Organic scaffold

Peptide and protein scaffolds offer a means to influence coenzyme reactivity without some of the Hmitations of the host organic scaffolds described above. Both proteins and peptides can be used to generate complex chemical environments. Existing proteins, which already contain structural complexity, can be... 

Rapid burnout of the organic scaffold causes registration of higher than normal contents of elements... 

Metal-containing compounds provide new opportunities for designing unique and defined 3D globular structures and thus complement molecular diversity created by purely organic scaffolds. In this respect, a key requirement is the kinetic stability of... 

Fig. 1. Schematic illustration of a series of constrained cyclic peptides collectively sampling the broad conformational space of a linear analog. The rectangles, triangles, etc. represent organic scaffolds that force peptides into different conformational substates.

Synthesis of organic compounds on solid support was first reported for peptide synthesis in the 1960s (18). In solid-supported (or solid phase ) synthesis, the starting organic scaffold is covalently bonded to an insoluble polymer support, generally a functionalized polystyrene derivative. Reagents and build-... 

Examples of substituted synthetic hemes as their iron(II) complexes where close face-to-face approach of another heme is forbidden by the organic scaffolds introduced (and highlighted), allowing the small dioxygen molecule to bind reversibly at the protected axial site. 

Composite materials can be formed by numerous methods. Two modes in which incorporation of the inorganic material in the template can be achieved will be discussed sol-gel processes or nanoparticle infiltration. They are both solution methods that can be processed at low temperatures, hence allowing the use of polymeric templates. In the first method the sol-gel chemistry is performed after the incorporation of a metal oxide precursor in the polymer matrix or around the template entities. The second method makes use of preformed metal oxide nanoparticles, which are infiltrated into the organic scaffold or suspended in solution with the individual structures for controlled adhesion. 

Similar templates with solvent swehing properties have been used for nanoparticle infiltration [10]. The acryfic acid/2-hydroxyethylmethacrylate copolymer was soaked in a colloidal sol of 4.5 wt%, 8 nm titania anatase particles for 7 weeks. Thermal treatment to remove the organic scaffold and induce condensation of surface hydroxyl groups between contacting nanoparticles, gave porous titania monoliths. 

As we have seen. calix[4]arenes offer an organic scaffold upon which receptors may be constructed. Gale. Loeb, and coworkers also used a platinum tetrapyridine complex as an inorganic scaffold with which to arrange amide groups in space. The square planar Pt(II)... 

As discussed earlier briefly, semicrystalline or amorphous nanotubes can be obtained from 3D compounds and metals by depositing a precursor on a nanotube template intermediately, and subsequently removing the template by calcination. If the template molecules are not removed and they are able to effectively passivate the dangling bonds of the compound, a perfectly crystalline nanotube composite can be obtained. However, after high-temperature calcination, the organic scaffold is removed and the inorganic oxide remains. Because a nanotube is the rolled-up structure of a 2D-molecular sheet, there is no way that all the chemical bonds of the 3D-inorganic compound will be fuUy satisfied on the nanotube inner and outer surfaces. Furthermore, the number of molecules increases with the diameter, and hence a full commensuration between the various molecular layers is not possible. Therefore, nanotubes of 3D... 

MacMillan et al. demonstrated the power of a Diels-Alder reaction for the construction of complex organic scaffolds toward efficient natural product synthesis. They recently developed a cascade reaction, including an asymmetric DA between indol derivatives 23 and propargyl aldehyde catalyzed by 24 or 25 as the key step (Scheme 6.5) [20]. Depending on X (S or Se), the cascades proceed through different paths to give the different polycychc natural product precursors 26 and 27. 

Nuclear matrix A protein web that is left in the nucleus when histones and other weakly bound proteins are removed and most of the DNA is digested away. It is presumed to act as an organizing scaffold for the chromatin. 

The successes of conducting polymers are considerable, and more are certain to come. After decades of intense research, both theoretical and experimental, organic-based materials that are electrically conductive, a property usually associated with metals, have been prepared and are now articles of commerce. Can magnetism, another property not normally associated with organics, be coaxed onto an organic scaffold ... 

---