bluuebunny/crossref_metadata_2025 huggingface dataset:
Allosteric enhancers for adenosine receptors
Authors: Olsson Ray A.
Published: May 2003

Agonist allosteric enhancers stabilize the adenosine‐A1 adenosine receptor‐G protein ternary complex, thereby potentiating and prolonging the action of adenosine. Because they act only on the ternary complex their action is event‐ and site‐specific. The 2‐Amino‐3‐aroyl‐4,5‐alkylthiophenes prolong conduction through the cardiac AV node and potentiate the cardioprotective effect of brief coronary occlusions, proof of principle that they could be useful drugs. However, they are unstable, are arylamines and thus have carcinogenic potential and some have antagonist activity, a possible cause of side effects. The recently described 2‐aminothiazole allosteric enhancers might avoid those drawbacks. Two kinds of quinoline derivatives have agonist allosteric enhancer activity at the A3 adenosine receptor. Drug Dev. Res. 58:493–495, 2003. © 2003 Wiley‐Liss, Inc.
Members of the acid blue 129 family as potent and selective P2Y‐receptor antagonists
Authors: Glänzel Markus , Bültmann Ralph , Starke Klaus , Frahm August Wilhelm
Published: May 2003

We previously reported a structure–activity study which identified Acid blue 129 (1‐amino‐4‐(2,4,6‐trimethylphenylamino)‐9,10‐dioxo‐9,10‐dihydroanthracene‐2‐sulfonic acid) as a highly selective antagonist at the P2Y‐receptor of the guinea pig taenia coli. In contrast to the less selective P2Y‐receptor antagonist Acid blue 25 (1‐amino‐4‐phenylamino‐9,10‐dioxo‐9,10‐dihydroanthracene‐2‐sulfonic acid) with its unsubstituted phenyl ring, Acid blue 129 does not show any effect at the P2X‐receptor of the rat vas deferens. It was hypothesized that the nonplanar orientation of the substituted phenyl ring vs. the anthraquinone core, caused by the buttressing methyl groups in 2′,6′‐position, prevents binding of Acid blue 129 to the P2X‐receptor. To prove this assumption we synthesized new compounds structurally related to Acid blue 129. The effects of all compounds were studied on contractions of the rat vas deferens elicited by α,β‐methylene ATP (α,β‐MeATP; mediated by P2X‐receptors) and relaxations of the carbachol‐precontracted guinea pig taenia coli elicited by adenosine 5′‐O‐(2‐thiodiphosphate) (ADPβS; mediated by P2Y‐receptors). All compounds were more or less P2Y‐ vs. P2X‐selective. In contrast to our assumption, it is the 4′‐methyl group of Acid blue 129 and of its new analog MG 32 (1‐amino‐4‐(4‐methylphenylamino)‐9,10‐dioxo‐9,10‐dihydroanthracene‐2‐sulfonic acid) which completely prevents binding to the P2X‐receptor up to 100 μM antagonist concentration, whereas the P2X‐receptor is blocked by related compounds lacking the 4′‐methyl group. Acid blue 129 and MG 32 were the most interesting compounds. Both turned out to be potent P2Y‐receptor antagonists with IC50‐values of approximately 3 μM. They are highly selective vs. both P2X‐receptor and non‐P2‐receptor effects. Drug Dev. Res. 59:64–71, 2003. © 2003 Wiley‐Liss, Inc.
The immunodominant epitope of lipocalin allergen Bos d 2 is suboptimal for human T cells
Authors: Kinnunen Tuure , Buhot Cecile , Närvänen Ale , Rytkönen‐Nissinen Marja , Saarelainen Soili , Pouvelle‐Moratille Sandra , Rautiainen Jaakko , Taivainen Antti , Maillère Bernard , Mäntyjärvi Rauno , Virtanen Tuomas
Published: May 2003

We have proposed earlier that the poor capacity of the lipocalin allergen Bos d 2 to stimulate highly allergic subjects' peripheral blood mononuclear cells could be ascribed to endogenouslipocalins and could be related to the allergenic potential of the molecule. Here, we have characterized the proliferative and cytokine responses of human T cell clones against the immunodominant epitope of Bos d 2. We observed, for clone F1‐9, that a substitution of aspartic acid for asparagine in the core region of the epitope increased the stimulatory capacity of the peptide about 100‐foldin comparison with the natural peptide. For clone K3‐2, from a different patient, the substitution of lysine for glutamine or isoleucine for leucine in the core region resulted in about 30‐fold and10‐fold increases in the stimulatory capacity of the peptides, respectively. The clones also recognized self‐protein‐derived peptides but not the peptides derived from other lipocalins. We suggest that the poor recognition of the immunodominant epitope of Bos d 2 can be a factor accounting for Bos d 2‐allergic subjects' weak cellular responses. Suboptimal recognition of self and allergen epitopesby T cells may be of significance for the allergenicity of proteins.
Prevention of allergen‐specific IgE production and suppression of an established Th2‐type response by immunization with DNA encoding hypoallergenic allergen derivatives of Bet v 1, the major birch‐pollen allergen
Authors: Hochreiter Romana , Stepanoska Tatjana , Ferreira Fatima , Valenta Rudolf , Vrtala Susanne , Thalhamer Josef , Hartl Arnulf
Published: May 2003

