Assembly of Supramolecular Structures

Many supramolecular structures are formed largely by the stepwise noncovalent association of macromolecules, such as proteins. The processes of assembly are governed by the same chemical and physical principles that govern protein folding and the formation of quaternary structures (see Chap. 4). The driving force for the assembly process generally depends on the formation of a multitude of relatively weak hydrophobic, hydrogen and ionic bonds that occur between complementary sites on subunits which are in van der Waals contact with each other. In addition, covalent 

Conformational changes within and between subunits are frequently essential to the assembly process. These conformational changes are often critical to the overall stability of the final structure with respect to the individual components. They can also strongly contribute to the highly cooperative nature of the assembly of supramolecular structures as well as contribute to the proper orientation of subunits with respect to one another. 

In some cases, the assembly process is brought about by the association of a number of identical subunits to form a complex structure. This stepwise assembly process has certain advantages. First, it reduces the amount of genetic information needed to code for a complex structure, and second, it allows mistakes to be circumvented if faulty subunits can be excluded from the final structure (see Prob. 5.1). 

When all of the information for assembly of a supramolecular structure is contained within the component molecules themselves, the process is termed self-assembly. 

Ribosomes are large macromolecular complexes whose components contain all the information necessary for self-assembly. The E. coli ribosome has a sedimentation coefficient of 70 S and consists of two subunits (50 S and 30 S) with a total mass of 2.8 x 106 Da and with 58 different components. Three of these components are RNA molecules that together comprise 65 percent of the mass and they act as a framework or template for the ordering of the different proteins. When the pure dissociated components are mixed together in the proper order under the correct conditions they spontaneously reassemble to form a fully active ribosome (Fig. 5-1). 

---

Chalcogen-Halogen Secondary Bonds in Self-Assembling of Supramolecular Structures... 

David N. Reinhoudt Jerusalem, Israel Synthesis and Self-Assembly of Supramolecular Structures for Switches and Sensors... 

The generation of supramolecular structure of interest usually relies on molecular self-assembly and auto-organization processes. Much attention has been recently focused on the design of nanometer-scale (nanoscale) molecular devices. One approach to the molecular devices is the self - assembly of supramolecular structures such as the inclusion complexes [1,2,7,8],... 

In addition to the function of ordered hydrogen bonded arrays in the biological cell [42], the design of new materials is closely connected with the organised self-assembly of supramolecular structures [43]. The physical and chemical properties of molecular aggregates depend on the nature of the constituent molecules as well as on the manner in which the molecules assemble in the solid state. This is because the properties and architectural features of the supramole-... 

Locking self-assembly of supramolecular structures possessing heterocyclic fragments 07CSR856. 

The assembly of supramolecular structures by peripheral coordination of transition metal complexes is a very versatile approach, as will be shown below using essentially the same pyridylporphyrins presented in the previous section. Many intrincate new architectures can be built-up generating exquisite nanosized... 

The self-assembly of supramolecular structures such as host-guest inclusion complexes has r ently bem the focus of a number of research efforts. This approach allows the d ign and building of nanoscale molecular device. It constitutes a conveni t route to realizing the polymerization of hydrophobic molecules (guests) such as thiophene derivatives in aqueous soluticm by using CDs (hosts) and to customizing the polymer ardiitectures 9-11). 

Figure 1 Noncovalent interactions that dominate assembly of supramolecular structures in biology, (a-d) Hydrogen bonding, electrostatic, jr-cation and van der Waals interactions.

---