and [Ti2(μ‐N‐2,6‐Me2C6H3)2(η8‐COT)2] have been crystallographically characterised. The electronic structures of both the monomeric and dimeric complexes have been investigated by using density functional theory (DFT) calculations and gas‐phase photoelectron spectroscopy. The most striking aspect of the bonding is that binding to the imido nitrogen atom is primarily through σ and π interactions, whereas that to the COT or COT′′ ring is almost exclusively through δ symmetry orbitals. A DFT‐based comparison between the bonding in [Ti(NtBu)(η8‐COT)] and the bonding in the previously reported late transition‐metal ′pogo‐stick′ complexes [Os(NtBu)(η6‐C6Me6)], [Ir(NtBu)(η5‐C5Me5)] and [Ni(NO)(η5‐C5H5)] has also been undertaken.
One‐Dimensional Polymers Based on [{CpMo(CO)2}2(μ,η2‐P2)]: Solid‐State Conformation Analysis by NMR Spectroscopy and DFT Calculations
Authors: Scheer Manfred , Gregoriades Laurence , Bai Junfeng , Sierka Marek , Brunklaus Gunther , Eckert Hellmut
Published: February 2005

Reaction of the complex [{CpMo(CO)2}2(μ,η2‐P2)] (1) with CuI halides leads to the quantitative formation of the novel one‐dimensional linear polymers [CuX{Cp2Mo2(CO)4(μ,η2:η1:η1‐P2)}]∞ (X=Cl (4), Br (5), I (6)). The same products 4 and 5 were obtained when 1 was treated with CuCl2 and CuBr2, respectively. The solid‐state structures are compared and their remarkable influence on the respective 31P magic angle spinning (MAS) NMR spectra is interpreted with the help of density functional theory (DFT) calculations on the model compounds [{(CuX)2{Cp2Cr2(CO)4(μ,η2:η1:η1‐P2)}2}3] (X=Cl (4 a), Br (5 a)) in which the molybdenum atoms are replaced by their lighter homologue chromium.
Pentafluorophenyl–Phenyl Interactions in Biphenyl‐DNA
Authors: Zahn Alain , Brotschi Christine , Leumann Christian J.
Published: February 2005

We prepared and investigated oligonucleotide duplexes of the sequence d(GATGAC(X)nGCTAG)⋅d(CTAGC(Y)nGTCATC), in which X and Y designate biphenyl‐ (bph) and pentafluorobiphenyl‐ (5Fbph) C‐nucleotides, respectively, and n varies from 0–4. These hydrophobic base substitutes are expected to adopt a zipperlike, interstrand stacking motif, in which not only bph/bph or 5Fbph/5Fbph homo pairs, but also 5Fbph/bph mixed pairs can be formed. By performing UV‐melting curve analysis we found that incorporation of a single 5Fbph/5Fbph pair leads to a duplex that is essentially as stable as the unmodified duplex (n=0), and 2.4 K more stable than the duplex with the nonfluorinated bph/bph pair. The Tm of the mixed bph/5Fbph pair was in between the Tm values of the respective homo pairs. Additional, unnatural aromatic pairs increased the Tm by +3.0–4.4 K/couple, irrespective of the nature of the aromatic residue. A thermodynamic analysis using isothermal titration calorimetry (ITC) of a series of duplexes with n=3 revealed lower (less negative) duplex formation enthalpies (ΔH) in the 5Fbph/5Fbph case than in the bph/bph case, and confirmed the higher thermodynamic stability (ΔG) of the fluorinated duplex, suggesting it to be of entropic origin. Our data are compatible with a model in which the stacking of 5Fbph versus bph is dominated by dehydration of the aromatic units upon duplex formation. They do not support a model in which van der Waals dispersive forces (induced dipoles) or electrostatic (quadrupole) interactions play a dominant role.
Betaine‐Induced Assembly of Neutral Infinite Columns and Chains of Linked Silver(I) Polyhedra with Embedded Acetylenediide
Authors: Zhao Xiao‐Li , Wang Quan‐Ming , Mak Thomas C. W.
Published: February 2005

