Modular nature

The modular nature of the sensor allows the design of different sensors based on this concept. Fluorogenic calix [4]arenes (1, Fig. 7) bearing a pendent ethyleneamine on... 

There are certain catalyst systems which appear to be more amenable to combinatorial studies than others. For example, libraries of small peptides as ligands are particularly easy to prepare (e.g., on solid supports), and due to their modular nature high diversity is possible. High diversity is also readily achieved when using mixtures of two or more chiral monodentate ligands.122 This novel approach offers many perspectives. 

Hayashi, C. Y., and Lewis, R. V. (1998). Evidence from flagelliform silk cDNA for the structural basis of elasticity and modular nature of spider silks. J. Mol. Biol. 275, 773-784. 

Protein domains are the common currency of protein structure and function. Protein domains are discrete structural units that fold up to form a compact globular shape. Experiments on protein structure and function have been greatly aided by consideration of the modular nature of proteins. This has allowed very large proteins to be studied. The expression of individual domains has allowed the intractable giant muscle protein titin to be structurally studied (Pfuhl and Pastore, 1995). Protein domains can be found in a variety of contexts, (Fig. 1), in association with a range of unrelated domains and in a variety of orders. Ultimately protein domains are defined at the level of three-dimensional structure however, many protein domains have been described at the level of sequence. The success of sequence-based methods has been demonstrated by numerous confirmations, by elucidation of the three-dimensional structure of the domain. 

Because of the modular nature of fuel cells, they are attractive for use in small portable units, ranging in size from 5 W or smaller to 100 W power levels. Examples of uses include the Ballard fuel cell, demonstrating 20 hour operation of a portable power unit (32), and an IFC military backpack. There has also been technology transfer from fuel cell system components. The best example is a joint IFC and Praxair, Inc., venture to develop a unit that converts natural gas to 99.999% pure hydrogen based on using fuel cell reformer technology and pressure swing adsorption process. 

Before leaving this section we consider a slightly different optimization problem that may also be expensive to solve. In flowsheet optimization, the process simulator is based almost entirely on equilibrium concepts. Separation units are described by equilibrium stage models, and reactors are frequently represented by fixed conversion or equilibrium models. More complex reactor models usually need to be developed and added to the simulator by the engineer. Here the modular nature of the simulator requires the reactor model to be solved for every flowsheet pass, a potentially expensive calculation. For simulation, if the reactor is relatively insensitive to the flowsheet, a simpler model can often be substituted. For process optimization, a simpler, insensitive model will necessarily lead to suboptimal (or even infeasible) results. The reactor and flowsheet models must therefore be considered simultaneously in the optimization. 

The iridium complexes used as precatalysts are air-stable and easy to handle. A further attractive feature is the modular nature of the chiral ligands, which makes it possible to tailor the catalyst structure for a specific substrate. So far several unfunctionalized and functionalized olefins have been hydrogenated with good to... 

Miller and co-workers have exploited the highly modular nature of peptide structures, along with mechanistic knowledge regarding peptide conformational control and the principles of nucleophilic catalysis to develop an assortment of synthetically unique, useful, and practical asymmetric transformations [22]. Representative examples are illustrated in Scheme 7. Particularly noteworthy is the asymmetric phosphorylation the resultant phosphate ester can be readily... 

The modular nature of holoenzyme catalysis allows coenzyme B12 to be used in a variety of biological reactions with different apoenzymes. These reactions can involve homolysis of the Co—C bond to give an alkyl radical resulting in radical induced rearrangements, redox reactivity via reduction to Co (II) and Co (I), and alkylations. The nature of the coenzyme determines the type of the reaction, while the nature of the apoenzyme determines the selectivity of the reaction in terms of the substrate and the regiospecificity. 

Reliable capital and operating cost comparisons between pervaporation and distillation are not available. Pervaporation is less capital and energy intensive than distillation or adsorption processes for small plants treating less than 5000 L/h of feed solution. However, because of the modular nature of the process, the costs of pervaporation are not as sensitive to economies of scale as are the costs of distillation and adsorption processes. Distillation costs, on the other hand, scale at a rate proportional to 0.6-0.7 times the power consumption. Thus, distillation remains the most economical process for large plants. The cross-over point at which distillation becomes preferable to pervaporation from an energy and economic point of view currently appears to be 5000 L/h processing capacity. Bergdorf has made an analysis of the comparative costs of pervaporation, distillation and other processes [43],... 

Sigman and co-workers developed a novel oxazoline-based hydrogen-bonding catalyst (122) for HDA reactions. The modular nature of the catalyst design al-... 

In contrast, the Hoveyda and Snapper groups reported the efficient catalysis of silver acetate complexes of imine 204.86 These authors first established the superior performance of IV-ort/zo-methoxyaniline-substituted imines in the reaction with Danishefsky diene 195. Because of the modular nature of ligand 206, optimization of its structure could be achieved by surveying a combinatorial library of amino acid derivatives. The /-isoleucine para-methoxyaniline conjugate 206 proved the best. This ligand facilitated full conversion within 2-3 h with high yield and enantioselectivity (Scheme 2.53). 

To be useful for commercial devices, chromophores must be synthesized by high-yield, cost-effective chemical pathways. Fortunately, the modular nature of chromophores permits a variety of structures to be explored and workhorse reaction schemes to be optimized. In Schemes 1-4 we illustrate the synthesis of the chromophores of Fig. 7. 

Fig. 5. Schematic of the construction and function of chimeric restriction endonucleases (Chandrasegaran and Smith, 1999). (a) The type IIS restriction enzyme Fokl has a nonspecific endonuclease domain (FN) and a DNA-binding domain. Swapping Fokl s DNA binding-domain for that of another DNA binding-domain results in a chimeric restriction enzyme with new specificity. The flexibility resulting from less intimate contact between the Fn domain and its new DNA-binding domain translates into DNA cleavage at several locations near the binding site, (b) The modular nature and tunable specificity of zinc...

These transformations provide an indication of how different salen and metal combinations have been developed to optimize enantioselectivities and efficiency diverse reactions. The modular nature of the salen ligand allows... 

The half-wave potential for the enzyme-bound Co VCo cobalamin couple of the methionine synthase from E. coli at 526 mV versus SHE is about 80 mV lower than that of the Co /Cokcobalamin couple in neutral aqueous solution. Access to the catalytic cycle of the enzyme by one-electron reduction of Co kcobalamin (and reactivation upon occasional adventitious formation of Co -cobalamin) is indicated to be accomplished by a unique mechanism. The (thermodynamically unfavorable) reduction with intermediate formation of the enzyme-bound Cokcobalamin is driven by a rapid methylation of the highly reduced Co -center of the reduced corrin with Y-adenosyhnethionine. The modular nature of methionine synthase allows for the control of the methyl-group transfer processes by modulating and alternating conformational equilibria. ... 

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