In atopic patients, programming towards a preferential Th2 immunity leads to IgE antibody production and cellular Th2 immunity against otherwise harmless antigens. We report the development ofprophylactic and therapeutic DNA vaccines for the major birch‐pollen allergen, Bet v 1. We constructed three DNA vaccines, coding for the complete cDNA, coding for two hypoallergenic fragments or coding for a hypoallergenic Bet v 1 mutant. The protective effect was studied in mice pretreated by intradermal DNA injections, then sensitized with Bet v 1 protein. Mice pretreated with any of the three Bet v 1‐specific DNA vaccines were protected against allergic sensitization to Bet v 1. Protection was characterized by a lack of Bet v 1‐specific IgE production, a lack of basophil activation and an enhanced IFN‐γ expression. DNA vaccines with wild‐type Bet v 1 induced strong Bet v 1‐specific antibody responses whereas DNA vaccines with hypoallergenic Bet v 1 derivatives induced no (fragments) or only transient (mutant) Bet v 1‐specific antibody responses. A therapeutic approach with the fragment‐DNA vaccine reduced IgE production and stimulated a sustained Th1 cytokine milieu. Our results demonstrate that DNA vaccines with hypoallergenic forms of the allergen specifically protect against sensitization and suppress established Th2‐type responses. This concept may be applied for the development of safe and specific DNA vaccines for the prophylaxis and therapy of allergic diseases.
Human cytomegalovirus impairs dendritic cell function: a novel mechanism of human cytomegalovirus immune escape
Authors: Beck Kerstin , Meyer‐König Ursula , Weidmann Manfred , Nern Christian , Hufert Frank T.
Published: May 2003

Human cytomegalovirus (HCMV) employs multiple mechanisms to evade the immune system and succeeds to persist lifelong in the host. Human dendritic cells (DC) are the main antigen‐presenting cells and play the key role in inducing and maintaining immune responses. Here, we studied the interaction of HCMV with DC. We found that DC, irrespectively of their stage of maturation, were fully permissive for HCMV when endothelial cell‐adapted HCMV strains were applied. When fibroblast‐adapted strains were used, viral replication was abrogated at the level of immediate early (IE) and/or early (E) gene expression. Irrespective of the HCMV strain used, infection of DC prevented the signal delivery essential for T cell activation in a multistep manner. Furthermore, we observed an altered expression of adhesion molecules. This might contribute to an impairment of DC migration. Our data indicate that a soluble factor induced by IE and/or E genes is involved in these processes. The impairment of DC function upon HCMV infection may contribute to virus‐mediated immunosuppression and help the virus to establish persistence in the host.
The generalized endotoxic principle
Authors: Seydel Ulrich , Hawkins Lynn , Schromm Andra B. , Heine Holger , Scheel Olaf , Koch Michel H. J. , Brandenburg Klaus
Published: May 2003

Bacterial lipopolysaccharides (endotoxins, LPS) belong to the most potent immunostimulators in mammals. The endotoxic principle of LPS is located in its lipid A moiety, which for Escherichia coli‐type LPS consists of a hexaacylated diphosphoryl diglucosamine backbone. This lipid A adopts a cubic inverted aggregate structure from which a conical shape of the molecule can be deduced, whereas the tetraacyl lipid A precursor IVa adopts a cylindrical shape and is endotoxically inactive, but antagonizes active LPS. We hypothesize that non‐lipid A amphiphiles with similar physicochemical properties of amphiphilicity, charge, and shape, might mimic the respective lipid A. To test this hypothesis, phospholipid‐like amphiphiles with six acyl chains attached to a bisphosphorylated serine‐like backbone of varying length replacing the diglucosamine backbone were synthesized. The compound with a short backbone fulfills all criteria of an endotoxic agonist, and that with longbackbone fulfills those of an antagonist. This holds true for the human as well as for the murine system. Interestingly, these compounds are inactive in the Limulus amebocyte lysate test which is specific for LPS diglucosamine backbone. These results define a general endotoxic principle and, furthermore, provide new insights into an understanding of early steps of endotoxin action.
Skin‐versus gut‐skewed homing receptor expression and intrinsic CCR4 expression on human peripheral blood CD4+CD25+ suppressor T cells
Authors: Iellem Andrea , Colantonio Lucia , D'Ambrosio Daniele
Published: May 2003

In humans and rodents a population of naturally occurring CD4+CD25+ T cells are suppressor T (CD25+ Ts) cells, which are considered to maintain peripheral immunological tolerance. Recently, we have described a unique chemotactic response profile for human CD25+ Ts cells, but their homing potential remains poorly defined. Here, we document a heterogeneous homing potential of human peripheral blood CD25+ Ts cells consistent with their ability to mediate immunosuppression at distinct locations. Surprisingly, CD25+Ts cells are depleted of gut‐homing integrin α4+β7+ T cells, while being enriched in skin‐homing cutaneous lymphocyte antigen (CLA)+ T cells. These findings document heterogeneous homing potential of peripheral blood‐borne CD25+ Ts cells with marked skewing for skin‐ versus gut‐homing. Expression of CCR4 associates with both CD25 and CLA cell surface markers, being highest on CD4+CLA+CD25+ T cells. Importantly, CD4+CD25+ Ts cells isolated from human cord blood lack expressionof CLA while expressing CCR4, suggesting intrinsic expression of CCR4 on CD25+ Ts cells. These observations indicate that the increased expression of CCR4, which is proposed to guide CD25+ Ts cells to DC, is an intrinsic feature of CD25+ Ts cells.
Ganglioside GD3 expression on target cells can modulate NK cell cytotoxicity via siglec‐7‐dependent and ‐independent mechanisms
Authors: Nicoll Gavin , Avril Tony , Lock Kevin , Furukawa Koichi , Bovin Nicolai , Crocker Paul R.
Published: May 2003

Siglec‐7 is a sialic acid binding receptor with inhibitory potential, expressed on human NK cells and monocytes. It has an unusual binding preference for α2,8‐linked disialic acids, such as those displayed by ganglioside GD3. Here we have investigated whether siglec‐7‐GD3 interactions are able to modulate NK cell cytotoxicity. Using synthetic polyacrylamide glycoprobes, siglec‐7 was found to be masked at the NK cell surface but it could be unmasked by sialidase treatment of NK cells. GD3 synthase‐transfected P815 target cells expressed high levels of GD3 and bound strongly to recombinant siglec‐7‐Fc protein. Surprisingly, GD3 synthase‐transfected P815 cells were killed more effectively by untreated cells in a siglec‐7‐independent manner. However, following sialidase treatment of NK cells, a siglec‐7‐dependent inhibition of killing was observed. These findings have important implications for NK cell cytotoxicity against tumor cells like melanoma that express high levels of GD3 ganglioside.
Virus infection expands a biased subset of T cells that bind tetrameric class I peptide complexes
Authors: Coles Richard M. , Jones Claerwen M. , Brooks Andrew G. , Cameron Paul U. , Heath William R. , Carbone Francis R.
Published: May 2003

