
23
Sorting of PCR positive dPCR droplets
In this step, the dPCR droplets containing your DNA molecules of interest are separated from the negative droplets and
the DNA of interest is enriched. Depending on the input, you will get few DNA molecules after sorting, too low an
amount to quantify directly. To amplify the sorted DNA, please continue with the general amplification dMDA kit
developed for the Xdrop™ technology. Please refer to the
Xdrop
TM
Manual Droplet MDA (dMDA).
1.
Confirm that the sort settings for your cell sorter are correct. Check that the side streams are centered on the
collection tube.
2.
Set the gates as detailed above for flow cytometry analysis (Fig. 4.3), taking care to draw a strict gate around
the population of interest. NB: be aware of potential drift in fluorescence over time and be prepared to move
the sorting gate during the sort if required.
3.
Add 15 μl of molecular grade H
2
O into the bottom of a 1,5 ml low binding collection tube and place the
collection tube in the appropriate holder for collection in the cell sorter instrument.
4.
Start sorting the positive population into the collection tube containing H
2
O. Remember to acquire data during
the sort for your records.
5.
After sorting keep the tube with sorted droplets at 4°C.
6.
Continue immediately to dMDA if applicable. NB: Do not store sorted dPCR droplets longer than a few hours at
4°C as this will lead to loss of material and DNA integrity.
To calculate the enrichment post-dMDA, please refer to the
Xdrop
TM
Manual Droplet MDA
and use the online tool for
calculating the enrichment at
samplix.com