bluuebunny/crossref_metadata_2025 huggingface dataset:
P2X7 Receptor‐induced generation of reactive oxygen species in rat mesangial cells
Authors: Harada H. , Tsukimoto M. , Ikari A. , Takagi K. , Suketa Y.
Published: May 2003

Apoptosis of mesangial cells is an important mode of cell death that maintains normal morphology and function within the glomerulus during development and in normal cell turnover; it is also important in pathological processes. Stimulation of rat mesangial cells via P2X7 receptors can induce apoptotic cell death. However, the signaling pathways are not well understood. Recently, Suh et al. reported P2X7 receptor‐mediated generation of reactive oxygen species (ROS). Generations of ROS have been linked to induction of apoptosis. In this study, we characterized the P2X7 receptor‐induced ROS generation in rat mesangial cells. P2X7 agonist, 2′ and 3′‐O‐(4‐benzoyl) benzoyl‐ATP (BzATP) evoked ROS generation in a concentration‐dependent manner. The profile of ROS generation in response to BzATP was characteristic of the activation of NADPH oxidase. We could also detect BzATP‐induced production of peroxynitrite. These results suggested that the superoxide anion was generated primarily, and then it rapidly reacted with endogenous nitric oxide, yielding peroxynitrite. The generation of ROS in rat mesangial cells may contribute to P2X7 receptor‐induced apoptotic cell death. Drug Dev. Res. 59: 112–117, 2003. © 2003 Wiley‐Liss, Inc.
Involvement of P2X2 and P2X3 receptors in neuropathic pain in a mouse model of chronic constriction injury
Authors: Ueno Shinya , Moriyama Tomoko , Honda Kenji , Kamiya Hiro‐o , Sakurada Tsukasa , Katsuragi Takeshi
Published: May 2003

In the present study, we examined the involvement of P2X receptors in neuropathic pain using the chronic constriction injury (CCI) model. The thermal and mechanical nociceptive thresholds were evaluated using the paw withdrawal test and a von Frey test, respectively. Also, the expression of P2X receptors in the dorsal root ganglia (DRG) was analyzed using quantitative real‐time RT‐PCR. In the acute stage of CCI (3–30 days after injury), thermal hyperalgesia and mechanical allodynia had developed and mRNA of P2X2 and P2X3 was upregulated in the ipsilateral DRG. The thermal hyperalgesia at 7 days was inhibited by intrathecal (i.t.) administration of P2X antagonists, pyridoxal‐phosphate‐6‐azophenyl‐2′,4′‐disulfonate (PPADS), 2′‐O‐(trinitrophenyl)adenosine 5′‐triphosphate, trisodium salt (TNP‐ATP) and diinosine pentaphosphate (IP5I). In contrast, mechanical allodynia (7 days) was inhibited by the i.t. administration of PPADS and TNP‐ATP but not IP5I. These pharmacological and gene expression data suggest that upregulated homomeric P2X3 and heteromeric P2X2 and P2X3 (P2X2/3) receptors augmented thermal hyperalgesia and mechanical allodynia, respectively, at the spinal level in acute stage of CCI. In the chronic stage (>40 days), thermal hyperalgesia disappeared but the mechanical allodynia persisted. Only P2X3 mRNA was downregulated. PPADS and TNP‐ATP failed to restore the mechanical threshold to the normal level. These data suggest that the involvement of P2X receptors changed in the chronic stage of CCI. Drug Dev. Res. 59:104–111, 2003. © 2003 Wiley‐Liss, Inc.
Purinergic P2X7 receptor function in lung alveolar macrophages: Pharmacologic characterization and bidirectional regulation by Th1 and Th2 cytokines
Authors: Lemaire Irma , Leduc Natacha
Published: May 2003

Purinergic P2X7 receptors have been shown in the lung, but little is known concerning P2X7 function in pulmonary macrophages. In this study we characterized P2X7‐dependent responses to extracellular ATP in resident and activated alveolar macrophages (AM) obtained by bronchoalveolar lavage of rats. Incubation of AM with high concentrations of ATP (5mM) or 3′‐O‐(4‐benzoyl)benzoyl‐ATP (BzATP) (0.5mM), a P2X7 agonist, induced: 1) rapid pore formation, 2) apoptosis, and 3) enhanced release of IL‐1α, IL‐1β, and IL‐6, but not TNF‐α following priming with lipopolysaccharide (LPS). Furthermore, higher expression of P2X7 receptor in AM was associated with increased formation of Type 2 multinucleated giant cells (Type 2 MGC) in response to GMCSF. Immunopharmacological analysis also showed that P2X7‐dependent pore formation in AM was significantly increased by LPS (1 µg/ml) and the T helper 1 (Th1) cytokines, interferon‐γ (100U/ml), and, to a lesser extent, TNF‐α (>20 ng/ml). In contrast, the T helper 2 (Th2) cytokines IL‐4 (1pg/ml) as well as IL‐10 (1ng/ml) significantly inhibited these P2X7 receptor functions. Transforming growth factor‐β (TGF‐β), a known deactivator of macrophages, had no significant effect. Our results demonstrate that AM exhibit all the characteristics of a functional P2X7 receptor which upon appropriate stimulation activates the proinflammatory IL‐1→IL‐6 cytokine cascade and the formation of MGC, a hallmark of granulomatous reactions. Moreover, Th1 and Th2 cytokines reciprocally regulate P2X7 function, suggesting a role for P2X7 in pulmonary diseases associated with chronic inflammatory responses. Drug Dev. Res. 59:118–127, 2003. © 2003 Wiley‐Liss, Inc.
Gene knockout approach to adenosine A2A receptors in Parkinson's disease
Authors: Chen Jiang‐Fan , Schwarzschild Michael A.
Published: May 2003

