Biology relies on topology for the function of many of its most intricate molecular machines. For example, the capsid of the HK97 bactereophage virus (shown below) consists of interwoven protein rings with the topology of chain mail! This capsid's interlocked, woven-together circular proteins provide a robust protection for the DNA within.
The topology of ATP Synthase, analogous to a rod poking through a sheet, is also essential to its function. The flow of protons from one side of the sheet (lipid bilayer) to the other is coupled to rotary motion, which in turn generates ATP from ADP and phosphate.
We have gained a degree of control over the topology of certain product structures, as detailed in "Helicate, macrocycle or catenate: dynamic topological control over subcomponent self-assembly" Chem. Eur. J. 2006, 12, 4069-4076. The short, flexible aliphatic diamine subcomponent shown below results in the formation of the macrocycle shown at right as the unique self-assembled product. A longer diamine, which contains rigid phenylene segments, cannot easily link up into a macrocyclic topology around a dicopper double-helicate core, but it is predisposed to generate the catenane shown at left: an assembly of two macrocycles, each threaded through the other around the two copper template ions.
Our efforts in this field are currently focused on synthesising structures with yet more complex topologies, such as knots and the rather exotic structure shown below. As observed in biological systems, complex topologies can lead to complex functions.
