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Cooperative Action (cooperative + action)
Selected AbstractsDeslipping of Ester Rotaxanes: A Cooperative Interplay of Hydrogen Bonding with Rotational BarriersEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2003Petra Linnartz Abstract A series of rotaxanes has been synthesized which contain two ester groups in their axles. All rotaxanes bear the same tetralactam wheel. The kinetics of the de-slipping reaction of these rotaxanes were monitored in tetrachloroethane (TCE) and dimethyl sulfoxide (DMSO) resulting in the observation of a significant solvent effect. In TCE, two isomeric rotaxanes that differ merely with respect to the orientation of the ester groups show a remarkable difference in their deslipping behavior. When the ester carbonyl group is directly attached to the axle center piece, the rotaxane decomposes with a half life of ca. 10 h at 100 °C. The reverse orientation with the carbonyl group attached to the stopper blocks deslipping almost completely and a lower limit for the half life at 100 °C of 25,000 h was obtained. These results can be interpreted by inferring a cooperative action of hydrogen bonding between wheel and axle and differences in rotational barriers. Molecular modeling and AM1 calculations support this interpretation. The implications of these results for the determination of steric size and the optimization of molecular machines are discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Ruthenium(II)-Catalyzed Regioselective Synthesis of Allyl Ketones from Alkynes and their Silver(I)-Catalyzed Hydroarylation into ,-Functionalized KetonesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009Min Zhang Abstract The regioselective synthesis of ,,,-unsaturated ketones from terminal alkynes is achieved by cooperative action of tris(acetonitrile)pentamethylcyclopentadieneruthenium hexafluorophosphate [Cp*Ru(NCMe)3+ PF6,] and para -toluenesulfonic acid catalysts. These allyl ketones undergo direct regioselective hydroarylation/Friedel,Crafts reaction to introduce an electron-rich aryl group at the ,-position in the presence of ligand-free silver triflate (AgOTf) catalyst. Both catalytic reactions take place with atom economy and provide an alternative to the synthesis of a variety of allyl ketones and , -arylated ketones. [source] How does acantholysis occur in pemphigus vulgaris: a critical reviewJOURNAL OF CUTANEOUS PATHOLOGY, Issue 6 2006Alessandro Lanza Background:, Pemphigus vulgaris is a life-threatening autoimmune blistering disease targeting skin and mucous membranes, characterized by disruption of keratinocytes' adhesion termed acantholysis. Today multiple classes of targets are considered to play a role in the genesis of the acantholysis; of these, the classical pemphigus antigens, desmosomal cadherins (desmoglein 1 and 3) are the best characterized and considered as the most important. Additional antigens include the novel epithelial acetylcholine receptors (,9 and pemphaxin). Thus, acantholysis in pemphigus seems to result from a cooperative action of antibodies to different keratinocyte self-antigens, but the mechanisms by which epithelial cleft occurs are not yet clearly understood. In fact, the binding of the autoantibodies to these targets generates a plethora of biological effects due, on one hand, to their direct interference with adhesive function and, on the other, to more complex events involving intracellular pathways that modify proteases activity or calcium metabolism, leading to loss of cell,cell adhesion. [source] The regulation of HIV-1 transcription: Molecular targets for chemotherapeutic interventionMEDICINAL RESEARCH REVIEWS, Issue 5 2006Miguel Stevens Abstract The regulation of transcription of the human immunodeficiency virus (HIV) is a complex event that requires the cooperative action of both viral and cellular components. In latently infected resting CD4+ T cells HIV-1 transcription seems to be repressed by deacetylation events mediated by histone deacetylases (HDACs). Upon reactivation of HIV-1 from latency, HDACs are displaced in response to the recruitment of histone acetyltransferases (HATs) by NF-,B or the viral transcriptional activator Tat and result in multiple acetylation events. Following chromatin remodeling of the viral promoter region, transcription is initiated and leads to the formation of the TAR element. The complex of Tat with p-TEFb then binds the loop structures of TAR RNA thereby positioning CDK9 to phosphorylate the cellular RNA polymerase II. The Tat-TAR-dependent phosphorylation of RNA polymerase II plays an important role in transcriptional elongation as well as in other post-transcriptional events. As such, targeting