Rigid template structures

Feldman et a .210 211 and Wulff et ul v have examined other forms of template controlled oligomerization of acrylic monomers. The template (23) has initiator and transfer agent groups attached to a rigid template of precisely defined structure.210 "11 Polymerization of MMA in the presence of 23 gave a 3 unit oligo(MMA) as ca 66% of the polymeric product. The stereochemistry of the oligomer was reported to be different" from that of atactic PMMA. 

As the ladderanes have rigid rodlike structures consisting of C-C a bonds, they have been used as spacer for electron-transfer reactions32,33 and as templates for controlling oligomerization.34... 

Despite their simplified structures, most of the tripodal based chelators exhibit iron binding with pronounced affinity, facilitate synthesis and allow fast screening of a variety of related structures with a number of bacterial types in a relatively short time. There is, however, a clear distinction between the flexible and the rigid templates. While the former generally exhibit broad spectrum microbial activity, the latter are generally less active and frequently show no biological activity at all. 

The use of templates that can nucleate secondary structures has also been studied [23], The fundamental idea is to attach one or more conformationally flexible peptides to a rigid template that is designed to initiate either a /f-sheet or an a-helix by forming the first crucial hydrogen bonds. These interactions compensate for the loss of entropy associated with the folding process and in particular in the initiation step. This strategy has been used to develop stable helices, sheets, and artificial proteins. 

The ortho- and para carboxylic acid substituted tetraphenyl porphyrins were used by Nishino and coworkers [36] to prepare the well defined 4-a-helix structures 42 and 43, which are soluble in lipid bilayer membranes. The rigid template of 42 provides some stability to the bundle structure (as measured by... 

However, a number of biological findings could not be explained by the CPCA analysis. The authors attribute this to the fact that the ephrin-Eph kinase interactions are best described by an induced fit mechanism. The necessary computational assumption of keeping the protein structure rigid did not reflect the flexibility of the protein interfaces and their structural adaptability. The homology models, on the other hand, provided a rigid protein structure that is biased by the template protein EphB2. 

A key problem is the in vivo synthesis of chemicals such as proteins and nucleic acids with rigidly specific structures. Spiegelman (1928) gives a clear review. The template theory, which he favors, has ample opportunity for H bond participation. Enzyme action is also conceived as a template reaction (1584). In this case, somewhat less matching is needed, in comparison with the synthesis of genetic material. The enzyme and substrate need fit over only a fairly small percentage of their surface (50). Hydrogen bonds may help achieve this match and thus influence the specificity of the reaction. 

The use of double hydrophilic block copolymers in biomimetic mineralization processes has been investigated in recent years. In contrast to rigid templates (like carbon nanotubes and porous aluminum templates which predefine the final structure) water soluble polymers could be used as soluble species at various hierarchy levels. Usually, in the case of DHBCs, one of the block acts as scaffold for the development of the crystal, while the other acts as a soluble-stabilizing matrix. Therefore, both of the blocks play a crucial role on the development of the crystals. There is a plethora of reports on the emerging bio-inspired mineralization field. Various crystal structures have been presented during the last years, following versatile synthetic routes. A very detailed and illustrious review has been recently given by Colfen [3]. The above review describes in detail all aspects of the specific field. Herein, we present just a few selected examples. 

This tri-partite structure is not meant as a rigid template for contextualizing engineering education. Our organization is patterned on Sheppard et al. (2009). 

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