bluuebunny/crossref_metadata_2025_split huggingface dataset:
U‐Pin Polyamide Motif for Recognition of the DNA Minor Groove
Authors: Heckel Alexander , Dervan Peter B. 
Published: July 2003

AbstractDNA‐binding hairpin pyrrole–imidazole polyamides with γ‐aminobutyric acid as a turn‐forming residue tolerate A⋅T or T⋅A base pairs under the turn. U‐pins—polyamides with a different turn—have been synthesized and their DNA binding properties were studied. The two turn‐forming residues are connected via the ring nitrogens using variable length aliphatic linkers ((CH2)n, n=3–6). Through optimization of the linker length and the substituents at the 2‐position of the pyrrole residue on the U‐turn, polyamides with G⋅C/C⋅G tolerant turns could be found, which bind to DNA in a predictable manner.
New Molecular Topologies by Fourfold Metathesis Reactions within a Hydrogen‐Bonded Calix[4]arene Dimer
Authors: Vysotsky Myroslav O. , Bolte Michael , Thondorf Iris , Böhmer Volker 
Published: July 2003

AbstractA calix[4]arene tetrapentyl ether in the cone conformation substituted at its wide rim by four m‐(ω‐octenyloxy)phenyl urea groups forms hydrogen‐bonded dimeric capsules in dichloromethane/benzene (95:5). Metathesis reaction with Grubbs' catalyst under high‐dilution conditions (1.1×10−4 M) followed by hydrogenation leads to a covalent connection of all the urea groups within a dimer. Three topologically different products may be expected in such a reaction: a bis[2]catenane, a doubly bridged monocatenane and a tetrabridged capsule. All three possible reaction products could be isolated in an overall yield up to 60 % for the separated and purified compounds. Their identification was based on the NMR patterns which reflect the characteristic symmetry properties of the isomeric products especially in the region of the hydrogen‐bonded NH protons and were further confirmed by MALDI‐TOF mass spectra. Further structural support for the bis[2]catenane comes from a single‐crystal X‐ray structure, although severe disorder prevents the localization of all atoms in the aliphatic chains connecting the two calix[4]arenes. Kinetic studies for the guest release/exchange (cyclohexane against the solvent [D6]benzene) do not show remarkable differences between the starting dimer and the additionally linked dimers, while the mobility of an included tetraethylammonium cation is obviously more restricted.
On the Total Synthesis and Determination of the Absolute Configuration of Rishirilide B: Exploitation of Subtle Effects to Control the Sense of Cycloaddition of o‐Quinodimethides
Authors: Yamamoto Kana , Hentemann Martin F. , Allen John G. , Danishefsky Samuel J. 
Published: July 2003

AbstractThe total synthesis of racemic rishirilide B has been accomplished. The synthesis serves to define the relative relationships of its stereogenic centers. Also, starting with readily available chiral pool, ent‐rishirilide B was synthesized, thereby demonstrating that natural configuration of rishirilide B. The defining step in our total synthesis is the facile cycloreversion of the bis(siloxy)benzocyclobutane and the intermolecular o‐quinodimethide Diels–Alder cycloaddition. We believe that the tight regiochemical guidance in this step arises from a meshing of the electron‐donating effects of the symmetry‐perturbing aromatic OTBS group of the o‐quinodimethide diene with the reactivity differential of the dienophile (enedione), modulated by the hydroxyl group at the α‐position. The validity of the hypothesis of hydroxy‐directed activation of its vicinal ketone function in the context of the enedione dienophile warrants further study. This type of activation may find broader applications in distinguishing reactivity profiles of key closely related functional groups in organic substrates.
Orthopalladated and ‐platinated Bulky Triarylphosphite Complexes: Synthesis, Reactivity and Application as High‐Activity Catalysts for Suzuki and Stille Coupling Reactions
Authors: Bedford Robin B. , Hazelwood (néeWelch) Samantha L. , Limmert Michael E. , Albisson David A. , Draper Sylvia M. , Scully P. Noelle , Coles Simon J. , Hursthouse Michael B. 
Published: July 2003