We have used a TCR β‐chain transgenic mouse to examine the relationship between the ability of a T cell to bind soluble class I‐peptide complexes and its response to antigenic stimulation in vivo. T cells from gBT‐I.3β TCR β‐chain transgenic mice preferentially carried TCR α‐chains bearing the same Vα2 V region as found in the parent receptor specific for an immunodominant HSV‐1 gB‐peptide. Furthermore, CD8+ T cells from these mice bound Kb‐gB tetrameric complexes with relatively high frequency, and most of these cells contained a Vα2 TCR α‐chain. Detailed sequence analysis of the tetramer‐binding peripheral T cells showed that this was a heterogenous population expressing TCR with only partial sequence similarity to the parent receptor, which took the form of preferential inclusion of the parental Jα16 element. Infection with HSV‐1, however, selected a subset of tetramer‐positive T cells. This was based on the emergence of a co‐dominant Jα usage and selection of a restricted CDR3α length. Therefore, the ability to bind soluble MHC‐peptide complexes does not always correlate with the ability of a T cell to respond to its cognate antigen after in vivo stimulation.
Lymphotoxin β receptor‐Ig fusion protein treatment blocks actively induced, but not adoptively transferred, uveitis in Lewis rats
Authors: Shao Hui , Fu Yangxin , Song Lei , Sun Sheher , Kaplan Herry J. , Sun Deming
Published: May 2003

Previous studies have shown that treatment of rodents with a lymphotoxin (LT) β receptor‐Ig fusion protein (LTβR‐Ig), which binds to both LT and LIGHT, prevents the development of autoimmune diseases, but the mechanism involved is unclear. To explore the potential role of LT or LIGHT in the pathogenesis of autoimmune uveitis, uveitis was induced in Lewis rats either by immunization with an uveitogenic peptide, R16, derived from the interphotoreceptor retinoid‐binding protein, or by adoptive transfer of R16‐specific T cells. Interestingly, LTβR‐Ig treatment completely prevented actively induced uveitis, but not the adoptively transferred disease. We also show that LTβR‐Ig‐treated R16‐injected rats had a significantly decreased T cell response to R16 and that herpesvirus entry mediator (HVEM)‐Ig, a fusion protein that blocks LIGHT, also inhibited disease development. Our results suggest that LT or LIGHT plays a critical role in the induction, rather than the effector, phase of the disease.
Vaccination with myelin oligodendrocyte glycoprotein adsorbed to alum effectively protects DBA/1 mice from experimental autoimmune encephalomyelitis
Authors: Wållberg Maja , Wefer Judit , Harris Robert A.
Published: May 2003

To prevent an organism from developing autoimmunity the body limits the number of autoreactive cells through thymic negative selection and regulates their activity through induction of suppressor T cells. Development of antigen‐specific therapies provides an interesting opportunity to imitate the body's own, often effective, method of protection. Our study demonstrates that DBA/1 mice could be protected from experimental autoimmune encephalomyelitis induced through injection of recombinant myelin oligodendrocyte glycoprotein (rMOG) when they were previously immunized intraperitoneally with rMOG adsorbed to aluminium hydroxide. This protection was associated with a decreased IFN‐γ production by rMOG‐specific cells, but not a decreased proliferative response. Protection was long lasting, indicating that MOG‐alum vaccination might be developed as a prophylactic therapy in multiple sclerosis.
Th2 cells shape the differentiation of developing T cell responses during interactions with dendritic cells in vivo
Authors: Schipf Alexander , Heilmann Annette , Boue Laetitia , Mossmann Horst , Brocker Thomas , Röcken Martin
Published: May 2003

During priming, naive CD4+ Th cells differentiate into cells that produce either IFN‐γ or IL‐4. Even though the cascade of pathways that induces IL‐4‐producing Th2 cells has been determined in vitro, the signals promoting Th2 differentiation under physiological conditions remain enigmatic, especially the natural role of the single most important Th2‐inducing signal,IL‐4. Using Th2 and naive Th cells, each expressing a distinct transgenic TCR, here we show that Th2 cells migrate with the same dynamics as naive Th cells in draining lymph nodes and bind to the same DC, when driven by antigen in complete Freund's adjuvant (CFA). Th2‐cell‐derived IL‐4 deviates CFA‐induced Th1 development toward a Th2 phenotype, if both cell populations co‐localize in the same T cell area, and are activated simultaneously. Thus, intranodal Th2 cells directly influence Th cell differentiation in vivo, but only under restricted conditions. These findings have implications for the design of cytokine‐based therapies and explain the spreading of Th2 responses to multiple aeroallergens in allergic asthma, where naive Th and Th2 cells co‐localize in lung‐draining lymph nodes.
Instruction of naive CD4+ T cells by polarized CD4+ T cells within dendritic cell clusters
Authors: Creusot Rémi J. , Biswas Jason S. , Thomsen Lindy L. , Tite John P. , Mitchison N. Avrion , Chain Benjamin M.
Published: May 2003

Cooperation between CD4+ T cells can enhance the response and modulate the cytokine profile, and defining these parameters has become a major issue for multivalent‐vaccine strategies.We explored cooperation using adoptive transfer of two populations of TCR transgenic T cells of different specificity. One was transferred without prior activation, whereas the second was activatedfor five days by antigen stimulation under polarizing culture conditions. Both populations were transferred into a single adoptive host and then primed by particle‐mediated DNA delivery. Polarized Th1 cells (inducers) raised the frequency of IFN‐γ+ cells within a naive (target) population, whereas Th2 inducers raised the frequency of IL‐4+ and reduced that of IL‐2+ cells. These effects were obtained when the genes for both antigens were on the same particle, favoring presentation by the same dendritic cell, but not when on different particles delivered to different dendritic cells. Autonomy of DC clusters allows linked sets of antigens (e.g. from a single pathogen) to maintain cytokine bias, but allows other independent responses, each with their own set of autonomous clusters.
Amino acid composition of α1/α2 domains and cytoplasmic tail of MHC class I molecules determine their susceptibility to human cytomegalovirus US11‐mediated down‐regulation
Authors: Barel Martine T. , Pizzato Nathalie , van Leeuwen Daphne , Bouteiller Philippe Le , Wiertz Emmanuel J. H. J. , Lenfant Francoise
Published: May 2003

