MAGNETIC SEPARATION OF DNA AIDED WITH
RECTANGULAR AC ELECTRIC FIELD
Isao Yamamoto*, Shun Ozawa, Taiga Imai and Yasuyuki Shimazaki
Department of Physics, Yokohama National University,
Hodogaya-ku, Yokohama 240-8501, Japan
*corresponding author: isaoy@ynu.ac.jp
Abstract : We have succeeded in actualizing magnetic migration of DNA under the high gradient
magnetic field aided with a rectangular alternative electric field. The migration velocity of DNA depends on
the parameters of the electric field strength, gel concentration and magnetic force field. The magnetic
separation is studied for DNAs with the different magnetic susceptibility.
Keywords : DNA, magnetic separation, gradient magnetic field, electrophoresis, magnetic migration
1. INTRODUCTION
2. EXPERIMENTAL METHOD
DNA is a diamagnetic material and
migrates toward week magnetic field
under high gradient magnetic fields by
the magnetic force. The DNA orients
perpendicular to the magnetic flux.[1]
Also, the motion of the DNA by the
Lorentz force is considerable for the
electrophoretic migration under the
influence of the magnetic field. Therefore,
the DNA migration is influenced by the
homogeneous and/or gradient magnetic
fields. It was reported that the magnetic
migration velocity of DNA was increased
by
applying
AC
electric
field
perpendicular to the magnetic flux.[2] In
this paper the magnetic separation is
studied for two kinds of DNAs, which
have the same electrophoretic velocities
and cannot separates by the ordinary
electrophoresis.
A linear shaped DNA of Ez Load HT
Molecular Ruler with 1 kbp – 15kbp
(Bio-Rad Lab. Inc.) and a circle shaped
plasmid DNA of pCU-18 with 2686 bp
(Takara Bio Co. Ltd.) were used as the
migration materials. The agarose gel
(Wako Chemical) was prepared as a
support media. The DNAs were injected
into wells of the gel surface. The gel was
fixed on the bottom of the electrophoretic
bath with interelectrode distance of 23
mm and filled with the TAE buffer. The
bath was placed in a water jacket on the
vertical bore of a superconducting
magnet (JMTD-13T100, JASTEC) and
temperature of the sample space was kept
at 278 K. The static magnetic field is 9.1
T at the sample position and it
corresponds the magnetic force field of
583 T2/m. The AC electric field was
simultaneously applied for 24 h
perpendicular to the magnetic flux. The
DNA pattern was observed under UV ray
after dyeing with the ethidium bromide
solution for 1 h. The magnetic field effect
on the DNA pattern was studied under
various migration conditions of the
pattern of the electric field, the magnetic
force field strength, the gel concentration,
and the migration duration.
considered the lower and upper bands
corresponds to circle DNA and the linear
DNA.
s t a rt p os it i o n
B
E
3. RESULTS AND DISCUSSION
An example of the linear DNA pattern
after the migration for 24 h was shown in
Fig. 1. The electric voltage was E = 50 V
and the gel concentration was C = 0.5
wt.%. The DNA indicated in an oval was
migrated by 10.3 mm from the start
position along the magnetic flux. This
migration distance corresponded three
times as long as the result with the high
concentrated gel of 0.7 % and three times
for low electrophoretic voltage of 30 V.
The increase of the magnetic migration
velocity was increased with increasing
magnetic force field strength.
DNA
Figure 1. Migraton pattern of DNA under the gradient
magnetic field. E=50V, C=0.5%, t=24h.
s t a rt p os it i o n
DN A
B
E
Figure 2. Magentic separation of DNA.
4. CONCLUSION
The magnetic separation of linear and
circle DNA was tested under the
condition as same as Fig. 1. The two
bands were found in two ovals in Fig. 2.
The ratio of the migration distances for
lower to upper bands was 3:2 along the
magnetic flux. The preliminary results
showed our circle DNA with 2.6 kbp
corresponded to the linear DNA with 1.8
kbp in the electrophoretic velocity. This
ratio of the size is equal to 3:2. The
magnetic force act for DNA is
proportional to the molecular size of
DNA because the volume susceptibility
of two DNAs is thought to be the same.
In the case of Fig. 2, the ratio of 3:2 was
the same between the migration distance
and the DNA size. Therefore, it was
We have succeeded the magnetic
migration to separate the different DNAs
with the same electrophoretic velocity. It
was preformed with the aid of AC
electric field.
ACKNOWLEDGEMENT
This work was partially supported by Grants-inAided for Scientific Research, MEXT, Japan (No.
20560044).
REFERENCES
[1] Morii, N. et al, 2005, Bio Industry 5, pp. 32-40.
[2] Ozawa, S. et al, 2011, Jan. J. Appl. Phys 50, 070212.