Reversible Noncovalent Interactions

These data show that the polypeptide chain of /3-lactoglobulin has a molecular weight of 18.(XX). and that in high concentration, the protein exists as a dimer of Mr = 36,000. However, on dilution, the dimer, maintained by reversible, noncovalent interactions, undergoes a partial dissociation A2 2A. 

In fact, the large number of fascinating molecular architectures (Figure 5) formed from cucurbiturils lead to the concept of self-assembling capsules. These self-assembling capsules are receptors with enclosed cavities that are formed by the reversible noncovalent interaction of two or more, not necessarily identical, subunits. As would be in a subsequent section, the self-assembly of isolated calix[4]hydroquinone molecules leads to well-defined honeycomb architectures [64,65]. One of the advantages of these self-assembling capsules is that they can... 

Rebek has defined self-assembling capsules as receptors with enclosed cavities, formed by the reversible noncovalent interaction of two or more, not necessarily identical, sub-units [ll]. Consequently, the resulting capsule has a well-defined structure in solution, and shows binding capabilities that are absent for the individual components alone [11]. Examples provided in this section are restricted to capsules that form only in the presence of a template. As a result, unique sets of spectroscopic data are acquired for solutions of both the individual subunits in the presence and absence of the required templates. 

Supramolecular approaches to self-assembly often rely upon reversible noncovalent interactions. These strategies inherently involve an error-correction process, and as a consequence, the thermodynamically Savored structures are preferentially constructed.Particularly in the self-association of racemic components, the error-correction process often leads to the selective formation of the homochiral clusters, although the diastercomcric clusters with similar stability are potentially formed as the final products. ... 

More recently, the importance of introducing supramolecular interactions between macromolecular chains has become evident, and many new options have been introduced. The final step in this development would be to develop polymers based on reversible, noncovalent interactions. Rather than linking the monomers in the desired arrangement via a series of polymerization reactions, the monomers could be designed in such a way that they self-assemble autonomously into the desired stracture. As with covalent polymers, a variety of structures of these so-called supramolecular polymers are possible, with block-copolymers or graft copolymers - as well as polymer networks - being created in this way. 

Self-assembled molecular capsules are three-dimensional structures generated through reversible, noncovalent interactions such as hydrogen bonding between complementary subunits. They circumvent many problems of covalent capsules, such as multistep and complicated synthetic methods and lack of versatility. Therefore, recent researches are focused on self-assembled systans [2], Micelles, emulsions, vesicles, and noncovalent molecular capsules are examples of self-assembled NRs [2],... 

Molecules that are capable of spatial complementarity and weak reversible noncovalent interactions with each other can self-assemble from a less ordered state (such as a solution) to an ordered structure (such as a soUd crystal) without human intervention [113], In this manner, precise tuning of oligopeptide assodating structures provides an completely new route to a hierarchy of structures such as tapes, ribbons, fibrils, fibers, and fiber networks, which can be usefid as materials [114—... 

Supramolecular polymers are arrays of low-molecular-weight building blocks held together by hydrogen bonding or other reversible noncovalent interactions. Stiff stilbene (1, 1-biindane, Fig. 10.6) moiety, which exists as structurally distinct E and Z isomers, offers considerable advantages over azobenzene as a chromophore... 

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