Ten polymeric silver(I) double salts containing embedded acetylenediide: [(Ag2C2)2(AgCF3CO2)9(L1)3] (1), [(Ag2C2)2(AgCF3CO2)10(L2)3]⋅H2O (2), [(Ag2C2)(AgCF3CO2)4(L3)(H2O)]⋅0.75 H2O (3), [(Ag2C2)1.5(AgCF3CO2)7(L4)2] (4), [(Ag2C2)(AgCF3CO2)7(L5)2(H2O)] (5), [(Ag2C2) (AgC2F5CO2)7(L1)3(H2O)] (6), [(Ag2C2)(AgCF3CO2)7(L1)3(H2O)]⋅2 H2O (7), [(Ag2C2)(AgC2F5CO2)6(L3)2] (8), [(Ag2C2)2(AgC2F5CO2)12(L4)2(H2O)4]⋅H2O (9), and [(Ag2C2)(AgCF3CO2)6(L3)2(H2O)]⋅H2O (10) have been isolated by varying the types of betaines, the perfluorocarboxylate ligands employed, and the reaction conditions. Single‐crystal X‐ray analysis has shown that 1–4 all have a columnar structure composed of fused silver(I) double cages, with C22− species embedded in its stem and an exterior coat comprising anionic and zwitterionic carboxylates. For 5 and 6, single silver(I) cages are linked into a beaded chain through both types of carboxylate ligands. In 7, two different coordination modes of L1 connect the silver(I) polyhedra into a chain. For 8, the μ2‐O,O′ coordination mode of L3 connects the silver(I) double cages into a chain. Compound 9 exhibits a two‐dimensional architecture generated from the cross‐linkage of double cages by C2F5CO2−, L4, and [Ag2(C2F5CO2)2] units. Similar to 9, 10 is also a two‐dimensional structure, which is formed by connecting the chains of linked double cages through [Ag2(CF3CO2)2] bridging.
Cullin‐5 plays multiple roles in cell fate specification and synapse formation during Drosophila development
Authors: Ayyub Champakali , Sen Anindya , Gonsalves Foster , Badrinath Kishan , Bhandari Poonam , Shashidhara L.S. , Krishna Sudhir , Rodrigues Veronica
Published: February 2005

We describe a developmental analysis of Drosophila Cullin‐5 (Cul‐5) identified from the genome sequence on the basis of its high degree of homology to vertebrate and worm sequences. The gene is expressed in a restricted manner in ectodermal cells throughout development suggesting pleiotropic functions. We decided to examine the phenotypes of Cul‐5 aberrations in two well‐studied developmental systems: the neuromuscular junction (NMJ) and the developing sensory organ. Alteration of Cul‐5 levels in motoneurons results in an increase in bouton number at the NMJ. The cells of a sensory organ on the adult notum arise from a single progenitor cell by regulated cell division. Aberrations in Cul‐5 affect different steps in the lineage consistent with a role in cell fate determination, proliferation, and death. Such phenotypes highlight the multiple cellular processes in which Cul‐5 can participate. Developmental Dynamics 232:865–875, 2005. © 2005 Wiley‐Liss, Inc.
Killer cell immunoglobulin‐like receptors (KIR) of the African‐origin sabaeus monkey: evidence for recombination events in the evolution of KIR
Authors: Hershberger Karen L. , Kurian Jessica , Korber Bette T. , Letvin Norman L.
Published: February 2005

Killer cell immunoglobulin (Ig)‐like receptors (KIR) were characterized in the West African sabaeus monkey (Chlorocebus sabaeus) to elucidate the mechanism by which diversity evolves in this family of molecules. Complementary DNA encoding four forms of KIR molecules, including KIR3DL, KIR2DL4, KIR2DL5, and KIR3DH forms, were identified in two unrelated sabaeus monkeys. A novel hybrid form showing features found in both KIR2DL5 and KIR3DH was also identified. Both the KIR3DL and KIR3DH forms from the sabaeus monkey were considerably more polymorphic than any KIR form identified in great apes or humans. The polymorphic residues of the three Ig‐like domains were frequently located in structural loops, indicating that point mutations have occurred in these regions. The three Ig‐like domains of the KIR3D forms of six primate species were found to have different patterns of clustering in phylogenetic trees, suggesting that each Ig‐like domain has a distinct phylogenetic history. This variation in relationships suggests that repeated recombination events have occurred between the Ig‐like domains during the evolution of the KIR family in primates. Recombination between individual Ig‐like domains, in addition to point mutations, provides a mechanism for generating the diversity of the KIR genes.
Contribution of stromal cells to the migration, function and retention of plasma cells in human spleen: potential roles of CXCL12, IL‐6 and CD54
Authors: Ellyard Julia I. , Avery Danielle T. , Mackay Charles R. , Tangye Stuart G.
Published: February 2005