During co‐evolution with its host, human cytomegalovirus has acquired multiple defense mechanisms to escape from immune recognition. In this study, we focused on US11, which binds to MHC class I heavy chains and mediates their dislocation to the cytosol and subsequent degradation by proteasomes. To examine which domains of class I heavy chains are involved in this process, we constructedchimeric HLA molecules of US11‐sensitive and ‐insensitive class I molecules (HLA‐A2 and HLA‐G, respectively). Pulse‐chase experiments were performed to evaluate protein stability and interactions between class I heavy chains and US11. Flow cytometry was employed to assess the effect of US11 on surface expression of the different chimeras. Our results indicate that the α1 and α2 domains of HLA molecules are important for the affinity of US11 association. However, the degradation efficiency seems to rely mostly on cytosolic tail residues. We found that the nonclassical HLA‐G molecule is insensitive to US11‐mediated degradation solely because it lacks essential tail residues. A deletion of the last two tail residues in full‐length MHC class I molecules already caused a severe reduction in degradation efficiency. Altogether, our data provide new insights into the mechanism by which US11 down‐regulates MHC class I molecules.
Respiratory syncytial virus‐induced CCL5/RANTES contributes to exacerbation of allergic airway inflammation
Authors: John Alison E. , Berlin Aaron A. , Lukacs Nicholas W.
Published: May 2003

Severe respiratory syncytial virus (RSV) infection has a significant impact on airway function and may induce or exacerbate the response to a subsequent allergic challenge. In a murine model combining early RSV infection with later cockroach allergen (CRA) challenge, we examined the role of RSV‐induced CCL5/RANTES production on allergic airway responses. RSV infection increased CCL5 mRNAand protein levels, peaking at days 8 and 12, respectively. Administration of CCL5 antiserum during days 0–14 of the RSV infection did not significantly alter viral protein expression when comparedto mice treated with control serum. In mice receiving the combined RSV‐allergen challenge, lungs collected on day 22 exhibited significantly increased numbers of CD4‐ and CD8‐positive T cells. Thisincrease in T cell numbers was not observed in mice receiving α‐CCL5. On day 43, peribronchial eosinophilia and leukotriene levels were increased in RSV‐allergen mice. Pretreatment with CCL5 antiserum resulted in decreased recruitment of inflammatory cells to bronchoalveolar and peribronchial regions of the lungs and these reductions were associated with a reduction in both T cell recruitment into the bronchoalveolar space, leukotriene release and chemokine generation. Thus, CCL5 released during RSV infection has a significant effect on the inflammatory response to subsequent allergic airway challenges.
T cell receptor CDR3 loop length repertoire is determined primarily by features of the V(D)J recombination reaction
Authors: Hughes Maureen M. , Yassai Maryam , Sedy John R. , Wehrly Tara D. , Huang Ching‐Yu , Kanagawa Osami , Gorski Jack , Sleckman Barry P.
Published: May 2003

The third complementarity‐determining region (CDR) of the TCR α and β chains forms loops that engage amino acid residues of peptides complexed with MHC. This interaction is central to the specific discrimination of antigenic‐peptide–MHC complexes by the TCR. The TCRβ chain CDR3 loop is encoded by the Dβ gene segment and flanking portions of the Vβ and Jβ gene segments. The joining of these gene segments is imprecise, leading to significant variability in the TCRβ chain CDR3 loop length and amino acid composition. In marked contrast to other pairing antigen‐receptor chains, the TCR β and α chain CDR3 loop size distributions are relatively narrow and closely matched. Thus, pairing of TCR α and β chains with relatively similar CDR3 loop sizes may be important for generating a functional repertoire of α β TCR. Here we show that the TCRβ chain CDR3 loop size distribution is minimally impacted by TCRβ chain or α β TCR selection during thymocyte development. Rather, this distribution is determined primarily at the level of variable‐region gene assembly, and is critically dependent on unique features of the V(D)J recombination reaction that ensure Dβ gene segment utilization.
Mini‐review The role of interleukin‐12 in human infectious diseases: only a faint signature
Authors: Fieschi Claire , Casanova Jean‐Laurent
Published: May 2003

IL‐12 is the signature IFN‐γ‐inducing cytokine and, as such, is thought to be crucial for protective immunity against intracellular microorganisms. This concept is supported by results from experimental infections of knockout mice lacking IL‐12 or the IL‐12 receptor. The description of human patients with inherited IL‐12 or IL‐12‐receptor deficiency challenges this view. Indeed, in natural conditions of infection and immunity — the hallmark of the human model — IL‐12 was found to be redundant in defense against intracellular microorganisms other than Mycobacteria and Salmonella. More surprisingly, IL‐12 was recently found to be redundant even in defense against primary intection by Mycobacteria and Salmonella in many patients, and against secondary infection by Mycobacteria but not Salmonella in most patients.
First (Peroxo)vanadium(V) Complex with Heteroligand Formed in Reaction System − Synthesis, Structure and Reactivity of K[VO(O2)(omeida)]·H2O {omeida = N‐[2‐(2‐oxomorpholine‐4‐yl)ethyl]iminodiacetato(2−)}
Authors: Sivák Michal , Mad’arová Mariana , Tatiersky Jozef , Marek Jaromír
Published: May 2003