of Tat protein (and/or cellular cofactors) provide an interesting perspective for therapeutic intervention in the HIV replicative cycle and may afford lifetime control of the HIV infection. © 2006 Wiley Periodicals, Inc. Med Res Rev, 26, No. 5, 595,625, 2006 [source] Problem Representation and Conflict Dynamics in the Middle East and Northern IrelandFOREIGN POLICY ANALYSIS, Issue 3 2005Donald A. Sylvan In an effort to explain conflictual and cooperative actions in the Middle East and Northern Ireland at a time (1995,1999) when international structural factors were relatively constant, this article focuses on cognitive factors. Specifically, statements of leaders representing multiple actors in the Israeli,Palestinian and Northern Ireland relationship are examined. Texts from these leaders serve as data for the independent variable, problem representation. Hypotheses argue that the existence and centrality of actor problem representations can help explain behavior, in a manner that adds to more widely used scholarly explanations. More specifically, the article explores the relationship among leaders' "problem representations" and conflict between the entities they lead. Problem representation is measured in three dimensions using Foreign Broadcast Information Service (World News Connection) texts: (1) centrality of enemy image, (2) how inclusive/exclusive the leader is in describing the in-group and principal outgroup, and (3) the key definition of the problem (coded in terms of three strategies: justice, governance, or threat). Conflict, the dependent variable, is measured in terms of KEDS-TABARI event data on deeds (not words) in the Israeli,Palestinian and Northern Ireland conflicts. Strikingly, the analysis finds that Israeli actions are strongly related to prior and current Palestinian leaders' problem representations, much more than they are to Israeli leaders' problem representations. Similarly, Palestinian actions are found to have a clear relationship with prior and current Israeli leaders' problem representations, much more than they are with Palestinian leaders' problem representations. These results are particularly strong when the problem representation is one of the overall political leadership on the "other" side. Additionally, in-group and out-group inclusivity are the most significant predictors of actions. For Northern Ireland, the same two themes prevail, although not as strongly: there is a clear statistical relationship between each side's problem representations and the other side's actions, stronger in fact than the relationship between their own side's representations and actions. Also, in-group and out-group inclusivity produce a strong statistical relationship with conflict and cooperation. Finally, results are compared with a "tit-for-tat" hypothesis, and found to embellish that hypothesis. [source] Best Practices to Reduce Migration PressuresINTERNATIONAL MIGRATION, Issue 3 2002Philip Martin Are there best practices to foster economic development, reduce population growth, and protect the environment in source countries of unauthorized migration, in a manner that reduces emigration pressures and redirects migration towards legal channels? This paper outlines cooperative actions that can be undertaken by both source and receiving countries to better manage the movements of people over national borders. There are two broad approaches to foster wanted migration and to reduce unwanted migration. First, maximize migration's payoffs by ensuring that the 3 Rs of recruitment, remittances, and returns foster economic and job growth in emigration areas. Second, make emigration unnecessary by adapting trade, investment and aid policies, and programmes that accelerate economic development and thus make it unnecessary for people to emigrate for jobs and wages. Most of the changes needed for stay,at,home development must occur in emigration areas, but immigration areas can cooperate in the management of immigration, guest workers, and students, as well as in promoting freer trade and investment, and in targeting aid funds. In a globalizing world, selective immigration policies may have important development impacts, as with immigration country policies toward students, and workers in particular occupations, such as nurses and computer programmers, as well as with mutual recognition of occupational licenses and professional credentials. Trade policies affecting migration are also important, such as trade in services and laws regulating contracts between firms in different countries that allow the entry of lower wage workers as part of the contract. opening channels for legal migration can deter irregular migration. [source] | |||||||||||||