Japanese scientists have created a propeller-shaped molecule that could prove to be a useful sensor of biological molecules such as neurotransmitters.

Fig. 1: The propeller-lie molecular sensor can latch onto chiral biomolecules.

The structure of the molecular sensor produced by the researchers (Fig. 1) is based on benzene rings, each of which is made up of six carbon atoms arranged into a hexagon.1 Four of the flat benzene rings are arranged around a central core to form a terephthalamide structure. The rings can either be angled in the same direction — like the blades of a propeller — or at opposing angles. The ‘screw’ of the propeller's blades can similarly be set either clockwise or anticlockwise, mirror-image (chiral) forms just like our left and right hands.

The propeller carries two amide chemical groups that can latch on to chiral biomolecules. The screw of the blades determines how well the biomolecule fits the propeller — just as a right hand fits snugly into a handshake with another right hand, but does not fit so well with an opposing left hand.

The researchers could assess how well the molecules matched up using a technique called circular dichroism (CD) spectroscopy, which measures how well circularly polarized light (twisting clockwise or anticlockwise as it travels) is absorbed by the molecule.

This means that the propeller can reveal the chirality of a biomolecule. The researchers demonstrated the propeller's function by sensing the chirality of the neurotransmitter (–)-phenylephrine. “As far as we know, our molecules are the first propellers to achieve chirality sensing,” says Takanori Suzuki of Hokkaido University, who led the research team.

The size of the CD signal also provides extra information about the shape of the biomolecule, and the propeller can differentiate between a single biomolecule with two binding points and two biomolecules with one binding point each.

Suzuki says that the propeller could be modified so that binding to one molecule then triggers further actions, such as enabling it to bind to a second molecule or activating a catalyst. For now, the team are trying to improve the sensitivity of the system, and hope to add a fluorescent group to their propeller to produce a visible flash when it binds to a biomolecule.