By Meghan Bialt-DeCelie ’19

Single molecule detection techniques are used to understand the behaviors of a specific biological molecule and have applications in medical and pharmacological research. This can be critical for understanding how an individual biological molecule, such as a specific protein, functions, as well as its role in a biological pathway.

Researchers led by Stuart Lindsay, PhD from Arizona State University found high electronic conductance in the human protein integrin using a single molecule detection technique called Scanning Tunnel Microscopy (STM). In this type of microscopy, a single protein molecule is held at a junction nanometers wide, called a nanopore, between electrodes. They attached the ligand RGD which specifically binds human integrin to the electrodes. When the protein bound to the ligand, they found that the protein conducted about a nanoamp of current, a relatively high amount, between the electrodes. The integrin was not always in this conductive state. This only occurred when the electrodes were providing a threshold of a few tenths of a volt across a distance of about 5 nm. The electrical signals were also influenced by the ligand that the protein bound to; a more specific ligand, a ligand that bound more tightly to the protein, improved these conductive properties.

The use of STM to look at conductance thresholds of proteins can pave the way for studying the electrochemical properties of single biological molecules and providing a clearer understanding of a molecule’s function in a biological system.

References:

1. S. Lindsay, et al. Observation of giant conductance fluctuations in a protein. Nano Futures 1, (2017). doi: 10.10882399-1984/aa8f91.
2. Image retrieved from: https://en.wikipedia.org/wiki/Nanopore_sequencing