NucleoBond
®
Xtra Midi/Maxi -
English
MACHEREY-NAGEL – 01/2008/ Rev. 04
26
Midi
Maxi
7
Neutralization
(Buffer NEU)
Add
Neutralization Buffer NEU
to the suspension and immediately mix the lysate
gently by
inverting
the tube
10-15 times
.
Do not vortex.
The flask or tube used for this step should not be filled more than two thirds to
allow homogeneous mixing. Make sure to neutralize completely to precipitate all
the protein and chromosomal DNA. The lysate should turn from a slimy, viscous
consistency to a low viscosity, homogeneous suspension of an off-white floccu-
late.
Immediately proceed with step 8.
An incubation of the lysate is not necessary
.
Note: Increase NEU buffer volume proportionally if more than the recommended cell
mass is used (see section 4.6 for information on optimal cell lysis).
8 ml
12 ml
8
Clarification and loading
Make sure to have a homogeneous suspension of the precipitate by
inverting the
tube 3 times
directly before applying the lysate to the equilibrated NucleoBond
®
Xtra column filter to avoid clogging of the filter.
The lysate is simultaneously cleared and loaded onto the column. Refill the filter if
more lysate has to be loaded than the filter is able to hold. Allow the column to
empty by gravity flow.
Alternative:
The precipitate can be removed by centrifugation at
5,000 x
g
for at
least 10 min, e.g. if more than double the recommended cell mass was used. If
the supernatant still contains suspended matter transfer it to a new tube and re-
peat the centrifugation, preferably at higher speed, or apply the lysate to the
equilibrated NucleoBond
®
Xtra column filter.
This clarification step is extremely important since residual precipitate may clog
the NucleoBond
®
Xtra column. To load the column you can either apply the
cleared lysate to the equilibrated filter or remove the unused filter beforehand. Al-
low the column to empty by gravity flow.
Note: You may want to save all or part of the flow-through for analysis (see section 8.1).