Supramolecular nanoreactor

TABLE 7.1 Catalytic Tests for the Competitive Coupling of Pairs of Amines with one Acid and Pairs of Acids with one Amine Mediated by the Carbodiimide Cationic Condensing Agent in the Presence or Absence of the Hexameric Capsule as Supramolecular Nanoreactor at 60°C, Time 18 h. + Presence Absence... 

An excellent example where a capsid virus has been given a new supramolecular application can be found in the work of Nolte who took an icosahedral capsid virus, cowpea chloritic mottle virus (CCMV) and used it as a nanoreactor for polymer synthesis [30], Natural CCMV spontaneously assembles in acidic aqueous solution and disassembles in basic solution. The capsid contains pores open at pH 5 to release RNA into the host. Once the RNA leaves, the empty capsule is left. The Nolte group was able to assemble the subunits around polystyrene sulfonate with a mass of 9.9 kDa but the resulting structure had a different morphology to the natural system. Indeed, capsules formed around polymers with masses between 2 and 85 kDa but not around those with masses above 100 kDa. This raised the question of the potential for polymers to form within a capsid but to test the possibility a mixture of botanical, biological and chemical approaches was needed. 

Later, more sophisticated supramolecular complexes capable of improved molecular recognition started to be studied. New supramolecular approaches to constmct synthetic biohybrid catalysts were developed [190]. An example is the giant amphi-philes, formed by a (hydrophilic) enzyme headgroup and a synthetic apolar tail. These biohybrid amphiphilic compounds self-assemble in water to yield enzyme fibers and enzyme reaction vessels (nanoreactors [202]). 

A. Modification of Proteins (Enzymes) and Their Supramolecular Design in Reverse Micelles (Nanoreactors)... 

Although the research field is still in its infancy, several examples of reactions, wherein self-assembled nanoreactors are applied and are shown to dramatic enhance or alter reactivity, have appeared, thereby demonstrating the power of the supramolecular concept. Detailed studies are required to fully understand the mechanisms behind the effects observed when carrying out reactions in nanoreactors. The results obtained so far sketch a bright prospective, as reactions have been observed that are unique to those carried out in capsules. In this review we have focussed on reactions that take place inside the capsules. However, molecular capsules have also been used to control reactions that take place outside the capsule for example by controlling the release of reagents, making the nanoreactor applications virtually unlimited. ... 

In addition, it can be foreseen that supramolecular chemistry will play a key role in the development of stimuli-responsive vesicles. Stimuli-responsive vesicles will be important elements of sensors, nanoreactors, and drug... 

One particular asset of structured self-assemblies is their ability to create nano- to microsized domains, snch as cavities, that could be exploited for chemical synthesis and catalysis. Many kinds of organized self-assemblies have been proved to act as efficient nanoreactors, and several chapters of this book discnss some of them such as small discrete supramolecular vessels (Chapter Reactivity In Nanoscale Vessels, Supramolecular Reactivity), dendrimers (Chapter Supramolecular Dendrlmer Chemistry, Soft Matter), or protein cages and virus capsids (Chapter Viruses as Self-Assembled Templates, Self-Processes). In this chapter, we focus on larger and softer self-assembled structures such as micelles, vesicles, liquid crystals (LCs), or gels, which are made of surfactants, block copolymers, or amphiphilic peptides. In addition, only the systems that present a high kinetic lability (i.e., dynamic) of their aggregated building blocks are considered more static objects such as most of polymersomes and molecularly imprinted polymers are discussed elsewhere (Chapters Assembly of Block Copolymers and Molecularly Imprinted Polymers, Soft Matter, respectively). Finally, for each of these dynamic systems, we describe their functional properties with respect to their potential for the promotion and catalysis of molecular and biomolecu-lar transformations, polymerization, self-replication, metal colloid formation, and mineralization processes. 

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