AbstractBulky triarylphosphite ligands undergo facile orthometallation reactions with palladium and platinum precursors. The crystal structure of an example of the resultant palladacycles has been determined. The reactivity of some of the metallacycles with HCl, monodentate and bidentate phosphines and sodium diethyldithiocarbamate has been investigated, and the crystal structure of a diethyldithiocarbamate adduct of a palladacycle is presented. The palladacyclic complexes prove to be extremely active catalysts for the Suzuki coupling of aryl bromides with aryl boronic acids. They can also be used as catalysts for the coupling of alkylboronic acids. Meanwhile di‐ and trialkyl phosphine adducts of one of the palladacycles shows very high activity in the Suzuki coupling of aryl chlorides and can also be used to good effect for the Stille coupling of these substrates. The role of the phosphite ligand in the Suzuki coupling of aryl chlorides seems to be one of increasing catalyst longevity by stabilisation of the Pd0 resting state.
Allenes as Carbon Nucleophiles in Intramolecular Attack on (π‐1,3‐Diene)palladium Complexes: Evidence for trans Carbopalladation of the 1,3‐Diene
Authors: Dorange Ismet , Löfstedt Joakim , Närhi Katja , Franzén Johan , Bäckvall Jan‐E. 
Published: July 2003

AbstractReaction of allene‐substituted cyclohexa‐ and cyclohepta‐1,3‐dienes with [PdCl2(PhCN)2] gave η3‐(1,2,3)‐cyclohexenyl‐ and η3‐(1,2,3)‐cycloheptenylpalladium complexes, respectively, in which CC bond formation between the allene and the 1,3‐diene has occurred. Analysis of the (π‐allyl)palladium complexes by NMR spectroscopy, using reporter ligands, shows that the CC bond formation has occurred by a trans carbopalladation involving nucleophilic attack by the middle carbon atom of the allene on a (π‐diene)palladium(II) complex. The stereochemistry of the (π‐allyl)palladium complexes was confirmed by benzoquinone‐induced stereoselective transformations to allylic acetates.
Cover Picture: U‐Pin Polyamide Motif for Recognition of the DNA Minor Groove (Chem. Eur. J. 14/2003)
Authors: Heckel Alexander , Dervan Peter B. 
Published: July 2003

AbstractThe cover picture shows a DNA double helix with a pyrrole/imidazole‐polyamide bound to the minor groove. The hydrogen bond recognition pattern for the edges of the four Watson–Crick base pairs on the floor of the DNA minor groove is represented as a series of dips and bumps which are read by the corresponding bumps and dips on the edges of four ring pairs of the polyamide. These building blocks can also be seen on the table and the illustration in the back shows the selection rules. The DNA‐bound polyamide is a U‐pin with a G/C‐tolerant turn. For details about this new polyamide motif see the report by P. B. Dervan et al. on p. 3353 ff.
Retinal remodeling triggered by photoreceptor degenerations
Authors: Jones Bryan W. , Watt Carl B. , Frederick Jeanne M. , Baehr Wolfgang , Chen Ching‐Kang , Levine Edward M. , Milam Ann H. , Lavail Matthew M. , Marc Robert E. 
Published: July 2003

AbstractMany photoreceptor degenerations initially affect rods, secondarily leading to cone death. It has long been assumed that the surviving neural retina is largely resistant to this sensory deafferentation. New evidence from fast retinal degenerations reveals that subtle plasticities in neuronal form and connectivity emerge early in disease. By screening mature natural, transgenic, and knockout retinal degeneration models with computational molecular phenotyping, we have found an extended late phase of negative remodeling that radically changes retinal structure. Three major transformations emerge: 1) Müller cell hypertrophy and elaboration of a distal glial seal between retina and the choroid/retinal pigmented epithelium; 2) apparent neuronal migration along glial surfaces to ectopic sites; and 3) rewiring through evolution of complex neurite fascicles, new synaptic foci in the remnant inner nuclear layer, and new connections throughout the retina. Although some neurons die, survivors express molecular signatures characteristic of normal bipolar, amacrine, and ganglion cells. Remodeling in human and rodent retinas is independent of the initial molecular targets of retinal degenerations, including defects in the retinal pigmented epithelium, rhodopsin, or downstream phototransduction elements. Although remodeling may constrain therapeutic intervals for molecular, cellular, or bionic rescue, it suggests that the neural retina may be more plastic than previously believed. J. Comp. Neurol. 464:1–16, 2003. © 2003 Wiley‐Liss, Inc.
Single‐cell study of motor cortex projections to the barrel field in rats
Authors: Veinante Pierre , Deschênes Martin 
Published: July 2003