Plasma cells (PC) localize to discrete areas of secondary lymphoid tissue and bone marrow (BM). The positioning of PC in different sites is believed to be regulated by chemokines and adhesion molecules expressed by accessory cells in the lymphoid tissue microenvironment. However, the mechanisms responsible for the positioning of PC within the red pulp (RP) of human spleen have not been elucidated. Therefore, we examined the contribution of human splenic stromal cells to the migration and function of human PC. Splenic PC expressed the chemokine receptor CXCR4 and responded to its ligand CXCL12. In contrast, PC lacked CXCR5 and CCR7, and consequently exhibited minimal migration towards CXCL13 and CCL21. Splenic stromal cells proved to be a rich source of CXCL12, and could induce the migration of human B cells. Furthermore, they supported Ig production by splenic PC mainly by secreting IL‐6. Lastly, a striking difference between splenic and BM PC was the constitutive expression of CD11a by only splenic PC. Notably, splenic stromal cells expressed high levels of CD54, the counter‐structure of CD11a, and splenic PC were positioned adjacent to stromal cells in the RP. Thus, we propose that stromal cells attract PC to the RP and contribute to their retention and function through the combined expression of CXCL12, CD54 and IL‐6.
Peptide immunization excludes antigen‐specific T cells from splenic lymphoid compartments
Authors: Zhang Lei , Lizzio Elaine F. , Chen Trina , Kozlowski Steven
Published: February 2005

Using adoptive transfer of TCR‐transgenic T cells, we examined the homing of transgenic T cells to splenic compartments in situ. After systemic immunization with peptide or protein antigen, the location of clonotypic T cells, cytokine production, cell surface markers, and apoptosis were assessed. There were distinct differences in the splenic homing of CD4+ TCR‐transgenic T cells in mice immunized with peptide as compared to mice immunized with whole‐protein antigen. T cells in peptide‐immunized mice were found almost exclusively in the splenic red pulp, but not in the T and B cell zones (white pulp), while the majority of T cells immunized with whole protein were found in the white pulp. Many more Fas ligand‐expressing and apoptotic cells were present after peptide immunization than after whole‐protein immunization. Localization of IL‐4‐, IL‐2‐ and IFN‐γ‐producing cells to the lymphocyte‐containing splenic white pulp was only observed with whole‐protein immunization. The unique homing and increased apoptosis of immune cells post peptide immunization may help explain the ineffectiveness of many peptide vaccines. Linkage of the same peptide epitope to a carrier protein increased white pulp T cell localization and decreased apoptosis, suggesting a strategy to enhance peptide vaccine responses.
The role of TCR stimulation and TGF‐β in controlling the expression of CD94/NKG2A receptors on CD8 T cells
Authors: Gunturi Anasuya , Berg Rance E. , Crossley Emily , Murray Sean , Forman James
Published: February 2005

Following antigen recognition, murine CD8 T cells express CD94/NKG2A receptors. Our results show that this up‐regulation occurs rapidly in vitro and is accompanied by an ∼8‐fold increase in CD94 and ∼125‐fold increase in NKG2A mRNA. In contrast, only a twofold increase in NKG2C mRNA is noted. The addition of TGF‐β, but not IL‐10, IL‐12 or IL‐15, leads to a further increase in cell membrane expression of these receptors, as well as a ∼6‐fold increase in mRNA for both chains. TGF‐β also increases CD94/NKG2A expression on memory CD8 T cells that are re‐exposed to antigen. The effect of TGF‐β on increasing CD94/NKG2A expression on both naive and memory CD8 T cells occurs only when there is a concurrent stimulation through the TCR. In contrast, TGF‐β does not increase expression of CD94/NKG2A on resting or activated NK cells. We also show by using purified CD8 T cells, that TGF‐β acts directly on these cells. These results implicate a role for both antigen and TGF‐β in increasing expression of inhibitory CD94/NKG2A receptors on CD8 T cells.
MyD88 and TLR2, but not TLR4, are required for host defense against Cryptococcus neoformans
Authors: Biondo Carmelo , Midiri Angelina , Messina Luciano , Tomasello Francesco , Garufi Gabriella , Catania Maria Rosaria , Bombaci Mauro , Beninati Concetta , Teti Giuseppe , Mancuso Giuseppe
Published: February 2005