The crystalline peroxo complex of vanadium(V), K[VO(O2)(omeida)]·H2O, where omeida is a δ‐lactone derivative, N‐[2‐(2‐oxomorpholine‐4‐yl)ethyl]iminodiacetate(2−), has been obtained by reaction of vanadate with H2O2 and N‐(2‐hydroxyethyl)ethylenediaminetriacetic acid (HEDTA) in acidic aqueous solution at pH = 3 and 278 K. X‐ray analysis revealed a distorted pentagonal‐bipyramidal coordination around the vanadium atom, with a typical cis arrangement of oxo and peroxo ligands in apical and equatorial positions, respectively. Two amino nitrogen atoms of the tetradentate omeida(2−)‐N1,N2,O1,O2 ligand occupy the neighbouring equatorial positions of the pentagonal plane, and two oxygen atoms of carboxymethyl groups bound to the same N1 nitrogen atom are in equatorial and apical positions. The six‐membered lactone ring in omeida was formed in the reaction solution from carboxy and hydroxy groups not involved in coordination with the vanadium atom. The 51V NMR spectra of K[VO(O2)(omeida)]·H2O, and of peroxovanadate/HEDTA/H2O and vanadate/HEDTA/H2O solutions, as well as the 1H NMR spectrum of HEDTA, proved that lactone ring closure proceeds only in peroxovanadate but not vanadate solutions. Spectroscopic investigation of the oxygen transfer reaction from the peroxo ligand in [VO(O2)(omeida)]− to the thiolato sulfur atom in [Co(en)2{S(CH2)2NH2}]2+ or [Co(en)2(cyst)]+, and of the oxidation of N‐acetyl‐L‐cysteine by K[VO(O2)(omeida)]·H2O, revealed much more complicated reaction mechanisms than those of other (amino‐polycarboxylato)monoperoxo complexes of vanadium(V). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Extended X‐ray Absorption Fine Structure Study of Copper(I) and Copper(II) Complexes in Atom Transfer Radical Polymerization
Authors: Pintauer Tomislav , Reinöhl Ulrich , Feth Martin , Bertagnolli Helmut , Matyjaszewski Krzysztof
Published: May 2003

Extended X‐ray Absorption Fine Structure (EXAFS) spectroscopy has been used to investigate structural features of CuIBr and CuIIBr2 complexes with dNbpy, PMDETA, Me6TREN, tNtpy, and Me4CYCLAM in various solvents {dNbpy = 4,4′‐bis(5‐nonyl)‐2,2′‐bipyridine, PMDETA = N,N,N′,N′′,N′′‐pentamethyldiethylenetriamine, Me6TREN = tris[2‐(dimethylamino)ethyl]amine, tNtpy = 4,4′,4′′‐tris(5‐nonyl)‐2,2′:6′,2′′‐terpyridine, Me4CYCLAM = 1,4,8,11‐tetramethyl‐1,4,8,11‐tetraazacyclotetradecane}. The structures of the CuI and CuII complexes were found to depend on the solvent polarity and the number of nitrogen atoms in the ligand. Generally, in non‐polar media and with monomers typically used in ATRP, CuI complexes preferred a tetracoordinate geometry, and were either ionic as observed in [CuI(dNbpy)2]+[CuIBr2]− (CuI−NAV = 2.00 Å, CuI−BrAV = 2.25 Å) and [CuI(Me4CYCLAM)]+[CuIBr2]− (CuI−NAV = 2.06 Å, CuI−BrAV = 2.23 Å), or neutral as in [CuI(PMDETA)Br] (CuI−NAV = 2.12 Å, CuI−BrAV = 2.33 Å), and [CuI(tNtpy)Br] (CuI−NAV = 2.03 Å, CuI−BrAV = 2.29 Å). The EXAFS analysis of CuIIBr2 complexes indicated a preference for a coordination number of five, such as in [CuII(dNbpy)2Br]+[Br]− (CuII−NAV = 2.03 Å, CuII−BrAV = 2.43 Å), [CuII(PMDETA)Br2] (CuII−NAV = 2.03 Å, CuII−Br1,AV = 2.44 Å, CuII−Br2,AV = 2.64 Å) and [CuII(Me6TREN)Br]+[Br]− (CuII−NAV = 2.09 Å, CuII‐BrAV = 2.39 Å), with the exception of the neutral tetracoordinate [CuII(dNbpy)Br2] (CuII−NAV = 2.02 Å, CuII−BrAV = 2.36 Å), which has been observed in non‐polar media. Additionally, polar media were found to favor bromide dissociation in [CuII(Me6TREN)Br]+[Br]− and [CuII(PMDETA)Br2], as indicated by a decrease in the Br and Cu coordination numbers at the Cu‐ and Br‐K‐edges, respectively. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Probing the Nature of the CoIIIIon in Cobalamins − Spectroscopic and Structural Investigations of the Reactions of Aquacobalamin (Vitamin B12a) with Ambident Nucleophiles
Authors: Perry Christopher B. , Fernandes Manuel A. , Kenneth L. Brown  , Zou Xiang , Valente Edward J. , Marques Helder M.
Published: May 2003

The rate of substitution of the H2O β‐ligand in aquacobalamin (vitamin B12a) is surprisingly fast for CoIII. This may arise as a result of transfer of electron density to CoIIIby the corrin, conferring on the metal atom a softer and more labile character, and would require electronic communication between the equatorial ligand and the axial coordination sites of the metal atom. We have substituted H2O in B12awith the ambidentate nucleophiles SCN−, SeCN−, NO2−and S2O32−, examined the UV/Vis spectra of the resultant complexes, crystallised them, and determined their structures by X‐ray diffraction methods. The UV/Vis spectra of these complexes, as well as those of H2OCbl+, SO3Cbl−and MeCbl, were fitted by Gaussian functions. The principal bands move to lower energy in response to an increase in donation of electron density from the axial ligand, demonstrating direct electronic communication between the axial and the equatorial ligands. In the solid state, the thiocyanato ligand in SCNCbl is coordinated through N, although13C NMR spectroscopy shows that the complex exists as a mixture of two linkage isomers in solution. SeCN−, NO2−and S2O32−are coordinated through the softer available donor in each case (Se, N and S, respectively). There is a regular ground‐statetranseffect such that as the donor power of the β‐ligand increases, thetransCo−Naxbond length increases. A survey of the structures available in the CSD shows that this preference for the softer donor atom in ambidentate nucleophiles is not unusual in CoIIIcomplexes. The Co−N bond length in SCNCbl is marginally long for coordination to CoIII, but the axial bond lengths of the other complexes are as expected. Hence, whereas the corrin macrocycle clearly imparts lability on CoIII, presumably by transfer of electron density onto the metal atom, this is insufficient to have a major effect on the ground‐state structures of its complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Surface Organometallic Chemistry on Oxides: The First Well‐Defined Selenium(IV) Derivative Grafted onto Silica
Authors: Provendier Hélène , Santini Catherine C. , Basset Jean‐Marie , Carmona Laurent
Published: May 2003