AbstractIn freely moving rats, whisking is associated with a slow modulation of neuronal excitability in the primary somatosensory cortex. Because it persists after the blockade of vibrissa input, it was suggested that the slow modulation might be mediated by motor–sensory corticocortical connections and perhaps result from the corollary discharges of corticofugal cells. In the present study, we identified motor cortical cells that project to the barrel field and reconstructed their axonal projections after juxtacellularly staining single cells with a biotinylated tracer. On the basis of the final destination of main axons, two groups of neurons contribute to motor–sensory projections: callosal cells (87.5%) and corticofugal cells (12.5%). Axon collaterals of callosal cells arborize in layers five to six of the granular and dysgranular zones and give off several branches that ascend between the barrels to ramify in the molecular layer. In contrast, the axon collaterals of corticofugal cells do not ramify in the infragranular layers but in layer 1. The origin of the majority of motor sensory projections from callosally projecting cells does not support the notion that the slow modulation results from the corollary discharges of corticofugal axons. It would rather originate from a separate population of cells, which could output the slow signal to the barrel field in parallel with the corticofugal commands to a brainstem pattern generator. As free whisking is characterized by bilateral concerted movements of the vibrissae, the transcallosal contribution of motor–sensory axons represents a substrate for synchronizing the slow modulation across both hemispheres. J. Comp. Neurol. 464:98–103, 2003. © 2003 Wiley‐Liss, Inc.
The negative impact of perceiving discrimination on collective well‐being: the mediating role of perceived ingroup status
Authors: Leonardelli Geoffrey J. , Tormala Zakary L. 
Published: July 2003

AbstractPrevious research has found that, among stigmatized group members, perceiving discrimination against the ingroup simultaneously yields a positive indirect effect on self‐worth (mediated by ingroup identification) and a negative direct effect (Branscombe, Schmitt, & Harvey, 1999). This study not only replicated these effects with a sample of women, but also revealed that the negative direct effect was mediated by perceived status of the ingroup: as perceived discrimination increased, perceived ingroup status decreased, which in turn lowered collective self‐worth. Perceiving discrimination also increased the accessibility of the stigmatized group's devalued status. A new direction for future research may be to consider when stigmatized group members might affirm the ingroup rather than protect self‐worth. Copyright © 2003 John Wiley & Sons, Ltd.
Cognitive dissonance, double forced compliance, and commitment
Authors: Joule Robert‐Vincent , Azdia Touati 
Published: July 2003

AbstractDouble forced compliance situations are studied to analyse how attitudes change after the performance of two behaviours, rather than just one as in standard forced (or induced) compliance situations. In the present experiment, subjects were asked to execute two successive counterattitudinal behaviours: writing an essay in favour of selective admission to the third year of university (first behaviour) and giving a convincing speech in favour of selective admission (second behaviour). The first behaviour was always performed in a high‐commitment context (free choice, publicness, and consequences), whereas the second was performed in a high‐commitment context as well as in a low‐commitment context (free choice, anonymity, and no consequences). The following hypotheses were tested. (1) If the second behaviour is performed in a high‐commitment context, it will increase the dissonance induced by the first. (2) If the second behaviour is performed in a low‐commitment context, it will decrease the dissonance induced by the first. The results confirmed both hypotheses, which comply with the radical version of dissonance theory (Beauvois & Joule, 1996, 1999). As a whole, these results are incompatible with competing theories of Festinger's theory of dissonance (1957), and in particular with self‐perception and impression‐management theories. Copyright © 2003 John Wiley & Sons, Ltd.
Non‐linear forecasts of stock returns
Authors: Kanas Angelos 
Published: July 2003

AbstractFollowing recent non‐linear extensions of the present‐value model, this paper examines the out‐of‐sample forecast performance of two parametric and two non‐parametric nonlinear models of stock returns. The parametric models include the standard regime switching and the Markov regime switching, whereas the non‐parametric are the nearest‐neighbour and the artificial neural network models. We focused on the US stock market using annual observations spanning the period 1872–1999. Evaluation of forecasts was based on two criteria, namely forecast accuracy and forecast encompassing. In terms of accuracy, the Markov and the artificial neural network models produce at least as accurate forecasts as the other models. In terms of encompassing, the Markov model outperforms all the others. Overall, both criteria suggest that the Markov regime switching model is the most preferable non‐linear empirical extension of the present‐value model for out‐of‐sample stock return forecasting. Copyright © 2003 John Wiley & Sons, Ltd.
Selection of Value‐at‐Risk models
Authors: Sarma Mandira , Thomas Susan , Shah Ajay 
Published: July 2003