We investigated here the potential role of Toll‐like receptors (TLR) and the adaptor protein MyD88 in innate immunity responses to Cryptococcus neoformans, a pathogenic encapsulated yeast. Peritoneal macrophages from MyD88–/– or TLR2–/– mice released significantly less TNF‐α, compared with wild‐type controls, after in vitro stimulation with whole yeasts. In contrast, no differences in TNF‐α release were noted between macrophages from C3H/HeJ mice, which have a loss of function mutation in TLR4, relative to C3H/HeN controls. When MyD88‐ or TLR2‐deficient mice were infected with low doses of the H99 serotype A strain, all of the control animals, but none of MyD88–/– and only 38% of the TLR2–/– animals survived, in association with higher fungal burden in the mutant mice. Both MyD88–/– and TLR2–/– animals showed decreased TNF‐α, IL‐12p40 and/or IFN‐γ expression in various organs during infection. No difference in susceptibility to experimental cryptococcosis was found between C3H/HeJ mice and C3H/HeN controls. In conclusion, our data indicate that TLR2 and MyD88, but not TLR4, critically contribute to anti‐cryptococcal defenses through the induction of increased TNF‐α, IL‐12 and IFN‐γ expression.
Mesoporous Materials Promoting Direct Electrochemistry and Electrocatalysis of Horseradish Peroxidase
Authors: Dai Zhihui , Ju Huangxian , Chen Hongyuan
Published: February 2005

The direct electron transfer and electrocatalysis of horseradish peroxidase (HRP) immobilized on hexagonal mesoporous silicas (HMS) matrix was studied. The interaction between HRP and HMS was examined by using Fourier transform infrared spectroscopy, nitrogen adsorption isotherms and electrochemical methods. The immobilized HRP at a modified glassy carbon electrode showed a good direct electrochemical behavior, which depended on the specific properties of the HMS. Two couples of redox peaks corresponding to Fe(III) to Fe(II) conversion of the HRP intercalated in the mesopores and adsorbed on the external surface of the HMS were observed with the formal potentials of −0.315 and −0.161 V in 0.1 M pH 7.0 PBS, respectively. The amount of HRP intercalated in the mesopores of HMS proved to be related to the pore size. The HRP intercalated in the mesopores showed a surface controlled electrode process with a single proton transfer. The immobilized HRP displayed an excellent electrocatalytic response to the reduction of hydrogen peroxide (H2O2) without the aid of an electron mediator. The HMS provided a novel matrix for protein immobilization and direct electron transfer study of the immobilized protein.
Separation and determination of L‐tryptophan and its metabolites by capillary micellar electrokinetic chromatography with amperometric detection
Authors: Wang Wei , Qiu Bin , Xu Xueqin , Zhang Lan , Chen Guonan
Published: February 2005

A high‐performance method of capillary micellar electrokinetic chromatography (CMEKC) with amperometric detection (AD), using a newly designed pre‐aligned electrochemical cell, has been developed for the separation and determination of L‐tryptophan (Trp) and its eight metabolites including 3‐hydroxy‐L‐kynurenine (3‐HK), 5‐hydroxy‐L‐tryptophan (5‐HTP), L‐kynurenine (KN), 5‐hydroxyindole‐3‐acetic acid (5‐HIAA), xanthurenic acid (XA), indole‐3‐pyruvic acid (IPA), 5‐hydroxytryptamine (5‐HT), and tryptamine (Tryp). A carbon disk electrode was used as the working electrode and the optimal detection potential was 0.85 V (versus Ag/AgCl). At 24 kV of applied voltage, the nine compounds were completely separated, within 23 min, in a 10 mol/L Na2HPO4‐NaOH buffer (pH 11.0) containing 40 mmol/L sodium dodecyl sulfate (SDS) and 3% methanol (v/v). A good linear relationship was obtained for all analytes in this paper and the detection limits of 3‐HK, 5‐HTP, KN, Trp, 5‐HIAA, XA, IPA, 5‐HT, and Tryp were 7.42, 5.18, 34.6, 3.99, 15.1, 12.7, 260, 6.72, and 8.01 nmol/L, respectively. This method has been applied to analyze the metabolism of Trp in rabbit urine.
Chiral separation based on ligand‐exchange capillary electrophoresis using a copper(II)‐L‐ornithine ternary complex as selector
Authors: Zheng Zhi‐Xia , Wei Yanlin , Lin Jin‐Ming
Published: February 2005