Treatment of (EtO)2SeO with Aerosil silica dehydroxylated at 500 °C results in the formation of a unique surface derivative [≡SiO−Se(O)OEt] (1), which has been fully characterized by elemental analysis, IR, labelling reaction and solid‐state NMR spectroscopy. This is the first example of a silica‐supported selenium(IV) derivative. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
New Alkali Metal Boratabenzenes: Structures of K([18]‐Crown‐6)(C5H5BMe), of the Tetrahydropyran Solvate K(3,5‐Me2C5H3B−NMe2)(THP)2, and of Two THF Solvates of K[3,5‐Me2C5H3B−N(SiMe3)2]
Authors: Zheng Xiaolai , Herberich Gerhard E.
Published: May 2003

The potassium salt K(C5H5BMe) (8) can be obtained from 2‐(Me3Sn)C5H5BMe (7)/KOtBu in toluene in essentially quantitative yield. Metalation of 1‐(dimethylamino)‐3‐methylene‐1,2,3,6‐tetrahydroborinine (9) with MN(SiMe3)2 (M = Na, K) in toluene afforded the unsolvated salts M(3,5‐Me2C5H3B−NMe2) (M = Na: 11; M = K: 12). Morpholino derivatives M(3,5‐Me2C5H3B−NC4H8O) (M = Li: 17; M = Na: 18) and the potassium salt K[3,5‐Me2C5H3B−N(SiMe3)2] (19) were obtained similarly. The unsolvated salts are highly air‐ and water‐sensitive, colorless powders. Crystallization with the help of auxiliary Lewis bases provided crystalline solvates K([18]‐crown‐6)(C5H5BMe) (20), K(THP)2(3,5‐Me2C5H3B−NMe2) (21), and the concomitant pseudopolymorphs K[3,5‐Me2C5H3B−N(SiMe3)2](THF)4/3 (α‐22) and K[3,5‐Me2C5H3B−N(SiMe3)2](THF)3/2 (β‐22), which were characterized structurally. The structures of α‐22 (space group C2/c) and β‐22 (space group 6122) display novel chain forms, which have no precedents in boratabenzene and cyclopentadienide chemistry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
The First Mononuclear η2‐C60 Complex of Osmium: Synthesis and X‐ray Crystal Structure of [(η2‐C60)Os(CO)(tBuNC)(PPh3)2]
Authors: Usatov Alexander V. , Martynova Ekaterina V. , Neretin Ivan S. , Slovokhotov Yuri L. , Peregudov Alexander S. , Novikov Yurii N.
Published: May 2003

The interaction of C60 fullerene with the cis‐dihydride osmium complex [OsH2(CO)(PPh3)3] (I) in the presence of tBuNC gives a novel metal complex [(η2‐C60)Os(CO)‐(tBuNC)(PPh3)2] (II) as the first mononuclear osmium complex with an η2‐coordinated fullerene ligand. Complex II was isolated and characterized by elemental analysis, UV, IR, 1H and 31P NMR spectroscopy. An X‐ray diffraction study of II as its dichlorobenzene solvate revealed a distorted trigonal bipyramidal coordination of the Os atom, with a 6/6 bond of C60 and two PPh3 ligands in the equatorial plane and CO and tBuNC as axial ligands. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Assembly of Seven Nickel(II) Metals by Chiral, Salen‐Type Ligands with µ3‐OH Bridges
Authors: Xu Xuan , Gou Shaohua , Huang Wei , Ma Yonglin , Li Yizhi
Published: May 2003

A chiral heptanuclear nickel(II) complex [NiII(NiII2L)3(μ3‐OH)2]·3H2O [H4L = (2R,3R)‐1,4‐bis(3,5‐di‐tert‐butylsalicylideneamino)‐2,3‐butanediol], containing two μ3‐OH bridges, has been prepared and structurally characterized; its thermal and magnetic properties were investigated. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Modulation of the Prototropic Exchange Rate at the Water Molecule Coordinated to a GdIII Ion
Authors: Aime Silvio , Gianolio Eliana , Barge Alessandro , Kostakis Dimitrios , Plakatouras Ioannis C. , Hadjiliadis Nick
Published: May 2003

The aim of this work is to assess whether it is possible to control the rate of the prototropic exchange in a class of DTPA bis‐amide GdIII complexes. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Cover Picture: Tris(pyrazolyl)methanesulfonates: More Than Just Analogues of Tris(pyrazolyl)borate Ligands; N,N,N‐, N,N,O‐, and Other Coordination Modes (Eur. J. Inorg. Chem. 11/2003)
Authors: Kläui Wolfgang , Berghahn Michael , Frank Walter , Reiß Guido J. , Schönherr Thomas , Rheinwald Gerd , Lang Heinrich
Published: May 2003

The cover picture shows two isomers of a carbonylcopper(I) complex of the new ligand tris(pyrazolyl)methanesulfonate (Tpms). This new class of ligands contains three nitrogen donor atoms and in addition a sulfonate group which makes the ligands more hydrophilic. The sulfonate group can act as a competing donor centre. Therefore Tpms ligands are ambidentate ligands, that can adapt their coordination modes according to the electronic preferences of the metal centre. In solution, e.g., carbonylcopper(I) and zinc halide complexes show an equilibrium between the N,N,N‐ and N,N,O‐coordination mode. Synthesis, characterization and the dynamic stereochemistry of Tpms and TpmstBu complexes are presented in the article by W. Kläui et al. on p. 2059 ff. We thank B. Kugel and P. Kunz for their help with the cover picture.
UV‐Visible Spectroelectrochemical Detection of Side‐Reactions in the Hexacyanoferrate(III)/(II) Electrode Process
Authors: Heras Aránzazu , Colina Alvaro , Ruiz Virginia , López‐Palacios Jesús
Published: May 2003