Recently, the adenosine A2A receptor (A2AR) has emerged as an attractive target for Parkinson's disease (PD) treatment by virtue of its coexpression with the dopamine D2 receptor (D2R) in the striatum and its modulation of dopamine receptor‐mediated functions. Moreover, the adenosine antagonist, caffeine, has recently been linked to a reduced risk of developing PD in large prospective epidemiological studies, raising the possibility that caffeine and more specific adenosine antagonists may protect against dopaminergic neuron death. Recently, we and others have developed a series of A2AR and D2R knockout (KO) mouse models. These mutant mouse models with complete, specific genetic inactivation of A2ARs and D2Rs overcome some of the intrinsic limitations of A2A antagonists and provide an opportunity to investigate A2AR's role in the development and treatment of PD. First, we used D2 as well as A2AR KO mice to dissect the molecular mechanism of the A2AR's action by determining the dependence of A2AR function on D2 receptors. The A2A antagonist (CSC) and the nonspecific antagonist caffeine induced motor stimulation in naive and reserpinized mice deficient in D2 receptor. These results suggest that A2AR antagonists enhance motor function at least partially independent of D2 receptors. Second, we explored the role of A2ARs in the development of L‐dopa‐induced behavioral sensitization in unilaterally 6‐hydroxydopamine‐lesioned mice, an animal model of the behavioral and neurochemical features of dyskinesia in PD. Genetic inactivation of A2ARs markedly attenuated the development and persistence of L‐dopa‐induced rotational behavioral sensitization and attenuated induction of dynorphin mRNA in the striatum. The results suggest that A2AR plays a critical role in the development of persistent maladaptive dyskinetic responses to chronic L‐dopa treatment in PD. Finally, we showed that genetic inactivation of A2ARs attenuates MPTP‐induced depletion of dopamine and dopamine transporter (DAT) in the striatum and loss of dopaminergic neurons in the substantia nigra. Together, these results obtained with genetic approaches demonstrate that A2AR inactivation may have multiple therapeutic benefits for PD: motor enhancement through a partial D2‐independent mechanism, prevention of L‐dopa‐induced behavioral sensitization, and attenuation of dopaminergic neurodegeneration. The generation of tissue‐specific and inducible A2A KO mouse models will further refine our understanding of the A2A receptor's role in the development and treatment of PD. Drug Dev. Res. 58:354–367, 2003. © 2003 Wiley‐Liss, Inc.
Immunoreactivity for glial fibrillary acidic protein and P2 receptor expression on astrocytes in vivo
Authors: Franke Heike , Krügel Ute , Grosche Jens , Illes Peter
Published: May 2003

Changes in glial fibrillary acidic protein (GFAP) are believed to be a sensitive and specific marker for astroglial responses to various kinds of injury. Neurotrophic factors and their receptors involved in the physiological and pathological responses of astrocytes are of special interest. For example, ATP, released from damaged or dying cells, may represent one of the endogenous factors mediating the activation of astrocytes. In the present study, the influence of different ATP analogs on the GFAP‐immunoreactivity (IR) and on the expression of P2 receptors on GFAP‐labeled cells were studied. Microinjection of the selective P2 receptor agonists α,β‐methylene ATP (α,β‐meATP; P2X1,3), adenosine 5′‐O‐(2‐thiodiphosphate) (ADP‐β‐S; P2Y1,12), and uridine 5′‐O‐(3‐thiotriphosphate) (UTP‐γ‐S; P2Y2,4,6) in the nucleus accumbens (NAc) of rats resulted in an increase of GFAP‐IR in comparison to the treatment with artificial cerebrospinal fluid. The agonist‐induced morphogenic changes documented a strong potency of α,β‐meATP and ADP‐β‐S. The effect of UTP‐γ‐S was small. Blockade of P2 receptors with the nonselective antagonist pyridoxalphosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS) decreased the injury‐induced elevation of GFAP‐IR when given alone and in addition inhibited the agonist effects. Double immunofluorescence measurements confined the localization of P2X2–4 and P2Y1 receptor subtypes to GFAP‐labeled astrocytes of untreated rats. The receptor subtypes P2X1,5,7 were not present in the NAc of native rats, but became expressed after mechanical damage. P2X6 receptor‐labeling was absent both with and without mechanical damage. After microinjection of α,β‐meATP and ADP‐β‐S into the NAc, the P2X1,3‐ and P2Y1‐IR, respectively, appeared to increase. These results show that the stimulation of P2 receptors influences the expression of GFAP‐IR in vivo. GFAP‐positive astrocytes possess P2X as well as P2Y receptor subtypes and change the expression of these receptors after injury and subsequent long‐term activation by ATP. Drug Dev. Res. 59:175–189, 2003. © 2003 Wiley‐Liss, Inc.
Proliferating intestinal γ/δ T cells recirculate rapidly and are a major source of the γ/δ T cell pool in the peripheral blood
Authors: Thielke Karl‐Heinz , Hoffmann‐Moujahid Astrid , Weisser Clemens , Waldkirch Eginhard , Pabst Reinhard , Holtmeier Wolfgang , Rothkötter Hermann J.
Published: May 2003

The proliferation, recirculation and repertoire of gut‐derived γ/δ T cells were studied in pigs in vivo. Proliferating γ/δ T cells (detected by BrdU labeling) are present in all intestinal compartments. In the gut lymph ∼0.5% of all γ/δ T cells were proliferating. These gut‐derived BrdU+ γ/δ T cells re‐enter the intestinal tissues, and re‐appear in the intestinal lymph far more often than other cells: about 22% of i.v.‐injected BrdU+ γ/δ T cells were recovered again from the intestinal lymph within 72 h (compare with BrdU+ B cells 2%, and other BrdU+ T cells 10%). The contribution of the gut to the migrating γ/δ T cell pool in the blood became obvious: the proportion of BrdU+ γ/δ T cells was three‐times larger in control versus cannulated pigs. In 9‐month‐old pigs, clonally expanded T cells were identified in the intestine by complementarity‐determining region 3 spectratyping of TCR‐δ transcripts. Such expansions were not visible in the blood or intestinal lymph. The distribution of γ/δ T cells within the intestinal tract is likely to depend to a large degree on the proliferation and the migratory properties of these cells which are different to those of α/β T cells and B lymphocytes.
Longitudinal analysis of Mycobacterium tuberculosis 19‐kDa antigen‐specific T cells in patients with pulmonary tuberculosis: association with disease activity and cross‐reactivity to a peptide from HIVenv gp120
Authors: Höhn Hanni , Kortsik Cornelius , Tully Glenn , Nilges Katja , Necker Antje , Freitag Kirsten , Neukirch Claudia , Galle Peter , Löhr Hans , Maeurer Markus J.
Published: May 2003

