The X-ray crystal structure of a 192-atom-loop molecular 819 knot featuring iron ions (purple), oxygen atoms (red), nitrogen atoms (dark blue), carbon atoms (shown in metallic grey, with one of the building blocks shown in light blue) and a single chloride ion (green) at the center of the structure(Credit: Robert W. McGregor (www.mcgregorfineart.com))
Untangling a tightly wound knot can be a difficult task when dealing with shoelaces, but untangling a molecular knot produced by scientists at the University of Manchester would likely bring a whole new level of frustration. Measuring roughly 20 nanometers long, its creators claim it is the most tightly knotted physical structure ever known and could lead to the development of new advanced materials.
The knot in question contains eight crossings in a 192-atom closed loop of multiple molecular strands and was "tied" using a self-assembly technique whereby the molecular strands were woven around metal ions. Professor David Leigh from Manchester's School of Chemistry says this forms crossing points at the right spots, similar to knitting. To close the loop, a chemical catalyst was used to fuse the ends of the strands together and complete the knot.
"The eight-crossings molecular knot is the most complex regular woven molecule yet made by scientists," says Prof. Leigh.
The team says the ability to form different types of molecular knots will allow them to examine how such knotting affects the strength and elasticity or materials and opens up the potential to weave polymer strands and create new types of super-strong and flexible materials.
"Tying knots is a similar process to weaving so the techniques being developed to tie knots in molecules should also be applicable to the weaving of molecular strands," says Prof Leigh. "For example, bullet-proof vests and body armor are made of kevlar, a plastic that consists of rigid molecular rods aligned in a parallel structure – however, interweaving polymer strands have the potential to create much tougher, lighter and more flexible materials in the same way that weaving threads does in our everyday world."
The team's research appears in the journal Science and the structure of the molecular knot can be seen in the video below.
Source: University of Manchester