Hexacyanoferrate(III)/(II) system has been studied by UV‐visible long‐pathway spectroelectrochemistry. Three different methodologies, based on potentiodynamic techniques, have been successfully used in the thermodynamic characterization of the system. Formation of soluble Prussian Blue has been detected during the electrode process. The values of the formal potential (E0′=0.200 V) and the electron stoichiometry of this side‐reaction (n=0.5) have been obtained.
Electrochemical Codeposition of Platinum and Molybdenum Oxides: Formation of Composite Films with Distinct Electrocatalytic Activity for Hydrogen Peroxide Detection
Authors: Kosminsky Luis , Matos Renato Camargo , Tabacniks Manfredo H. , Bertotti Mauro
Published: May 2003

The electrochemical properties of gold electrode surfaces modified by molybdenum oxide films intercalated with platinum microparticles have been described. The incorporation of Pt microparticles at the oxide film was characterized by PIXE (particle induced X‐ray emission) spectroscopy. The modified electrode showed electrochemical activity at around −0.5 V in 50 mmol L−1 Na2SO4 supporting electrolyte (pH 3), corresponding to the reduction of protons at platinum sites and further transfer of hydrogen atoms to form reduced molybdenum oxides (bronzes). At 0.1 V, the MoO3 / Pt electrode showed a better performance for hydrogen peroxide oxidation than on platinized gold electrodes. The solution pH has a marked effect on the voltammetric profile and best responses for hydrogen peroxide were obtained at the 5.0 to 6.0 pH range. The activation of the electrode by polarization at negative potentials was also studied and a mechanism by which more platinum sites are available as a consequence of this process was proposed. Calibration plots for hydrogen peroxide were highly linear (r=0.9989) in the 0.2 to 1.6 mmol L−1 concentration range, with a relative standard deviation (RSD)<1%.
Fabrication of Poly(allylamine)ferrocene Monolayer Based on Electrostatic Interaction and Its Electrocatalytic Oxidation of Ascorbic Acid
Authors: Zhang Suxia , Fu Yaqin , Sun Changqing
Published: May 2003

A poly(allylamine)ferrocene monolayer was built on the surface of gold electrode modified with negatively charged alkanethiol based on electrostatic interaction. The electrochemical behavior of the modified electrode was characterized by cyclic voltammetry in detail. The modified electrode was shown to exhibit excellent electrocatalytic response to the oxidation of ascorbic acid. The anodic overpotential was reduced by about 170 mV compared with that obtained at a bare gold electrode. The modified electrode possesses several attractive features, such as simple preparation, fast response and good chemical and mechanical stability.
Studies on Binary Blends of Poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) and Natural Polyphenol Catechin: Specific Interactions and Thermal Properties
Authors: Zhu Bo , Li Jianchun , He Yong , Inoue Yoshio
Published: May 2003

The existence of a specific intermolecular hydrogen‐bonding interaction between poly(3‐hydroxybutyrate‐co‐3‐hydroxyhexanoate) [P(3HB‐co‐3HH)] and (+)‐catechin in their blends was demonstrated by Fourier‐transform infrared spectroscopy (FT‐IR). It was found that the experimentally estimated fraction of hydrogen‐bonded carbonyl groups was much lower than the theoretically predicted maximum fraction. Only one glass transition temperature (Tg) occurred in the blends with the compositions detected by differential scanning calorimetry (DSC), being further confirmed by the results of dynamic mechanical thermal analysis (DMTA). The decrease of the melting point (Tm) and the increase of the glass transition temperature of the blends observed by the DSC measurements also suggested the existence of a strong intermolecular interaction. It was interesting to note that, as a low‐molecular‐weight compound, catechin showed a glass transition, which arises from strong self‐association. As expected, the crystalline structure of P(3HB‐co‐3HH) in the blends showed no change, but the crystallinity of the copolymer component in the blends, calculated by wide‐angle X‐ray diffraction, decreased with the increase of catechin weight content. Investigated by tensile experiments, the maximum strength and modulus decreased sharply with the increase of catechin content; on the contrary, the elongation changed slowly.

The FT‐IR spectra in the wave‐number 1 680–1 780 cm−1 region for blends of P(3HB‐co‐3HH)/catechin. A: HBH; B: HBHC10; C: HBHC20; D: HBHC30; E: HBHC40; F: HBHC50; and G: catechin.

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The FT‐IR spectra in the wave‐number 1 680–1 780 cm−1 region for blends of P(3HB‐co‐3HH)/catechin. A: HBH; B: HBHC10; C: HBHC20; D: HBHC30; E: HBHC40; F: HBHC50; and G: catechin.
Anionic Polymerization of Ethylene Oxide in the Presence of the Phosphazene Base ButP4 – Kinetic Investigations Using In‐Situ FT‐NIR Spectroscopy and MALDI‐ToF MS
Authors: Schmalz Holger , Lanzendörfer Michael G. , Abetz Volker , Müller Axel H. E.
Published: May 2003

Fourier‐transform near‐infrared (FT‐NIR) fiber‐optic spectroscopy was successfully used to monitor the anionic polymerization of ethylene oxide (EO). Kinetic data are provided for the polymerization of EO with the sec‐BuLi/ButP4 initiating system under different reaction conditions. In addition, the influence of different initiators and reaction conditions on the polymerization of EO is investigated. Online monitoring using NIR spectroscopy reveals an unexpected induction period present in EO homopolymerizations as well as in the synthesis of PEO containing block copolymers with [Li/ButP4]+ counterions. The resulting polymers are characterized by size exclusion chromatography (SEC). A low‐molecular‐weight polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) diblock copolymer was synthesized to gain more insight into the observed induction period by matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry (MALDI‐ToF MS) on samples taken during EO polymerization. The induction period is believed to be a result of different factors involved in the formation of active centers, for example, the break up of lithium alkoxide aggregates by the phosphazene base ButP4, and chain length effects. It depends on reaction temperature, concentration of the phosphazene base ButP4, as well as the structure of the initiator.

