Depixus
Writing about all the craziness around Nanobiosym reminded me of Depixus. One of Nanobiosym’s ideas (monitoring single molecules tethered to beads) is similar to what Depixus have going on.
As it’s been several years since I last looked at them, I figured it would be interesting to checkin!
Depixus always seemed pretty neat, a DNA strand attached to a surface and a magnetic bead. By pulling on the bead, you can zip and unzip the DNA. The original idea was to use this for DNA sequencing:
Ligate complementary sequences, detect by changes in the unzipping. This could be monitored optically using what I imagine is a fairly simple optical system:
There are clear issues1 with using this for DNA sequencing, particularly with ligation. It may have been possible to resolve these but instead they pivoted toward a more general molecular interaction platform:
The one way of using this platform appears to be tethering a couple of proteins to a DNA backbone. Then applying force to pull the strand and break the binding between the proteins. So you can measure binding strength. You can also do things, like looking at transient binding etc.
There are a few publications on their site, the latest is from September 2024 using a prototype instrument. But it’s not using the platform in the embodiment described above. In this publication they attach an RNA Riboswitch (PreQ1) to a bead and the flowcell and pull on it to unfold it. By ramping the applied force they can get it to fold/unfold and monitor the effect of various ligands.
It all seems very neat. But I’m not clear on the market size for such an instrument…