CD8+ T cells play a central role in immune protection against infection with Mycobacterium tuberculosis. One of the target epitopes for anti‐M. tuberculosis directedCD8+ T cells is the HLA‐A2‐restricted 19‐kDa lipoprotein peptide VLTDGNPPEV. T cell clones directed against this epitope recognized not only the nominal peptide ligand, but also a closely related peptide (VPTDPNPPEV) from the HIV envelope gp120 (HIVenv gp120) protein characterized by IFN‐γ release. This cross‐reactivity was confirmed in ex vivo in M. tuberculosis 19‐kDa tetramer‐sorted T cells from patients with tuberculosis and in HIVgp120 tetramer‐reactive T cells sorted from HIV+ patients. M. tuberculosis 19‐kDa antigen‐reactive T cells were present in HLA‐A2+ patients (10/10) with HIV infection with no evidence of M. tuberculosis infection, but they are absent in peripheral blood lymphocytes from healthy HLA‐A2+ individuals (10/10). M. tuberculosis 19‐kDa antigen‐reactive T cells were elevated in acute pulmonary tuberculosis, declined with response to therapy (7/10 patients) and resided in the terminally differentiated CD8+ T cell subset. CD8+ cross‐reactive T cells recognizing HIVenv or M. tuberculosis 19‐kDa antigens may contribute to pathogenesis in individuals co‐infected with both pathogens and may also present a marker for active tuberculosis.
PU.1 is required for transcriptional activation of the Stat6 response element in the Igϵ promoter
Authors: Pesu Marko , Aittomäki Saara , Välineva Tuuli , Silvennoinen Olli
Published: May 2003

Signal transducer and activator of transcription 6 (Stat6) has a crucial role in regulation of IL‐4‐induced gene responses. Stat6‐binding sites are present in the promoters of both ubiquitously and cell‐type‐specifically expressed genes. The promoter regions of IL‐4‐inducible genes contain cis‐acting elements for several transcription factors that act in concert with Stat6 and are also likely to modulate lineage‐specific gene expression. We have observed that the Stat6 response element from the B‐cell‐specific Igϵ promoter is readily activated upon IL‐4 stimulation in B cells but not in non‐hematopoietic cells. A minimal low‐affinity PU.1‐core‐binding sequence (5′‐AGAA‐3′) was identified within the Stat6 DNA‐binding site in the Igϵ promoter. Ectopic expression of the myeloid‐ and B‐cell‐specific transcription factor PU.1 restored the IL‐4‐inducibility of the Igϵ‐Stat6 response element in HepG2 cells, and the induction required an intact PU.1‐binding sequence. Both the transactivation and the DNA‐binding domains of PU.1 were required for induction of Stat6‐mediated transcription. The co‐operation between PU.1 and Stat6 in transactivation of the Igϵ gene represents a molecular mechanism for the fine‐tuning of cell‐type‐restricted expression of IL‐4‐induced gene responses.
MUC1‐derived glycopeptide libraries with improved MHC anchors are strong antigens and prime mouse T cells for proliferative responses to lysates of human breast cancer tissue
Authors: Gad Monika , Jensen Teis , Gagne Rod , Komba Shiro , Daugaard Søren , Kroman Niels , Meldal Morten , Werdelin Ole
Published: May 2003

Multi‐component glycopeptide libraries and single glycopeptides were used for immunization of mice with the aim of inducing strong T helper cell responses to the repetitive sequence of MUC1 expressed by human tumor cells. The glycopeptides and glycopeptide libraries were modeled upon the native human MUC1 amino acid variable number of tandem repeats sequence by introduction of modifications in the MHC anchor positions to optimally fulfil the binding requirements of the Ad MHC class II molecule in the BALB/c mouse. The immunogenicity of the MUC1 glycopeptides in BALB/c micewas determined by immunization in complete Freund's adjuvant and assaying lymph node T cells for a proliferative response to the glycopeptide used. Strong proliferative responses with stimulation indices over 50 were obtained with anchor‐improved glycopeptide libraries as well as with single glycopeptides. Immunization with one of the glycopeptide libraries primed T cells for a proliferative cross‐response to the native MUC1 glycopeptide, which by itself was nonimmunogenic. In addition, immunization with the same glycopeptide library primed T cells for a strong response to lysate of a MUC1‐expressing human breast cancer, and immunization with the tumor lysate primed T cells for a response to the glycopeptide library. The T cells responding in the assay for proliferation were restricted to the Ad MHC class II molecule. The results indicate that immunization with MHC anchor‐improved MUC1 glycopeptide libraries can effectively prime T helper cells and may induce long‐term memory. The approach may be useful in the design of preventive cancer vaccines for use in humans.
Impaired contact hypersensitivity in macrophage migration inhibitory factor‐deficient mice
Authors: Shimizu Tadamichi , Abe Riichiro , Nishihira Jun , Shibaki Akihiko , Watanabe Hirokazu , Nakayama Toshinori , Taniguchi Masaru , Ishibashi Teruo , Shimizu Hiroshi
Published: May 2003