SEC traces for EO homopolymerizations using different initiating systems at 50 °C.

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SEC traces for EO homopolymerizations using different initiating systems at 50 °C.
Missions and Challenges of Polymer Science and Technology
Authors: Horie Kazuyuki
Published: May 2003

This section contains reports on topical conferences. Reports are usually written at the request of the editorial office, but unsolicited contributions are also welcome. Suggestions should be sent to the editorial office of the Macromolecular journals, preferably by E‐mail to macromol@wiley‐vch.de.
Solvent Effects, Diffusion Control and Mechanistic Aspects of Catalytic Chain Transfer Polymerization
Authors: Pierik Sebastiaan C. J. , Vollmerhaus Rainer , van Herk Alex M.
Published: May 2003

In the catalytic chain transfer polymerization of methyl methacrylate, butyl methacrylate and 2‐ethylhexyl methacrylate in toluene, it was found that the chain transfer constants (CT) were independent of solvent concentration and therefore of solution viscosity, and did not differ from the bulk polymerization values. For a diffusion controlled system, theoretical calculations predict an increase in CT when the solution viscosity is lowered. This points at a non‐diffusion controlled catalytic chain transfer step. These results were obtained when the solvent was thoroughly purified using a Grubbs‐type set‐up, whereas a large reduction in CT was found in unpurified solvent. Similar results were obtained for butyl acetate. Therefore it is concluded that the decrease of CT in non‐purified solvents is not related to the solvent itself, but to solvent impurities. Further we found that methyl methacrylate ended radicals do not covalently bind to the cobalt complex, in contrast to styrene and acrylate ended radicals.

Chain transfer constant for the CCT polymerization of 2‐ethylhexyl methacrylate in toluene, and predictions for diffusion controlled systems.

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Chain transfer constant for the CCT polymerization of 2‐ethylhexyl methacrylate in toluene, and predictions for diffusion controlled systems.
Anionic Ring‐Opening Polymerization of Propylene Oxide in the Presence of Phosphonium Catalysts at Various Temperatures
Authors: Rexin Ornulf , Mülhaupt Rolf
Published: May 2003

Anionic ring‐opening polymerization of propylene oxide in the presence of a potassium alkoxide initiator was accelerated by the addition of the bulky phosphonium salts tetrakis[cyclohexyl(methyl)amino]phosphonium‐, tetrakis[propyl(methyl)amino]phosphonium‐, and tetrakis[octyl(methyl)amino]phosphonium‐tetrafluoroborate. Dipropylene glycol (DPG) was partially deprotonated (5%) and used as initiator. The delocalization of the positive charge over five atoms promoted the formation of a separated ion‐pair, thus enhancing nucleophilicity and reactivity. The polymerization behavior of the counterions at varied temperatures was studied. Characterization of poly(propylene oxide)s by means of 1H NMR spectroscopy, size exclusion chromatography (SEC), and matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry (MALDI‐TOF‐MS) showed low polydispersities and the absence of by‐products and impurities. The degree of polymerization (DPn) for the polymers was in the range of 8–60 (Mn = 630–3 620 g · mol−1) and Mw/Mn obtained was 1.03–1.35 and 1.11–1.32 for MALDI‐TOF‐MS and SEC, respectively. Values calculated from the titration of hydroxyl groups (OHV) showed good agreement. Determination of the total degree of unsaturation in the range 13–60 mmol · kg−1 indicated larger amounts with decreasing polymerization rates and increasing polymerization temperatures.

The phosphonium salts Cy4PBF, Pr4PBF, and Oc4PBF.

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The phosphonium salts Cy4PBF, Pr4PBF, and Oc4PBF.
Biospecific Properties of Random Copolymers, 1
Authors: Bouzou Bérengère , Pflüger Fernando
Published: May 2003

The kinetic study of copolymer synthesis is important to understand how a material is built and how it can get some particular properties. The radical copolymerization of one, two or more monomers can be simulated with classical analytic models, but can also be simulated by a Monte Carlo model that allows a bigger flexibility and is a lot easier to compute and use. We have shown that this Monte Carlo simulation gives the same results of the kinetic study of the terpolymerization as the analytic model, and it can create easily a bank of virtual copolymers for all the compositions needed to analyze the structure of the macromolecular chains in terms of sequences of monomers occurring as a function of the global composition. The search for the sequences is very simple to compute as it consists in a simple reading of the virtual chains previously simulated. This result can thus be applied to make appear a simple correlation between the distribution of functional groups and some specific observed biological activities of biospecific copolymers.

Simplified schema of the numerical virtual terpolymerization.

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Simplified schema of the numerical virtual terpolymerization.
Adsorption Profiles of Long‐Chain Polymer in Semidilute Solutions Physisorbed to a Wall
Authors: Cifra Peter
Published: May 2003

Equilibrium concentration profiles for long macromolecules in solution strongly adsorbed to a flat wall were estimated by a combination of persistent reptation and partial chain regrowth using a configurational bias lattice Monte Carlo method. The profiles were obtained for various concentrations in the semidilute regime and different chain lengths. A master curve exists in a plot of the profile reduced by the bulk concentration as a function of the distance to the wall reduced by the correlation length estimated for the bulk concentration. Near the wall, the master curve follows a power law with an exponent predicted in the scaling theory. Compared to depletion profiles at a repulsive wall that require a small penetration length, no correction of the distance to the wall is needed for the adsorption profiles.

Reduced plot of ϕ(x)/ϕbulk vs. x/ξ for chain length N = 1 000 and five bulk concentrations above ϕ* indicated in legend. Slope with the exact exponent from scaling theory is shown for comparison.

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Reduced plot of ϕ(x)/ϕbulk vs. x/ξ for chain length N = 1 000 and five bulk concentrations above ϕ* indicated in legend. Slope with the exact exponent from scaling theory is shown for comparison.