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Involving Variation (involving + variation)
Selected AbstractsZinc-Salen-Catalyzed Asymmetric Alkynylation of Alkyl AcylsilanesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2009Feng-Quan Li Abstract Optically active tertiary propargylic alcohols are useful and versatile building blocks in organic synthesis, and their direct access by enantioselective addition of alkyne nucleophiles to ketones has achieved significant progress over the last ten years. In view of the potential applications of acylsilanes as useful synthetic equivalents of aldehydes, we described a general catalytic enantioselective addition of terminal alkynes to alkyl acylsilanes. After reaction optimization involving variation of solvent, temperature, catalyst ratio and various catalysts screen, the in situ generated Zn-salen complex was chosen as catalyst. With hexane as solvent, the silylated tertiary propargylic alcohols were obtained in satisfactory yields and ees for both aliphatic and aromatic alkynes. [source] Aggregating conclusive and inconclusive information: Data and a model based on the assessment of threatJOURNAL OF BEHAVIORAL DECISION MAKING, Issue 4 2010Joseph V. Baranski Abstract This study examined the process of combining conclusive and inconclusive information using a Naval threat assessment simulation. On each of 36 trials, participants interrogated 10 pieces of information (e.g., speed, direction, bearing, etc.) about "targets" in a simulated radar space. The number of hostile, peaceful, and inconclusive cues was factorially varied across targets. Three models were developed to understand how inconclusive information is used in the judgment of threat. According to one model, inconclusive information is ignored and the judgment of threat is based only on the conclusive information. According to a second model, the amount of dominant conclusive information is normalized by all of the available information. Finally, according to a third model, inconclusive information is partitioned under the assumption that it equally represents both dominant and non-dominant evidence. In Experiment 1, the data of novices (i.e., civilians) were best described by a model that assumes a partitioning of inconclusive evidence. This result was replicated in a second experiment involving variation of the global threat context. In a third experiment involving experts (i.e., Canadian Navy officers), the data of half of the participants were best described by the partitioning model and the data of the other half were best described by the normalizing model. In Experiments 1 and 2, the presence of inconclusive information produced a "dilution effect", whereby hostile (peaceful) targets were judged as less hostile (peaceful) than the predictions of the Partitioning model. The dilution effect was not evident in the judgments of the Navy officers. Copyright © 2009 Crown in the right of Canada. Published by John Wiley & Sons, Ltd. [source] Structural plasticity of peanut lectin: an X-ray analysis involving variation in pH, ligand binding and crystal structureACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2004S. Kundhavai Natchiar Until recently, it has only been possible to grow crystals of peanut lectin when complexed with sugar ligands. It is now shown that it is possible to grow peanut lectin crystals at acidic pH in the presence of oligopeptides corresponding to a loop in the lectin molecule. Crystals have also been prepared in the presence of these peptides as well as lactose. Low-pH crystal forms of the lectin,lactose complex similar to those obtained at neutral pH have also been grown. Thus, crystals of peanut lectin grown under different environmental conditions, at two pH values with and without sugar bound to the lectin, are now available. They have been used to explore the plasticity and hydration of the molecule. A detailed comparison between different structures shows that the lectin molecule is sturdy and that the effect of changes in pH, ligand binding and environment on it is small. The region involving the curved front ,-sheet and the loops around the second hydrophobic core is comparatively rigid. The back ,-sheet involved in quaternary association, which exhibits considerable variability, is substantially flexible, as is the sugar-binding region. The numbers of invariant water molecules in the hydration shell are small and they are mainly involved in metal coordination or in stabilizing unusual structural features. Small consistent movements occur in the combining site upon sugar binding, although the site is essentially preformed. [source] GABAC RECEPTOR ION CHANNELSCLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 11 2004M Chebib SUMMARY 1.,The present review gives an overview of studies conducted on GABAC receptors over the past 10 years since the author started at the University of Sydney. It concentrates on the structure,activity relationship profiles of the receptor and how these studies were used to: (i) develop selective GABAC receptor ligands; and (ii) understand the impact of amino acid changes on GABAC receptor pharmacology and function. 2.,Structure,activity relationship studies involving variations of both ligands and their receptor targets are vital to the discovery of drugs that interact selectively with particular native and mutant receptor subtypes. Such agents may be useful for treating anxiety, depression, epilepsyand memory related disorders, such as Alzheimer's disease. [source] | ||||||||||