Plasmid DNA Purification
MACHEREY-NAGEL – 01/2008/ Rev. 04
65
Problem
Possible cause and suggestions
Nucleic acid
pellet is
opaque or
white instead
of clear and
glassy
Co-precipitation of salt
•
Check isopropanol purity, and perform precipitation at room
temperature (20-25°C) but centrifuge at 4°C. Do not let the elu-
ate drip from the column into isopropanol but add isopropanol to
the final eluate and mix immediately.
•
Try resuspending the pellet in Buffer WASH, and reload onto the
same NucleoBond
®
Xtra column. Wash the column several
times with Buffer WASH before loading.
Nucleic acid
pellet does not
resuspend in
buffer
Pellet was over-dried
•
Try to dissolve at higher temperatures for a longer period of time
(e.g. 2 h at 37°C or overnight at RT), preferably under constant
spinning (3D-shaker).
Co-precipitation of salt or residual alcohol
•
Wash the pellet again with 70% ethanol, or increase the recon-
stitution buffer volume.
No or low
plasmid DNA
yield after
NucleoBond
®
Finalizer pre-
cipitation
Already no or low plasmid DNA after elution from the NucleoBond
®
Xtra column
•
Refer to detailed trouble shooting “No or low plasmid DNA yield”.
Dead volume too high
•
Especially when you aim for high concentration you need to
elute in small volumes. But naturally you will lose parts of your
eluate in the syringe and on the NucleoBond
®
Finalizer. To
minimize these losses in the second elution step, try to transfer
even the last droplet from the syringe to the NucleoBond
®
Final-
izer, e.g. by tapping the NucleoBond
®
Finalizer and syringe onto
the bench top. Then fill the syringe with air and press forcefully
the last droplets out of the NucleoBond
®
Finalizer. Repeat this
step several times. You might have to practice this procedure
several times to achieve optimal results. An acceptable dead
volume is smaller than 30 µl with NucleoBond
®
Finalizer and
60 µl with NucleoBond
®
Finalizer Large.
Elution volume too small
•
Since there are dead volumes of about 30 µl (NucleoBond
®
Fi-
nalizer) and 60 µl (NucleoBond
®
Finalizer Large), reasonable
elution volumes start with 200 µl (NucleoBond
®
Finalizer) and
400 µl (NucleoBond
®
Finalizer Large) respectively. Furthermore,
smaller volumes are insufficient to wet the entire membrane and
will drastically decrease your yield. Refer to section 4.11, Table
4 and 5 to estimate the recovery that can be expected depend-
ing on elution buffer volume.