Shape host-guest systems

Further investigation of this host-guest system showed not only that different guests could be incorporated in one host, but also that guest molecules of different size could be liberated in a shape selective fashion [168, 169]. 

In some instances, the interactions of various molecular regions in a macromolecule RM or in a composite "supramolecule" of a host-guest system are of interest. In these cases, a local shape analysis of the "isolated" RIDCO surfaces GR(a) is no longer sufficient, and the study of the interactions requires... 

The electron densities of local regions of both small and large molecules can be studied in detail using some of the macromolecular quantum chemical computational techniques developed recently. The shape analysis of host-guest systems and the comparison of the electron densities of interacting and noninteracting molecular regions provide measures and detailed descriptions of these interactions. 

Of course, for many host-guest systems the distinetion between structural and electronic effects is not necessarily clear cut. It is the subtle interplay between both the nature and shape of the respective potential energy surfaces of the two (or more) molecules in a host-guest system that will control both molecular recognition and binding strength. 

The formation of host-guest systems may occur as a result of a variety of interactions deriving from the size, shape, and electronic properties of the two partners. 

A useful approach for the synthesis of highly ordered host-guest systems is based on the use of macrocycles. One of these systems makes use of the couple cyclo[12]thiophene 9 and Ceo fullerene, which are a ring-shaped p-type and a spherical n-type organic semiconductor, respectively [41, 55], Compound 9 and Ceo self-assemble on HOPG as demonstrated by STM imaging (Figure 13.3). The deposition was realized... 

Fluorescence correlation spectroscopy can be used to measure the binding dynamics of host-guest complexes when the fluorescence quantum yields for the free and bound hosts are different. Analysis of fluorescence correlation spectra depends on the profile for the excitation pulse, which impacts the shape of the emission profile and mechanistic assumptions are made with respect to the diffusion of the various species in solution.58 For each chemical system different assumptions are made. 

Abstract This chapter updates but mostly supplements the author s Ange-wandte Review,111 setting in context recent advances based on protein and nucleic acid engineering. Systems qualify as a true enzyme mimics if there is experimental evidence for both the initial binding interaction and catalysis with turnover, generally in the shape of saturation kinetics. They are discussed under five broad headings mimics based on natural enzymes, on other proteins, on other biopolymers, on synthetic macromolecules and on small-molecule host-guest interactions. 

Noncovalent interactions play a special role in synthetic procedures used to assemble various types of supramolecular species. These syntheses rely on the stabilization provided by non-covalent interactions between recognition sites incorporated within precursors. Various types of non-covalent interactions can be used as a recognition motif utilized to guide the synthesis.Targeted synthesis of macro- and supramolecular structures of various sizes, shapes, and functionality has now become possible. Supramolecular chemistry offers incredible applications in various fields such as medicinal chemistry (drug delivery systems),host-guest chemistry,catalysis,and molecular electronics. ... 

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