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The selective oxidation of alkane and olefin moieties are reactions of fundamental importance in both chemical synthesis and biology. Nature efficiently catalyzes the oxidation of hydrocarbons using iron-dependent enzymes, which operate through the mediation of oxoiron(IV) or oxoiron(V) species. In the quest for chemo, regio and stereoselective transformations akin to those taking place in nature, bioinspired iron catalysts have been developed and understanding their mechanism of action has become a particularly relevant area of research. While a prominent advance in the preparation and characterization of oxoiron(IV) species has been accomplished, oxoiron(V) species remain exceedingly rare, presumably because the high reactivity that makes them particularly interesting also makes them difficult to observe. This review summarizes the advances in the field, focusing in synthetic systems for which the oxoiron(V) species relevant in these transformations have been directly detected and spetroscopically characterized.  相似文献   
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The building industry is noted for its repeated building defects causing cost increases and time delays during construction. In Spain, despite the Ley de Ordenación de la Edificación (Building Regulation Act), which establishes a general framework to promote overall building quality, construction defects in residential buildings remain a pervasive problem. An analysis of 3647 construction defects is presented which identified the location within the building, subcontractors and building element in 68 residential building developments undertaken by two large Spanish contractors. The research reveals that the most common defects that arise during construction are related to the stability of the structure and inappropriate installation of roofs and facades. These technical faults are caused by poor workmanship rather than by the quality of the materials or products used. By comparing these results with a previous study on defects after handover, it can be concluded that while the nature of defects during construction is basically technical, at handover it is aesthetic or technical.  相似文献   
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Coupling of side chain dynamics over long distances is an important component of allostery. Methionine side chains show the largest intrinsic flexibility among methyl-containing residues but the actual degree of conformational averaging depends on the proximity and mobility of neighboring residues. The 13C NMR chemical shifts of the methyl groups of methionine residues located at long distances in the same protein show a similar scaling with respect to the values predicted from the static X-ray structure by quantum methods. This results in a good linear correlation between calculated and observed chemical shifts. The slope is protein dependent and ranges from zero for the highly flexible calmodulin to 0.7 for the much more rigid calcineurin catalytic domain. The linear correlation is indicative of a similar level of side-chain conformational averaging over long distances, and the slope of the correlation line can be interpreted as an order parameter of the global side-chain flexibility.  相似文献   
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