To determine whether macrophage migration inhibitory factor (MIF) is required for contact hypersensitivity (CHS) response, MIF‐deficient (MIF KO) and wild‐type (WT) mice were sensitized with trinitrochlorobenzene (TNCB) or oxazolone on their abdominal skin and challenged on the dorsum skin of one ear 5 days later. Significant ear swelling was observed in the WT mice, but this response was inhibited in the MIF KO mice (p<0.01 for MIF KO vs. WT mice in 24 h). In addition, lymph node cells from hapten‐sensitized MIF KO mice showed a decreased capacity for transferring the CHS response. A topical application of TNCB (200 μg) caused a significant decline in epidermal Langerhans cell (LC) density (20.3%; p<0.01 compared with vehicle) 4 h after application in WT mice, but it failed to provoke a significant epidermal LC migration in MIF KO mice (7.4%). By mixed lymphocyte reaction, the T cell proliferative response to alloantigen was significantly decreased in the MIF KO mice compared with WT mice (p<0.005). Taken together, these results indicate that MIF is pivotal in the regulation of cutaneous immune responses and plays a central role in LC migration and T cell proliferation for the CHS response.
Epstein‐Barr virus (EBV)‐positive lymphoproliferations in post‐transplant patients show immunoglobulin V gene mutation patterns suggesting interference of EBV with normal B cell differentiation processes
Authors: Bräuninger Andreas , Spieker Tilmann , Mottok Anja , Baur Audrey Sylvia , Küppers Ralf , Hansmann Martin‐Leo
Published: May 2003

In a model for persistent infection, Epstein‐Barr virus (EBV) uses the germinal center (GC) reaction to establish persistence in memory B cells. To study whether EBV adopts to normal B cell differentiation processes also in EBV‐associated lymphoproliferative diseases, we micromanipulated EBV+ cells from biopsies of five patients with post‐transplantation lymphoproliferative disease (PTLD) and one unusual Hodgkin lymphoma with many small EBV+ cells, and analyzed rearranged V genes of single cells. In all cases clonal expansions of EBV+ B cells were identified. The vast majority of these clones carried mutated V gene rearrangements and a fraction of clones showed ongoing hypermutation. Hence, PTLD likely derive from GC and/or post‐GC B cells. In two clones hypermutation occurred in the absence of follicular dendritic and CD4+ T cells, important interaction partners of normal GC B cells. Furthermore, in one case sustained somatic hypermutation occurred without expression of a functional antigen receptor. Hence, EBV+ B cells in PTLD can retain or acquire features of GC B cells in an unphysiological setting and may continue to undergo somatic hypermutation uncoupled from normal selection processes, suggesting that EBV interferes with normal B cell differentiation and selection processes in PTLD.
Interaction of VIVO, VVO2 and CuII with a Peptide Analogue SalGly‐L‐Ala
Authors: Jakusch Tamás , Dörnyei Ágnes , Correia Isabel , Rodrigues Lígia M. , Tóth Gábor K. , Kiss Tamás , Pessoa João Costa , Marcão Susana
Published: May 2003

The formation of complexes of a tripeptide analogue, salicylglycyl‐L‐alanine [HOC6H4C(O)NHCH2C(O)NHCH(CH3)COOH, H2SalGly‐L‐Ala], was studied with CuII, VIVO and VVO2 in aqueous solution using pH‐potentiometric and spectroscopic (UV/Vis, CD, EPR and 51V NMR) techniques. The results demonstrated the ambidentate character of the ligand. The metal ion‐induced deprotonation and subsequent coordination of the two neighbouring amide groups was shown to occur in a cooperative way in the pH range 5−6. At pH ≈︁ 6.5 a complex with an (O−, 2 × CON−, COO−) binding set becomes predominant for both CuII and VIVO. The affinity of the phenolate‐O− for VIVO is high and the ligand is bound to this metal ion even at pH values greater than 10. Conversely, the affinity for VVO2 is significantly lower and no interaction between this metal oxo‐ion and the ligand could be detected in the pH range 2−12. In contrast, with the dipeptide analogue H2SalGly, chelation involving the deprotonated amide‐N− could be unambiguously detected. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Iron‐Fragment‐Substituted Heterosiloxanes of Gallium [Cp(OC)2Fe−SiR2OGaR′2]2(R, R′ = Alkyl, Aryl) − Structures of [Cp(OC)2Fe−SiR2OGaMe2]2(R = Me, Ph)
Authors: Malisch Wolfgang , Schumacher Dirk , Schmiedeskamp Bernd , Jehle Heinrich , Eisner Dirk , Schoeller Wolfgang W. , Nieger Martin
Published: May 2003

The trialkylgallanes GaR′′3[R′ = Me,iPr (2aand2b)] react with the ferrio‐silanols Cp(OC)2Fe−Si(R)(R′)OH [R = R′ = Me,iPr, Ph (1a−c), R = Me, R′ = Ph (1d)] by alkane elimination to yield the iron‐substituted siloxy‐gallanes [Cp(OC)2Fe−Si(R)(R′)OGaR′′2]2(3a−e). According to molecular mass determination in benzene (3a,3b,3d), X‐ray analyses (3a,3d) and NMR spectroscopy (3e), the novel hetero‐siloxanes exist as dimers both in solution and in the solid state. The bonding situation and geometry of the ferrio‐heterosiloxane [Cp(OC)2Fe−SiH2OGaH2]2has been analyzed by density functional calculation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Tris(pyrazolyl)methanesulfonates: More Than Just Analogues of Tris(pyrazolyl)borate Ligands; N,N,N‐, N,N,O‐, and Other Coordination Modes
Authors: Kläui Wolfgang , Berghahn Michael , Frank Walter , Reiß Guido J. , Schönherr Thomas , Rheinwald Gerd , Lang Heinrich
Published: May 2003

