Intramolecular self-templating

Internal templating refers to the self-selection of library members through intramolecular or intermolecular stabilizing noncovalent interactions. Intramolecular self-templating is observed when the species formed in a DCL are capable of folding upon themselves (Figure 1.2c). The library members that are best able to form favorable noncovalent interactions within themselves will be ampHfied in the library. DCC has therefore been used to study the folding of peptides, nucleotides, and synthetic polymers (Chapter 6). It can be used to direct the reversible... 

Receptor 15 has been designed for the complexation of barbiturates [ref 17]. The syndiesis was accomplished by Ba -templated macrocyclization of the appropiate dialdehyde and cis-l,2-cyclohexanediamine, followed by reaction with uranyl acetate. NMR experiments in CDCI3 revealed that intramolecular self-complexation takes place and a constant Kg if-ass for this process of IS has been estimated. The association constants of three barbiturates could be determined by NMR titrations in a mixture of CDC13 and DMSO-dg (95 5). The association constants of dimethyl, diethyl, and ethylphenyl barbituric acid are 112, 97, and 45 Imol respectively. It is obvious that a sterically more demanding barbiturate results in a lower association constant. The host 15 is able to transport barbituric... 

Among a variety of present stmctures, core-shell molecular bmshes that contain diblock copolymers in the side chains are of special interest. A judicious choice of the two blocks in the side chains may result in an intramolecular phase separation in solution due to their unlike interactions with the solvent. This can aeate a ID channel in the core surrounded by a protective shell. The anisotropically shaped core can be practically used as a nanoreactor to synthesize and accommodate ID inorganic or hybrid nanostmctures. According to the chemical nature of the core and shell, the templates can be classified roughly into three forms, namely, amphiphilic, bishydrophilic, and self-templating core-shell molecular bmshes. 

Figure 1.2 The different ways in which molecular recognition can exert control over library distribution selection may be through external templating by an added (a) guest or (b) host molecule, or though self-templating that is either (c) intramolecular or (d) intermolecular.

A typical example involves the perylene monoimide donors described above. They have been used to construct antenna models in which up to eight perylene units were covalently bound to a zinc(II) porphyrin94. Osuka and coworkers windmill porphyrins also present excellent antenna complex building blocks (vide infra)95. In addition, several porphyrin wheel antenna complexes were prepared by template-assisted synthesis96,97 or self-aggregation98. Intramolecular cyclization of porphyrin dodecamers to a porphyrin wheel has also been achieved99. 

Dynamin self-assembly stimulates its basal GTPase activity 10-100-fold in vitro (Barylko et al, 2001 Stowell et al., 1999 Tuma and Collins, 1994 Warnock et al., 1996). This is due to activation of dynamin s intramolecular GTPase activating protein (GAP, amino acids 618-752 of dynamin), which becomes activated upon dynamin self-assembly (Muhlberg et al., 1997 Sever etal., 1999). Most assays that measure assembly-stimulated GTP hydrolysis by dynamin use templates such as lipids to promote dynamin self-assembly (Barylko et al., 2001 Song et al., 2004 Stowell et al., 1999). In contrast, we have developed a soluble assay that reconstitutes assembly-stimulated GTP hydrolysis by simply adding recombinant isolated GAP domain to unassembled dynamin (Sever et al., 1999). Thus, recombinant GAP domain, on its own, stimulates GTP hydrolysis by dynamin approximately 100-fold (Sever etal., 1999). Pre-incubation of dynamin with auxilin prior to addition of the recombinant GAP domain abolishes GAP s ability to stimulate GTP hydrolysis. The GAP-stimulated assay that we routinely use is described. 

The formation of these nanotubes is totally reversible tube dissociation takes place after the elimination of the host, while new addition of the template once again promotes the nanotube self-assembly. Covalently stabilized nanotubes avoid the destruction of the nanotube after the elimination of the host (Figure 9b). Thus, two units of tris(3,5-pyridine) covalently bonded through a butyl spacer can self-assemble to form the nanotube, upon metal addition, without any template. The linker adopted a U-shaped conformation due to its flexibility upon intramolecular Pd coordination." This nanotube encapsulates aliphatic molecules, such as cyclohexane and octane. The use of a... 

Templates can also be classified according to tlie strength of interaction between the template and die substrates and the subsequent induced interaction between the bound substrates, as summaiised in Fig. 2. Classical templates bind non-covalently to their substrates, but assist in tlie fonnation of covalent bonds. A good example is the metal cation induced syntliesis of crown ethers. A closely related class includes templates in which intermolecular steps are transfonned into intramolecular ones by covalent bonding between template and substrates.[10] Self-assembly processes could also be classified as aggregation-templated, a non-covalent interaction between template and substrates inducing a second non-covalent interaction.[6, 7]... 

The spontaneous formation of the trefoil knot is a result of strong intramolecular hydrogen bonding interactions serving as a template that can be enhanced by the use of non-polar aprotic solvents such as dichloromethane. The efficacy of hydrogen bonding interactions in the mechanism of the trefoil knot formation was also confirmed through a step-by-step approach in which some of the precursors of the final structure were prepared independently and were shown to self-assemble into an open trefoil knot structure. ... 

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