Subject flexible substrates

The brittle cracking and subsequent debonding of films deposited on flexible substrates subjected to uniaxial strain is described theoretically and illustrated with Ni films evaporated on ion-etched polyethylene terephthalate (PET). It is shown that, if the materials deform elastically, the shear strength of the interface, x, may be evaluated from the length,... 

The majority of enzyme substrates contain flexible moieties. As the 3D structure of the substrate to be analyzed (the conformation) has a reasonable impact on the outcome of the method, a precise protocol is used to build it. Each substrate is subjected to a conformational search followed by energy minimization by means of a software developed at Molecular Discovery Ltd. The population of conformers is... 

To confront these difficult tasks, we have incorporated old and new solutions. For example, strong yet flexible Kapton polyimide substrates are promising, and the neutral-carrier type ion-selective membranes offer the advantage of using similar fabrication methods for sensors of different ions of interest. We are also working on the biocompatibility problems, and all new designs are subject to in vivo tests. 

The intramolecular nitrogen-trapping protocol used by Banwell has also been successfully exploited in the assembly of spirocyclic frameworks relating to the aromatic erythrina alkaloids.24 However, when it was applied to the synthesis of nonaromatic spirocycles, as found in histrionicotoxin, the flexible alkyl tether proved to be problematic.25 In this study, gem-dichlorocyclopropane substrate 37 was initially subjected to silver(I) salts under a variety of conditions only to provide solvolysis and elimination products without any indication of trapping by the pendent... 

The stereoselectivity of the hydride reduction of conjugated cyclohexenones has also been subjected to close examination from both experimental and theoretical viewpoints. Much of the work has involved polycyclic systems, e.g.. steroids which have little conformational flexibility and in which axial and equatorial directions of approach can be clearly defined. With small" hydride donors, these substrates show an even clearer preference for axial attack than the corresponding cyclohexanones. For examples involving reductions with lithium aluminum hydride and sodium borohydride, see Table 10. 3/(-Acetylcholest-5-en-7-one and cholest-2-en-l-one are notable in that the analogous saturated substrates are attacked from the equatorial direction115 l16. The reduction of 17/i-hydroxy-4-androsten-3-one (testosterone) to 4-androstene-3/1,17/j-diol with d.r. 90 10 can be compared with the sodium borohydride reduction of 17/i-hy-droxyandrostan-3-one (dihydrotestosterone) to androstane-3/ ,17/ -diol with d.r. 81 19 (see p 4030). 

Considerable knowledge exists about the nature of the active site of enzymes, their secondary, tertiary, and quaternary structures. In the case of those enzymes that have been obtained in crystalline form and subjected to X-ray analysis, conformational appearance has been deduced. However, the geometry of such an active site, as elucidated on an isolated crystalline enzyme, need not necessarily be complementary to the natural substrate, or drug molecule, to complex and interact with it. Since we visualize such a site as being flexible rather than rigid, the substrate or drug can induce such a complementary fit. 

Overall, the current picture is that while the P450 fold is conservative, it is quite flexible and can undergo rather large changes in response to the requirements of substrate specificity. The F/G helical region and B helix are subject to the greatest structural variation as well as flexibility. This is understandable considering the importance the... 

Film properties of these products are crucial to performance, and several methods to evaluate him properties of hairspray products have been developed [59, 68, 69]. Erlemann [59] has described a variety of methods both subjective and objective to evaluate hairspray hlms formed on different substrates including metal plates or glass, on flexible foils or tissues, and on hair. Ayer and Thompson [68] have described their evaluation of hairspray properties by scanning electron microscopy. 

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