The thallium(I) salts of tris(pyrazolyl)methanesulfonate (Tpms) and tris(3‐tert‐butylpyrazolyl)methanesulfonate (TpmstBu) have been used to prepare the following complexes: [(TpmstBu)ZnX] [X = Cl (1a), Br (1b), I (1c), Et (3), OAc (5a)], [(TpmstBu)NiX] [X = Cl (2a), Br (2b)], [(TpmstBu)CoCl(HpztBu)] (3), [(TpmstBu)Zn(μ‐OAc)(μ‐OH)Zn(TpmstBu)] (5b), [(TpmstBu)Cu(CO)] (6a), and [(Tpms)Cu(CO)] (6b). The solid‐state structures of 1b, 2a, 3, and 5b have been determined by X‐ray analysis. The optical spectra of 2a and 3 were investigated by means of the angular overlap model to elucidate their electronic structures in view of the underlying molecular geometries. Variable‐temperature NMR and IR spectroscopic studies show that Tpms and TpmstBu can act as N,N,N and N,N,O ligands. Both coordination modes are present in solution for the zinc complexes 1a,b and the copper carbonyl complexes 6a,b. The N,N,O bonding mode is entropically favoured in solution. For the nickel complexes 2a,b, the TpmstBu ligand acts as a tripodal nitrogen ligand in the solid state and in solution. For the dinuclear zinc complex 5b, one of the TpmstBu ligands acts as an N,N,O ligand and one as an N,O ligand. Complex 5b is one of the very few structural models of the dinuclear zinc enzymes phospholipase C and phosphotriesterase. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis and Characterization of Pentaarylated [60]Fullerene Coordinated Complexes [(η2‐Ar5C60H)M(PPh3)2] (M = Pt, Pd) and an ab initio Study on Their Isomerism
Authors: Song Li‐Cheng , Liu Peng‐Chong , Hu Qing‐Mei , Lin Zhenyang , Wang Yi‐Bo
Published: May 2003

This paper reports on the first examples of η2‐pentaarylated [60]fullerene organometallic complexes [(η2‐Ar5C60H)M(PPh3)2] (1: Ar = Ph, M = Pt;2: Ar =m‐MeC6H4, M = Pt;3: Ar =p‐MeC6H4, M = Pt;4: Ar = Ph, M = Pd;5: Ar =m‐MeC6H4, M = Pd;6: Ar =p‐MeC6H4, M = Pd), which were synthesized by treatment of [M(PPh3)4] with Ar5C60H and fully characterized by elemental analyses and their1H NMR,31P NMR, IR, UV/Vis, and FAB‐MS data. The1H NMR spectra displayed by the protons directly bonded to the C60core and the31P NMR spectra caused by the PPh3ligands indicated that complexes1−6exist as mixtures of isomers. To gain insights into the isomerism of1−6, the regioselectivity of the pentaarylated derivatives Ar5C60H as ligands coordinated to Pt0or Pd0has been studied by means of ab initio calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Calculated Enthalpies for Dimerisation of Binary, Unsaturated, Main‐Group Element Hydrides as a Means to Analyse Their Potential for Multiple Bonding
Authors: Himmel Hans‐Jörg
Published: May 2003

Herein, the dimerisation of subvalent, binary, main‐group element hydrides with the potential for multiple bonding is studied using both hybrid DFT (B3LYP) and ab initio [MP2 and CCSD(T)] methods. The [2+2] cycloaddition is an important and characteristic reaction of derivatives of ethylene. A comparison of dimerisation reactions for several compounds with the potential for multiple bonding should, therefore, shed light on the properties of these species. Our study includes the hydrides E2H2 (E = B, Al, Ga, N P or As), E2H4 (E = C, Si or Ge) and ENH4 (E = B, Al or Ga) and their dimers. Several isomeric forms of the monomers and dimers have to be considered. The trends within a group and a period are established and the factors responsible for them are discussed. It turns out that, generally, the enthalpies for dimerisation increase for heavier homologues, reflecting that the most important factor is the reduced strength of the E−E bonds in the monomers prior to dimerisation and, to some degree, also the reduced ring strain in the cyclic dimers. The exceptions are the dimerisations of B2H2 and Al2H2, both of which lead to the tetrahedral E4H4 species (E = B or Al). Dimerisation of Al2H2 is associated with a smaller enthalpy than that for the dimerisation of B2H2. Comparisons and analyses are made complicated because of the changes in the structures of the isomeric global minima between homologues. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Gold, Silver and Palladium Complexes with the 2,2′‐Dipyridylamine Ligand
Authors: Burgos Mercedes , Crespo Olga , Gimeno M. Concepción , Jones Peter G. , Laguna Antonio
Published: May 2003

Reaction of the 2,2′‐dipyridylamine (Py2NH) ligand with various gold and silver starting products leads to three‐ or four‐coordinate complexes. The structure of compound [Ag(NHPy2)(PPh3)]OTf shows weak interactions which produce bands of molecules parallel to the z axis. Other hydrogen bonds of the type C−H···O serve to link the ribbons. The derivative PPN[Au(Py2N)2] has also been obtained using PPN[Au(acac)2] [PPN = bis(triphenylphosphanyl)iminio, acac = acetylacetonate] as starting product to deprotonate the ligand. The palladium complex [PdCl2(Py2NH)2] is also reported. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis, Solid‐State Structure and Multinuclear NMR Studies of the New Polyhydrido Iridium Carbonyl Cluster Ir4H4(μ‐H)4(CO)4(PPh3)4
Authors: Garlaschelli Luigi , Greco Francesco , Peli Giulia , Manassero Mario , Sansoni Mirella , Gobetto Roberto , Salassa Luca , Della Pergola Roberto
Published: May 2003

The carbonyl hydride cluster Ir4H8(CO)4(PPh3)4 (1) has been formed in high yield and purity by heating a mixture of Ir4(CO)12 and PPh3 in toluene at 90 °C under hydrogen at atmospheric pressure. The product has been characterised by microanalysis, spectroscopy (IR, 1H and 31P NMR) and X‐ray diffraction. In the solid state one hydrogen, one CO and one triphenylphosphane ligand are terminally bonded to each iridium atom, whereas four hydride ligands are bridging. All the hydrogen atoms were directly located by X‐ray analysis at an average H−Ir distance of 1.55 Å (for the terminal H) and 1.75 Å (for the μ‐H). As shown by 1H and 31P NMR spectra, two isomeric forms (1A and 1B) of the cluster are present in CD2Cl2 solution at room temperature, and they do not interconvert in the explored temperature range. However, if a solid sample of the cluster is dissolved at 188 K, only 1A is detected by NMR spectroscopy. The structure of 1B could be proposed on the basis of the T1 relaxation times of the various hydrides: it results by localised exchange of H and CO around two vertices of the tetrahedral frame. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Bridged Aminotroponiminate Complexes of Zinc
Authors: Gamer Michael T. , Roesky Peter W.
Published: May 2003

