The tubular structure is based on the stacking of cyclic peptides, which provide a tube with a channel of around 1nm (around one millionth of a mm)—the right size to allow small molecules and ions to pass through. (Credit: public-sector-lists.com/Flickr)

Tiny ‘Lego’ blocks build two-faced nanotubes

Using a process similar to molecular Lego, scientists have made “Janus nanotubes”—very small tubes with two distinct sides. They’re named for the Roman god Janus, who is usually depicted as having two faces, since he looks to the future and to the past.

The tubular structure is based on the stacking of cyclic peptides, which provide a tube with a channel of around 1nm (around one millionth of a mm)—the right size to allow small molecules and ions to pass through.

Attached to each of the cyclic peptides are two different types of polymers, which tend to de-mix and form a shell for the tube with two faces.

The faces provide two remarkable properties.

In the solid state, they could be used to make solid state membranes which can act as molecular “sieves” to separate liquids and gases one molecule at a time—a property that shows promise for applications such as water purification, water desalination, and gas storage.

In a solution, they assemble in lipids bilayers, the structures that forms the membrane of cells, and organize themselves to form pores that allow the passage of molecules of precise sizes. In this state they could be used for the development of new drug systems, by controlling the transportation of small molecules or ions inside cells.

Versatile performers

“There is an extraordinary amount of activity inside the body to move the right chemicals in the right amounts both into and out of cells,” says Sebastien Perrier, professor at the University of Warwick.

“Much of this work is done by channel proteins, for example in our nervous system where they modulate electrical signals by gating the flow of ions across the cell membrane,” he says.

The findings are published in the journal Nature Communications.

“As ion channels are a key component of a wide variety of biological process, for example in cardiac, skeletal, and muscle contraction, T-cell activation and pancreatic beta-cell insulin release, they are a frequent target in the search for new drugs.” Perrier says.

“Our work has created a new type of material—nanotubes—which can be used to replace these channel processes and can be controlled with a much higher level of accuracy than natural channel proteins.

“Through a process of molecular engineering—a bit like molecular Lego—we have assembled the nanotubes from two types of building blocks—cyclic peptides and polymers.

“Janus nanotubes are a versatile platform for the design of exciting materials which have a wide range of application, from membranes—for instance for the purification of water—to therapeutic uses, including the development of new drug systems.”

Source: University of Warwick

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