A ligand‐exchange capillary electrophoresis was explored, with L‐ornithine as the ligand and copper(II) as the central ion. Its applicability was demonstrated with underivatized and dansyl amino acids, a dipeptide, and drugs with amino alcohol structure. The enantioselectivity was found to be strongly dependent on pH and copper(II)‐L‐Orn complex concentration. Due to the adsorption of the positively charged species onto the capillary inner walls, the chiral separation selectivity is very high while the efficiency is relatively low. Permanent 1,3‐propanediamine‐coated capillaries show an improved separation efficiency and theoretical plate numbers increasing from 104 to 105. Similar phenomena were observed when sodium dodecyl sulfate (SDS) micelles were added to the copper(II) complex solution. The poor separation efficiency of chiral compounds in uncoated capillaries may result from the low rate of the ligand‐exchange reactions, and the high enantioselectivity may derive from the complexing process in the adsorbed phase.
Micellar proportion: A parameter to compare the hydrophobicity of the pseudostationary phases or that of the analytes in micellar electrokinetic chromatography
Authors: Dobos Zsófia , Kiss Éva , Hallgas Balázs , Kéri György , Idei Miklós
Published: February 2005

Micellar proportion, tprop,mic = tmic/tm, a quantity expressing how much time is spent by the analyte in the micellar phase related to its whole migration time (tm) has been introduced by utilizing the micellar phase residence time (tmic). The tprop,mic values have been determined for analytes of different chemical structures (alkyl benzene and alkyl phenone homologous series, alcohols, strongly hydrophobic peptides) studied by micellar elektrokinetic chromatography (MEKC) using various cationic and anionic pseudostationary phases. A good linear correlation was obtained between tprop,mic and the calculated hydrophobicity (CLOGP) of the analytes for all pseudostationary phases (CLOGP = A·logtprop,mic + B). Considering a given pseudostationary phase, tprop,mic as a relative quantity is a suitable parameter to characterize and compare experimentally the behavior of the various analytes in MEKC. Applying a set of probe molecules with known hydrophobicity, the CLOGP50 value (showing the value of hydrophobicity of a virtual molecule spending exactly 50% of its migration time in the pseudostationary phase) has been calculated for each pseudostationary phase applied here. This experimentally determinable numerical value (characterizing the pseudostationary phase) can be utilized to compare the hydrophobicity and hence retention ability of the pseudostationary phases. The tprop,mic value was found to be applicable to compare the methylene selectivity of the different pseudostationary phases as well: logtprop,mic = A·Z + B, where Z is the number of carbon atoms of the alkyl chain in the alkyl benzene homologous series.
Analysis of anticancer platinum(II)‐complexes by microemulsion electrokinetic chromatography: Separation of diastereomers and estimation of octanol‐water partition coefficients
Authors: Rappel Christina , Galanski Mathea Sophia , Yasemi Afshin , Habala Ladislav , Keppler Bernhard K.
Published: February 2005

Microemulsion electrokinetic chromatography (MEEKC) was applied for the separation and lipophilicity estimation of oxaliplatin and eight novel anticancer oxaliplatin derivatives. Solubility and permeability have to be balanced in modern drug development, and the octanol‐water partition coefficient (log P) still represents one of the most useful quantifiable parameters providing a reasonable estimation of a drug's lipophilicity. Therefore, the capacity factors from MEEKC were correlated to log P values derived by the traditional shake flask method. The MEEKC method was accomplished using a microemulsion of heptane/sodium dodecyl sulfate (SDS)/butanol in phosphate buffer at pH 7.4 and 37°C with all analytes being in a neutral state during the run. This experimental setup allowed a baseline separation of all platinum complexes within 11 min. Remarkably, beside the very good resolution and precision of the measurements, separation of diastereomers of the complexes and quantification of the diastereomeric ratios could be achieved. Correlating the capacity factors with the corresponding log P values resulted in a linear dependency with a correlation factor of r = 0.9935. Consequently, the applied MEEKC method was found to be a highly valuable technique not only for the separation of platinum complexes but as well for the estimation of the octanol‐water partition coefficient with many advantages in comparison to other methods.