Reactions of the n‐propyl‐bridged diaminotroponimine H2{(iPr)TP} with dialkylzinc compounds in toluene lead, depending on the stoichiometric ratio, either to dimetallic singly bridged products of composition [(RZn)2{(iPr)TP}] [R = Me (1), Et (2)] or to dimetallic doubly bridged helical products of composition [Zn{(iPr)TP}]2 (3). Compound 3, which was characterised by single‐crystal diffraction methods, is the first bridged aminotroponiminate complex in which a helical structure is observed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
The Use of Conductivity Measurements for the Characterization of Cationic Palladium(II) Complexes and for the Determination of Kinetic and Thermodynamic Data in Palladium‐Catalyzed Reactions
Authors: Jutand Anny
Published: May 2003

This review illustrates how conductivity measurements are used to characterize the cationic character of aryl‐, vinyl‐, hydrido‐, and (η3‐allyl)palladium(II) complexes generated by oxidative addition of aryl and vinyl triflates, acetic/formic acid, and allylic carboxylates/carbonates, respectively, with palladium(0) complexes in DMF. These cationic palladium(II) complexes have been postulated as key intermediates in Stille, Heck, Tsuji−Trost, and Trost reactions, but most of them have never been characterized in the context of real oxidative additions, i.e., with the counteranion delivered by the reagent (triflates, carboxylates, and carbonates). The role of chloride ions has been examined and the mechanistic consequences are reported. Conductivity measurements are also used to obtain thermodynamic and kinetic data on the formation of cationic palladium(II) complexes and, consequently, to gain a deeper insight into the mechanism of palladium‐catalyzed reactions. The reversibility of oxidative additions of acetic/formic acid and allylic carboxylates/carbonates with Pd0 complexes has been established and equilibrium constants have been determined. The isomerization of cyclic trans/cis cationic (η3‐allyl)palladium(II) complexes is evidenced by a rate constant that depends on the Pd0 precursor: kinetic evidence for an SN2 mechanism that is responsible for the loss of stereoselectivity observed in catalytic reactions. Under conditions in which the oxidative additions are irreversible, the kinetics of the formation of cationic (η3‐allyl)palladium(II) complexes has been monitored by conductivity measurements for the determination of the rate constants. By comparing the rate of disappearance of Pd0, it has been shown that oxidative additions of allylic carboxylates proceed in two steps with the detection of intermediate neutral, kinetic Pd0 complexes ligated to the allylic carboxylate unit. As an example of its application, the mechanism of a Stille reaction has been investigated by conductivity measurements of an ionic by‐product in DMF. © Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003
P−B Adducts of 3,4‐Dimethyl‐1‐phosphaferrocene with Bromoboranes
Authors: Scheibitz Matthias , Bats Jan W. , Bolte Michael , Wagner Matthias
Published: May 2003

The crystalline adducts FcP−BBr3 (2) and FcP−BBr2Fc (3), which are very rare examples of P‐bonded complexes between phosphaferrocene and a main‐group metal atom, were obtained by the reaction of 3,4‐dimethyl‐1‐phosphaferrocene (FcP) with BBr3 and FcBBr2 (Fc: ferrocenyl). According to X‐ray crystallography, the Fe−P bond length in 2 is 0.085 Å shorter than in the parent phosphaferrocene. All structural changes resulting from P−B acid−base pairing follow the same qualitative trend, but are significantly larger than those occurring from the formation of transition metal complexes of phosphaferrocene. In contrast to 2, NMR spectroscopy reveals 3 to be almost completely dissociated in CDCl3 solution at room temperature. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Tungsten(VI) Complexes Derived from Calix[6]‐ and ‐[8]arenes: Oxo and Oxychloride Species
Authors: Redshaw Carl , Elsegood Mark R. J.
Published: May 2003

Treatment of p‐tert‐butylcalix[6]areneH6 (H6L) or p‐tert‐butylcalix[8]areneH8 (H8L1) with 2 equiv. of [WOCl4] in refluxing toluene affords, after workup, the complexes [(WOCl2)2LH2] (1) and [{WO(NCMe)}2L1] (2), respectively. The molecular structures of 1 and 2 have been determined and reveal conformationally constrained macrocyclic rings. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Electrochemical Study of PW12O$\rm{_{40}^{3-}}$ in Poly(ethylene glycol) Electrolyte
Authors: Zhao Feng , Gu Ningyu , Liu Shaoqin , Wang Zhenxin , Dong Shaojun
Published: May 2003

The electrochemical properties of PW12O$\rm{_{40}^{3-}}$ (abbreviated as PW12) anion in poly(ethylene glycol) (PEG) have been studied by cyclic voltammetry, complex impedance and FT‐IR spectroscopy. The PW12 anion in PEG‐LiClO4 electrolyte shows reasonable facile electrochemistry, and the diffusion coefficients of PW12 were measured with microelectrode. It is shown that ionic conductivity of polymer electrolytes based on low molecular weight PEG can be improved by the addition of PW12. The increase of conductivity is coupled with decrease of transient cross‐links density of polymer chains which is evidenced by the downshift of COC stretching mode. The phenomena are explained in view of ion‐ion and ion‐polymer interactions.
Cyclic Voltammetry and Structural Studies of Nitric Oxide Monolayers Adsorbed on Pt(111)
Authors: Casero E. , Martin‐Gago J. A. , Alonso C.
Published: May 2003

The structural analysis of the adsorption of NO monolayers on Pt(111) from solution has been explored by cyclic voltammetry (CV) and X‐ray photoelectron spectroscopy (XPS) techniques. The monolayers were formed from acid solutions saturated with NO gas as well and from nitrite solutions in sulfuric acid. Results by both techniques indicate a maximum coverage of 0.2 monolayers as well as the presence of NO molecularly adsorbed on the surface with different orientations. The voltammetric oxidation of NO gives rise to two peaks separated in the voltammogram by 50 mV. This value is in agreement with the theoretical value of 9 kJ corresponding to the difference between different adsorption sites. A mechanism for the surface mediated oxidation process from adsorbed NO to NO2 under potential control is proposed.
Natural Bioactive Material: A Preparation of Soluble Eggshell Membrane Protein
Authors: Yi Feng , Yu Jian , Guo Zhao‐Xia , Zhang Li‐Xia , Li Qiang
Published: May 2003

The proteins of eggshell membranes, an industrial waste product, are dissolved by reductive cleavage with aqueous 3‐mercaptopropionic acid and acetic acid. The soluble protein preparation is cast into a thin film, and its bioactivity is investigated by cell culture.

