Typically we run biochemical cellular assays that require a high concentration of molecules or cells to get the read out for the assays. With this kit we can watch a single molecule in action, following its binding to a receptor or to monitor its catalytic properties.

This means that in future we can observe the action of a single molecule rather than an ensemble of molecules. Combining the resulting data with the read-outs of multiple molecule scans we can find information that would have been lost by measuring a collection of molecules alone.


We can screen and track molecules at 1,000-fold lower concentrations than previously due to the ultra-sensitivity of the equipment.


We can detect a single molecule's activity which means lower reagent consumption.

A scientist's perspective


Stefan Geschwindner Principal Scientist, Discovery Sciences

Why does AstraZeneca need it?

It enables us to do something we couldn’t do previously (detect a single molecule’s activity). The cost of reagents is also reduced significantly due to single molecule detection.

It provides data across different populations – we can detect heterogeneities and can see information that could be hidden in larger collections of molecules, so we can see how drugs act differently on particular forms of an enzyme or receptor that we wouldn’t be able to see in traditional assays. This could eventually provide an opportunity to further develop our personalised healthcare approach.

Who uses it?

The project started around four years ago with the Chalmers University in Gothenburg using total internal reflection fluorescence or TIRF microscopy. Chalmers University still use the technology as well as other academic labs. We engaged with them to learn about the technology and recognised that there was a huge opportunity for AstraZeneca.

How does the kit help improve the day to day work at AstraZeneca?

It provides a unique opportunity to impact on our drug discovery efforts.

When you start a project you develop assays that allow chemists to view the outputs and understand the action. Most projects reach at some point a tight binding limit with high-affinity binding which means that a new assay needs to be developed. We think this platform could cover all levels of binding affinity from milli-molar right down to femto-molar levels.

In addition, the platform has been recently modified to generate the world-first automated TIRF microscope to meet todays´ screening requirements in drug discovery. This enables scientists to perform accurate kinetic measurements more robustly, involving projects that have been originally deemed unfeasible to tackle with existing biophysical assay technologies.

Has this kit been used in any notable discoveries or activities in AstraZeneca?

We pitched the idea to invest in the microscope and received the equipment in 2015. For the first year we set out to show the impact of the technology in two of our projects. We exceeded this by impacting three different projects:

  • Demonstrating ligand receptor selectivity – This technology has been successful in helping determine the exact affinity of a protein ligand to selected members of a receptor family in order to investigate if a mutated version of the ligand shows the desired receptor selectivity. Previous experiments employing traditional platforms did not display the required data quality and showed large variations. Experimenting with TIRF, we could validate a three-fold increase in selectivity to move the project forward
  • Interaction of nuclear receptors with cofactors – Nuclear receptors can interact with an extensive range (>100) of cofactors when bound to drug molecules. These are essential to achieve the desired biological function and pharmacological response. Interaction profiles with these cofactors can be used to predict a drugs phamacological response. The plate-based nature of the TIRF platform has enabled us to generate profiles for all those cofactors simultaneously, where standard approaches can only generate information for a very limited number (<16) of cofactors or require very expensive setups
  • Measuring kinetic binding data for unstable targets – Traditional surface-based approaches for the determination of kinetic binding data are frequently limited by the instability of the target protein when subjected to these investigations. The TIRF platform has enabled us to measure kinetic binding data for very unstable protein targets and to generate kinetic data of the desired quality to validate a critical project hypothesis. This work is part of a recent publication in Structure.      

Has it won any awards, been mentioned in publications or by notable speakers/experts?

We have published six papers in the last two years, many in high-quality journals together with the academic supervisor. Several more are going through the peer-review process and recently our advances in technology developments have been positively highlighted by some key experts in a Nature Review publication.

A poster presentation at the Liposome Research Days won an award and was followed by an invitation to speak at a drug discovery conference and participate in a round-table discussion. As a result, the organisers have taken up single molecule techniques as a theme for their next conference.

We are also excited by the enormous potential of single molecule techniques in late-stage drug discovery. We are looking at how we can apply this platform in late-stage discovery programmes, in particular with regard to biomarker detection which is currently being explored with the academic collaborator. A prospective view on the great potential of this technology for biosensing applications has been recently published in ACS Sensors.

  Featured publications

Drug discovery at the single molecule level: inhibition-in-solution assay of membrane-reconstituted beta-secretase using single-molecule imaging

Gunnarsson, A.; Snijder, A.; Hicks, J.; Gunnarsson, J.; Hook, F.; Geschwindner, S., Analytical Chemistry 2015, 87 (8), 4100-3.

Affinity Capturing and Surface Enrichment of a Membrane Protein Embedded in a Continuous Supported Lipid Bilayer

Gunnarsson, A.; Simonsson Nystrom, L.; Burazerovic, S.; Gunnarsson, J.; Snijder, A.; Geschwindner, S.; Hook, F., Chemistryopen 2016, 5 (5), 445-449.

Equilibrium-Fluctuation Analysis for Interaction Studies between Natural Ligands and Single G Protein-Coupled Receptors in Native Lipid Vesicles

Wahlsten, O.; Gunnarsson, A.; Nystrom, L. S.; Pace, H.; Geschwindner, S.; Hook, F., Langmuir 2015, 31 (39), 10774-10780

Ligand Binding Mechanism in Steroid Receptors: From Conserved Plasticity to Differential Evolutionary Constraints

Edman, K.; Hosseini, A.; Bjursell, M. K.; Aagaard, A.; Wissler, L.; Gunnarsson, A.; Kaminski, T.; Kohler, C.; Backstrom, S.; Jensen, T. J.; Cavallin, A.; Karlsson, U.; Nilsson, E.; Lecina, D.; Takahashi, R.; Grebner, C.; Geschwindner, S.; Lepisto, M.; Hogner, A. C.; Guallar, V., Structure 2015, 23 (12), 2280-229

Harnessing the Versatility of Optical Biosensors for Target-Based Small-Molecule Drug Discovery

 Kaminski, T.; Gunnarsson, A.; Geschwindner, S., ACS Sensors 2017, 2 (1), 10-15.

Single Molecule Microscopy Reveals an Increased Hyaluronan Diffusion Rate in Synovial Fluid from Knees Affected by Osteoarthritis

Kohlhof, H.; Gravius, S.; Kohl, S.; Ahmad, S. S.; Randau, T.; Schmolders, J.; Rommelspacher, Y.; Friedrich, M.; Kaminski, T. P., Sci. Rep. 2016, 6.