The left: Image of single molecules on the graphene sheet. Such images allow scientists to determine the position and orientation for each molecule. Comparison with the expected image (right) shows excellent agreement.Image Credit: University of Göttingen
Researchers at the University of Göttingen have put to good use the extraordinarily unique properties of graphene to electromagnetically interact with fluorescing (light-emitting) molecules. This technique enables scientists to measure exceptionally small distances in the order of 1 ångström (one ten-billionth of a meter) with great precision.
This new method allows for a ten-fold improvement in optical resolution and enabled the researchers to accurately measure the thickness of lipid bilayers, the very stuff that is the fabric and make-up of the membranes all living cells.
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 three-dimensional optical imaging on the length scale of macromolecules.
Arindam Ghosh, First author of the paper
The team at the University of Göttingen, led by Professor Enderlin, modulated the emission of the fluorescent light-emitting molecules using just a single sheet of graphene – just one atom thick (0.34 nm). Due to the fact graphene has an outstanding optical transparency – coupled with its capability and to modulate through space the molecules’ emission – makes it a particularly effective and sensitive tool for measuring the distance of single molecules from the graphene sheet.
This means that the even the slightest of changes in distance (about 1 ångström, the diameter of a single atom) can be resolved. To demonstrate this, the research team deposited single molecules above a graphene layer which allowed them to record their distance by careful analysis of the light emission.
Ultimately, this technique of graphene-induced modulation of molecular light emission proves to be a ‘ruler’ that can determine single molecule positions in space with unparalleled precision. The team utilized this method to measure and record the thickness of single lipid bilayers comprised of two layers of fatty acid chain molecules with an overall thickness of only a few nanometers (1 billionth of a meter). The images this technique is able to produce allows scientists to determine the position and orientation for individual molecules.
“This will be a powerful tool with numerous applications to resolve distances with sub-nanometer accuracy in individual molecules, molecular complexes, or small cellular organelles,” adds Professor Jörg Enderlein, the publication’s corresponding author and head of the Third Institute of Physics (Biophysics) where the work took place.
One of the biggest challenges faced was the application of this technology in single-molecule localization super-microscopy (SMLM) and how to achieve super resolution along the third dimension. The introduction of graphene into this new methodology increases the localization accuracy and therefore resolves the challenges scientists had previously been facing.
Therefore, what the team have achieved opens the door to significant progression in the science behind single-molecule fluorescence imaging providing a boost to many fields of research, from fundamental physics to the life sciences.
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