Photomicrograph of NIH3T3 fibroblasts cultured on SEP film for 3 days.

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Photomicrograph of NIH3T3 fibroblasts cultured on SEP film for 3 days.
Gels at Extremely Low Weight Fractions Formed by Irreversible Self‐Assembly of Proteins
Authors: Veerman Cecile , Sagis Leonard M. C. , van der Linden Erik
Published: May 2003

Food‐grade biomaterials, like β‐lactoglobulin, bovine serum albumin, and ovalbumin, can assemble into fibrils. Using the irreversible fibril formation for β‐lactoglobulin, gels can be formed even at protein concentrations of 0.07%. These fibrillar mesostructures form new structuring materials for food and pharmaceutical applications.

TEM micrograph of β‐lg at pH 2, after heating at 80 °C for 10 h and then the pH was adjusted to pH 8.

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TEM micrograph of β‐lg at pH 2, after heating at 80 °C for 10 h and then the pH was adjusted to pH 8.
Synthesis of a Polyphenol with a Mesoionic 6‐Oxo‐1,6‐dihydropyrimidin‐3‐ium‐4‐olate as Pendant Group and Its Photochemical Behavior
Authors: Tonami Hiroyuki , Uyama Hiroshi , Kobayashi Shiro , Menges Bernhard , Mittler Silvia , Theis Alexander , Ritter Helmut
Published: May 2003

This study deals with the synthesis of a polyphenol bearing photosensitive groups, and its photochemical behavior upon UV irradiation. Mesoionic 5‐(4‐hydroxybenzyl)‐6‐oxo‐1,2,3‐triphenyl‐1,6‐dihydropyrimidin‐3‐ium‐4‐olate was prepared by condensation of 4‐benzyloxybenzylmalonic acid with N,N′‐diphenylbenzamidine using dicyclohexylcarbodiimide as condensing agent, followed by deprotection of the benzyl group. The monomer was polymerized by an iron‐salen complex to give a polymer with a mesoionic 6‐oxo‐1,6‐dihydropyrimidin‐3‐ium‐4‐olate moiety as the pendant group. Spin coated polymer films were prepared and characterized. It was shown by IR spectroscopy that irradiation with UV light converted the mesoionic structure to a bis(β‐lactam) structure. Waveguide spectroscopy showed a large decrease in the film thickness without refractive index changes during irradiation.

Time development of the refractive index and the film thickness measured with p‐polarized light.

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Time development of the refractive index and the film thickness measured with p‐polarized light.
Synthesis and Characterization of Conducting Copolymers of (S)‐2‐Methylbutyl‐2‐(3‐thienyl)acetate with Pyrrole and Thiophene
Authors: Levent Anil , Toppare Levent , Cianga Ioan , Yağci Yusuf
Published: May 2003

Polymerization of methylbutyl‐2‐(3‐thienyl)acetate (MBTA) was achieved by constant current electrolysis at low temperature. Subsequently, the syntheses of block copolymers of polyMBTA were accomplished in the presence of either pyrrole or thiophene by constant potential electrolysis. Moreover, the copolymer of MBTA with thiophene was obtained with constant potential electrolysis.

The synthesis of monomer MBTA.

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The synthesis of monomer MBTA.
Synthesis and Characterization of Amphiphilic Poly(ethylene oxide)‐block‐poly(hexyl methacrylate) Copolymers
Authors: Mahajan Surbhi , Renker Sabine , Simon Peter F. W. , Gutmann Jochen S. , Jain Anurag , Gruner Sol M. , Fetters Lewis J. , Coates Geoffrey W. , Wiesner Ulrich
Published: May 2003

We describe the preparation of amphiphilic diblock copolymers made of poly(ethylene oxide) (PEO) and poly(hexyl methacrylate) (PHMA) synthesized by anionic polymerization of ethylene oxide and subsequent atom transfer radical polymerization (ATRP) of hexyl methacrylate (HMA). The first block, PEO, is prepared by anionic polymerization of ethylene oxide in tetrahydrofuran. End capping is achieved by treatment of living PEO chain ends with 2‐bromoisobutyryl bromide to yield a macroinitiator for ATRP. The second block is added by polymerization of HMA, using the PEO macroinitiator in the presence of dibromobis(triphenylphosphine) nickel(II), NiBr2(PPh3)2, as the catalyst. Kinetics studies reveal absence of termination consistent with controlled polymerization of HMA. GPC data show low polydispersities of the corresponding diblock copolymers. The microdomain structure of selected PEO‐block‐PHMA block copolymers is investigated by small angle X‐ray scattering experiments, revealing behavior expected from known diblock copolymer phase diagrams.

SAXS diffractograms of PEO‐block‐PHMA diblock copolymers with 16, 44, 68 wt.‐% PEO showing spherical (A), cylindrical (B), and lamellae (C) morphologies, respectively.

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SAXS diffractograms of PEO‐block‐PHMA diblock copolymers with 16, 44, 68 wt.‐% PEO showing spherical (A), cylindrical (B), and lamellae (C) morphologies, respectively.
Free Energy of a Non‐Gaussian Polymer Brush
Authors: Amoskov Victor M. , Pryamitsyn Victor A.
Published: May 2003

An analytical theory describing layers of polymer chains grafted to a planar surface (i.e. polymer brush) is developed. We consider a brush of chains with finite extensibility (or non‐Gaussian brush) within the framework of molecular field theory. An analytical solution for free energy of the brush and a few other brush characteristics are obtained and studied. Comparison with other known models of a brush is also made.