AbstractValue‐at‐Risk (VaR) is widely used as a tool for measuring the market risk of asset portfolios. However, alternative VaR implementations are known to yield fairly different VaR forecasts. Hence, every use of VaR requires choosing among alternative forecasting models. This paper undertakes two case studies in model selection, for the S&P 500 index and India's NSE‐50 index, at the 95% and 99% levels. We employ a two‐stage model selection procedure. In the first stage we test a class of models for statistical accuracy. If multiple models survive rejection with the tests, we perform a second stage filtering of the surviving models using subjective loss functions. This two‐stage model selection procedure does prove to be useful in choosing a VaR model, while only incompletely addressing the problem. These case studies give us some evidence about the strengths and limitations of present knowledge on estimation and testing for VaR. Copyright © 2003 John Wiley & Sons, Ltd.
Transport of glutathione conjugates and chemotherapeutic drugs by RLIP76 (RALBP1): A novel link between G‐protein and tyrosine kinase signaling and drug resistance
Authors: Awasthi Sanjay , Singhal Sharad S. , Sharma Rajendra , Zimniak Piotr , Awasthi Yogesh C. 
Published: July 2003

AbstractOur studies have shown that RLIP76 (RALBP1), a 76 kDa Ral‐binding, Rho/Rac‐GAP and Ral effector protein, is a novel multispecific transporter of xenobiotics as well as GS‐Es. Like previously characterized ABC transporters, it mediates ATP‐dependent transport of structurally unrelated amphiphilic xenobiotics and displays inherent ATPase activity, which is stimulated by its substrate allocrites. It does not have significant sequence homology with ABC transporters and differs from the ABC transporters in several other important aspects, including (i) lack of any close homologs in humans, (ii) lack of a classical Walker domain, (iii) integral membrane association without clearly defined transmembrane domains and (iv) its role as a direct link to Ras/Ral/Rho and EGF‐R signaling through its multifunctional nature, including GAP activity, regulation of exocytosis as well as clathrin‐coated pit–mediated receptor endocytosis. Its multifunctional nature derives from the presence of multiple motifs, including a Rho/Rac GAP domain, a Ral effector domain binding motif, 2 distinct ATP‐binding domains, a H+‐ATPase domain, PKC and tyrosine kinase phosphorylation sites and the ability to undergo fragmentation into multiple smaller peptides which participate as components of macromolecular functional complexes. One of the physiologic functions of RLIP76 is regulation of intracellular concentration of the electrophilic intermediates of oxidative lipid metabolism by mediating efflux of GS‐E formed from oxidative degradation of arachidonic acid, including leukotrienes and the 4HNE‐GSH conjugate. RLIP76‐mediated transport of amphiphilic chemotherapeutic agents such as anthracyclines and vinca alkaloids as well as GS‐E produced during oxidative metabolism places this multifunctional protein in a central role as a resistance mechanism for preventing apoptosis caused by chemotherapeutic agents and a variety of external/internal stressors, including oxidative stress, heat shock and radiation. © 2003 Wiley‐Liss, Inc.
Acceleration of tumor growth and peri‐tumoral blood clotting by imatinib mesylate (Gleevec™)
Authors: Samoszuk Michael , Corwin Mark A. 
Published: July 2003

AbstractImatinib mesylate (Gleevec™) inhibits the BCR‐ABL tyrosine kinase in chronic granulocytic leukemia. Previous studies have demonstrated that imatinib mesylate also inhibits the survival and functions of normal mast cells by interfering with the receptor tyrosine kinase for stem cell factor (SCF), c‐kit, which is expressed by mast cells. Because mast cells extensively surround many types of cancer and contain powerful anticoagulants such as heparin, we investigated the effects of imatinib mesylate on blood clotting and tumor growth within subcutaneous implants of a mammary adenocarcinoma cell line (4T1) in BALB/c mice. After 5 days of oral treatment with 10 mg/kg of the drug, the average mass of the tumors in treated mice (198 ± 42 mg, n = 5) was significantly (p < 0.05) greater than the average mass of the tumors from untreated (control) mice (60 ± 23 mg, n = 5). Moreover, the tumors in the treated mice were frequently surrounded by large lakes of clotted blood that were not evident in tumors from the control mice. Accelerated growth and blood clotting were also observed in tumor‐bearing mice treated with heparinase I enzyme to destroy endogenous mast cell heparin and in NDST‐2 knockout mice in which there is a targeted disruption in the gene coding for mast cell heparin synthesis. We conclude that imatinib mesylate accelerated the growth and peri‐tumoral blood clotting of implants of mammary adenocarcinoma in mice. These results suggest that imatinib mesylate may have significant effects on mast cells infiltrating tumors, in addition to its other biologic activities. Our results also indicate that the mechanism of this effect may be related to the anticoagulant properties of mast cell heparin. © 2003 Wiley‐Liss, Inc.
Stromelysin‐1/matrix metalloproteinase‐3 (MMP‐3) expression accounts for invasive properties of human astrocytoma cell lines
Authors: Mercapide Javier , Lopez De Cicco Ricardo , Castresana Javier S. , Klein‐Szanto Andres J.P. 
Published: July 2003

