Thread by @paoloactis

A Tweetorial about our recent work @acsnano on polymer-electrolyte nanopore. Super collaboration between @uarkfulbright @AstburyCentre @BraggRoyceLeeds brilliantly delivered by @Chalmazers @Fabio_Marcuccio @dsoulias
pubs.acs.org/doi/10.1021/ac…

About 2 years agom we published @NanoLetters the discovery that 50% PEG generates a very large signal-to-noise enhancement in a nanopore. We attributed this effect to the macromolecular crowding properties of PEG…but is there more to it?
pubs.acs.org/doi/full/10.10…

Recently @SConfederat @Gayathr06377645 and Ila have shown @BiophysJ that this approach enables the fingerprinting of supramolecular DNA nanostructures Sam will be presenting this work #SMPS3 if you want to know more! @cees_dekker @ChirlminJoo_Lab
cell.com/biophysj/fullt…

PEG comes in a lot of shapes and sizes and we found that PEG molecular weight influences the signal enhancement, and PEG 35K works best. We have not checked longer PEGs and we do not quite know yet what the mechanism leading to this effect (but more on this later)

We only add PEG to the trans chamber and the single molecule signals (of a model 4.8Kb dsDNA) are independent of the buffer used in the cis chamber. If you change the electrolyte you also modify the signal (which is not new, as LiCL is widely used in nanopore sensing)

But our system is different!!! No matter what electrolyte we use to dilute our analyte, the signal (to a certain extent) is only determined by the electrolyte used in the trans chamber so DNA counterions can't be solely responsible…so what is driving the signal?

PEG has been widely used a model analyte in biological nanopores (@BehrendsLab @joewfrob ) and its ability to bind cations is well known also in the field of Li-ion batteries. We screened a range of electrolyte and discovered that CsBr leads to the largest signal enhancement

It seems that the amplitude of the single molecule signals correlate to the ability of PEG to chelate ion using the electrolyte lattice energy as a proxy (nitty gritty details in the paper)
pubs.acs.org/doi/10.1021/ac…

It looks like the ability of PEG to interact with ions, rather than its macromolecular crowding property, is responsible for driving the signal enhancement. We have developed a multiphysics model to explain this effect in @biorxivpreprint @MEdwardsLab
biorxiv.org/content/10.110…

One consequence of the enhanced single molecule signals is that you can switch your low-pass filter off and still detect events. Drop us a line if you have any cool ideas about a collaboration! @FreedmanLab_UCR @sciSonja @NanoporeHolic

You can study viral RNA molecules under physiological conditions. Thanks @Tuplin_Lab ! The buffer you dilute your analyte in does not affect the signal so you can keep your molecules happy in PBS and use PEG+CsBr in the trans chamber to boost your signal.

And we can also probe RNA conformations after thermodynamic refolding to complement some of the exciting work done by @WanunuLab and the recent gem in @NatureChemistry by @FilipBoskovic12 @KeyserLab

We still do not know if this signal enhancements works on solid state nanopores other than nanopipettes and we do not know what happens to the analyte when it gets into 50% PEG… there could be some interesting physics to study there

We are particularly keen to link up with #batterytwitter #batterychat to test other solid electrolytes and learn more about polymer-electrolyte interactions. Any comments/ideas/critiques, just drop us a line !

A big big thanks @SENTINEL_ITN @MSCActions @EPSRC @royalsociety @The_MRC for supporting this work and to @EdelResearch for sharing his amazing MatLab script!!!