Chain extensibility E(x, y) for Gaussian model (dashed lines) and BCC model (solid lines) for a few chain end positions y (numbers near curves).

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Chain extensibility E(x, y) for Gaussian model (dashed lines) and BCC model (solid lines) for a few chain end positions y (numbers near curves).
Chemical Composition Distribution of Multicomponent Copolymers
Authors: Anantawaraskul Siripon , Soares João B. P. , Wood‐Adams Paula M.
Published: May 2003

The number and weight chemical composition distributions in random terpolymers were derived using a statistical approach. The solution was then generalized to comprise higher multicomponent copolymers. The analytical solution was verified with Monte Carlo simulations and by considering limiting cases. Chemical composition distributions for fractions of random terpolymers of various kinetic chain lengths were also investigated. In a similar way to the results for binary copolymers described by Stockmayer's distribution, broadening of the distribution is observed for low‐molecular‐weight chains.

Comparison of chemical composition distributions from Stockmayer (Equation (3)) and statistical approach (Equation (4)).

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Comparison of chemical composition distributions from Stockmayer (Equation (3)) and statistical approach (Equation (4)).
Free‐Radical Frontal Copolymerization: The Dependence of the Front Velocity on the Monomer Feed Composition and Reactivity Ratios
Authors: Perry Michael F. , Volpert Vladimir A. , Lewis Lydia L. , Nichols Homer A. , Pojman John A.
Published: May 2003

Frontal copolymerization is a process in which a spatially localized reaction zone propagates into a mixture of two monomers, converting them into a copolymer. In the simplest case of free‐radical copolymerization, a mixture of monomers and initiator is placed into a test tube. Reaction is initiated at one end of the tube, and a self‐sustained thermal wave, in which chemical conversion occurs, develops and propagates through the tube. We develop a mathematical model of the frontal copolymerization process and analytically determine the structure of the polymerization wave, the propagation velocity, maximum temperature, and degree of conversion of the monomers. Specifically, we examine their dependence on reactivity ratios as well as other kinetic parameters, monomer feed composition, and exothermicity of the reactions. Our analytic results are in good quantitative agreement with both direct numerical simulations of the model and experimental data, which are also presented in the paper.

Dependence of front velocity on monomer feed composition for different heat release parameters.

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Dependence of front velocity on monomer feed composition for different heat release parameters.
Polaron states and associated optical absorption in an emeraldine‐base polymer with 4n ± 1 nitrogen sites
Authors: Zhang Y. , Liu J. , Yu W. L.
Published: May 2003

Bond length and ring angle configurations of the (4n ± 1)‐polarons and the associated optical absorption coefficient α(ω) in an emeraldine‐base polymer were calculated on the basis of the Baranowski–Büttner–Voit (BBV) model. The numerical calculations show some obvious differences between the four types of polarons (P+4n+1, P–4n+1, P+4n–1, P–4n–1). The solutions of P+4n±1 (∼1.5 eV) and P–4n±1 (∼0.8 eV) match the 1.4 eV and 0.9 eV PA peaks very well. The theory also shows that through the optical absorption spectrum only one cannot distinguish the P+4n+1 and P+4n–1 (or P–4n+1 and P–4n–1) in detail.
On the mobility of delocalized and self‐trapped positronium states in ionic crystals
Authors: Bondarev I. V.
Published: May 2003

The temperature dependence of the diffusivity is studied for delocalized and self‐trapped positronium (Ps) atoms in ionic crystals. Detailed calculations taking into account low‐temperature and inelastic scattering corrections and a Ps scattering form‐factor have been performed for delocalized Ps. Low‐temperature and inelastic corrections to the delocalized Ps diffusivity are shown to be essential below several tens of K, while the form‐factor contribution is negligibly small up to thousand K. The mobility of self‐trapped Ps is analyzed within the framework of a small polaron approach. The hopping contribution to the self‐trapped Ps diffusivity is shown to be adiabatic in its physical nature. The tunnel contribution is in general not small and may turn out to be dominating even at very high temperatures.
The effects of bulk and surface fields on the phase diagram of a transverse Ising thin film
Authors: Kaneyoshi T.
Published: May 2003

The phase diagram of a transverse Ising thin film is investigated by the use of two theoretical frameworks, namely the standard mean field theory and the effective field theory. The effects of the ratio p between the bulk and surface transverse fields on the critical temperature are discussed by including the modification of surface exchange interaction. Some characteristic features are found in the phase diagrams when the ratio p increases from p = 1.0. They are enhanced for the film with thickness L smaller than 5.0. In particular, the critical ratio at which the critical temperature of the film with a finite transverse field reduces to zero, being independent of L, exhibits a linear relation when it is plotted against the modification of surface exchange interaction.
Anisotropy of optical absorption spectra of rare‐earth orthoaluminate DyAlO3
Authors: Valiev U. V. , Gruber J. B. , Rakhimov Sh. A. , Nabelkin O. A.
Published: May 2003

The polarization spectra of optical absorption for the 4f–4f transition 6H15/2 → 6F3/2 and 6H15/2 → 6F5/2 in the rare‐earth orthoaluminate DyAlO3 have been studied experimentally at the temperature T = 78 K. It has been shown that the non‐trivial character of the polarization absorption spectra anisotropy for low temperatures can be explained by a contribution of the J–J “mixing” mechanism for the excited multiplets of the ground 4f(n) configuration of the Dy3+ ion in the low‐symmetry crystalline field in the orthoaluminate structure. The results of numerical calculations of energies and wave functions of the Stark sublevels of the excited multiplets 6F3/2 and 6F5/2 are presented for the ground 4f9 configuration of the rare‐earth Dy3+ ion in the crystalline field of Cs symmetry.