AbstractTumor invasiveness is an intrinsic feature of most glial tumors that accounts for their malignant and locally destructive nature. We evaluated the subcutaneous (sc) tumorigenicity and in vivo invasiveness of 9 astrocytoma cell lines together with their respective metalloprotease activity in order to establish their biologic behavior and malignant potential. Invasiveness was assessed with an in vivo invasion assay using tracheal xenotransplants subcutaneously implanted into Scid mice. This assay permitted us to evaluate the penetration of tumor cells into the transplanted deepithelialized tracheas previously inoculated with either normal primary glial cells or with astrocytoma‐derived cell lines. Although only 2 cell lines were tumorigenic after sc inoculation, 5 out of 9 tumor cell lines were tumorigenic in the tracheal graft system. The astrocytoma cell lines showed varying levels of penetration into the tracheal wall. The tumor lines GOS3, M059K, CCFSTTG1 and A172, as well as primary normal astrocytes, were nontumorigenic and noninvasive in this experimental model. LN405, SW1088 and SW1783 cells that were not tumorigenic as sc xenotransplants, on the other hand, grew well in the tracheal graft system showing low levels of in vivo invasiveness. U87MG and U118MG cells were tumorigenic as sc xenotransplants and showed high levels of invasiveness. In parallel to these in vivo studies, the constitutive levels of secreted gelatinases and stromelysins (MMP‐3 and MMP‐11) were investigated using conditioned media submitted to gelatin or casein‐substrate zymography and Western blot analysis. Neither the gelatinases (MMP‐2 and MMP‐9) nor MMP‐11 showed a direct correlation with the levels of in vivo tumor cell invasiveness. Conversely, secretion of MMP‐3 correlated closely with tumorigenicity and invasiveness. In vitro tumor cell invasiveness was significantly reduced after incubation with the metalloproteinase inhibitor GM6001. This positive correlation between MMP‐3 and the depth of tracheal wall penetration led us to conclude that the invasive properties of brain tumor cells may be due to the direct or indirect proteolytic effects of MMP‐3 on extracellular matrix (ECM) macromolecules and that this enzyme might be a potential target for future therapies. © 2003 Wiley‐Liss, Inc.
Time trends in cancer mortality in China: 1987–1999
Authors: Yang Ling , Parkin Donald M. , Li Liandi , Chen Yude 
Published: July 2003

AbstractA first analysis of time trends in cancer mortality in China at the national level is presented. Using a joinpoint regression model, based on data from a national mortality routine reporting system in China (CHIS), time trends in mortality for 9 major cancers are analyzed. Between 1987 and 1999, the age‐standardized mortality rates for all cancers combined declined slightly in rural areas but have increased since 1996 in urban areas. The mortality rates for cancers in oesophagus, stomach, cervix uteri, leukaemia (except for urban males after 1996) and nasopharynx declined, while lung cancer and female breast cancer showed significant increasing trends in both urban and rural areas and for both sexes. Cancers of the colon‐rectum and liver had different trends in mortality in urban and rural populations. The trends in age‐specific mortality rates suggest some different trends in the younger population, which may presage future overall trends, for example, increasing mortality from cancer of the cervix. The observed trends primarily reflect the dramatic changes in socioeconomic circumstances and lifestyles in China in the last 2 decades. Tobacco smoking remains a major problem, with increases in mortality from lung cancer. The improvements in socioeconomic status, diet and nutrition may be responsible for the declining risk of some cancers (oesophagus, stomach and nasopharynx), while increasing the risk for others (breast and colon‐rectum). Screening programs (especially for cervix cancer), and more available and better facilities for cancer therapy, may have helped to reduce mortality for several cancers. The large increases in the absolute number of deaths that resulted from the increasing and aging population are much more important in determining the future cancer burden than any changes due to change in risk, emphasizing the increasing importance of cancer as a health problem in the 21st century in China. © 2003 Wiley‐Liss, Inc.