Graphene boosts single-molecule imaging


Rebecca Pool

Wednesday, September 4, 2019 - 14:45
Image (left) of single molecules on a graphene sheet, expected image (right).
Germany-based researchers have developed a novel technique that takes advantage of the unusual properties of graphene to electromagnetically interact with fluorescing molecules.
Pioneered by Professor Jörg Enderlein, Head of the Third Institute of Physics (Biophysics) at the University of Göttingen, 'graphene-based metal-induced energy transfer for sub-nanometre optical localization' allows scientists to optically measure ångström distances with high accuracy and reproducibility.
Enderlein and his team used the method to optically measure the thickness of lipid bilayers.
The researchers used a single sheet of graphene, just one atom thick, to modulate the emission of fluorescent molecules that came close to the graphene sheet.
The excellent optical transparency of graphene and its capability to modulate through space the molecules’ emission made it an extremely sensitive tool for measuring the distance of single molecules from the graphene sheet.
A dye labelled membrane seen under polarised light (arrow). This shows that molecules are oriented along the perimeter of the membrane.
According to the researchers the method can resolve distance changes of around 1 ångström.
They demonstrated this by depositing single molecules above a graphene layer and then determining the distance by monitoring and evaluating light emission.
As they say, this graphene-induced modulation of molecular light emission provides an extremely sensitive and precise “ruler” for determining single molecule positions in space.
The researchers went on to measure the thickness of single lipid bilayers, comprising only two layers of fatty acid chain molecules and with a thickness of only a few nanometres.
“Our method has enormous potential for super-resolution microscopy because it allows us to localise single molecules with nanometre resolution not only laterally (as with earlier methods) but also with similar accuracy along the third direction, which enables true 3D optical imaging on the length scale of macromolecules,” says Arindam Ghosh from the University of Göttingen.
 “This will be a powerful tool with numerous applications to resolve distances with sub-nanometre accuracy in individual molecules, molecular complexes, or small cellular organelles,” adds Enderlein.
Research is published in Nature Photonics.
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