Fluid Operation
Binding DNA to Mica
Rev. B
MultiMode SPM Instruction Manual
145
8.7
Binding DNA to Mica
8.7.1 DNA Binding Theory
DNA and mica are both negatively charged, and so it is necessary to modify the mica surface or the
DNA counter ion to allow binding. The counterion method is done by adsorbing the DNA onto the
mica in the presence of a divalent (+2 charged) ion, like Ni
+2
. The divalent ion will serve as a
counterion on the negatively charged DNA backbone and will also provide additional charge to
bind the mica. This is shown schematically in
.
Figure 8.7a
Negatively charged DNA may be bound to negatively charged mica in the presence of divalent
counterions, such as Ni
+2
.
8.7.2 DNA Binding Procedure
The following procedure is adapted from these sources:
•
Dunlap, D.D., A. Maggi, M.R. Soria & L. Monaco (1997) “Nanoscopic Structure of
DNA Condensed for Gene Delivery.”
Nucl. Acids Res.
25
, 3095.
•
Kasas, S., N.H. Thomson, B.L. Smith, H.G. Hasma, X. Zhu, M. Guthold, C.
Bustamante, E.T. Kool, M. Kashlev & P.K. Hasma (1997) “
Escherichia coli
RNA
polymerase activity observed using atomic force microscopy.”
Biochemistry
36
, 461.
•
Lyubchenko, Y.L. & L.S. Shlyakhtenko (1997) “Direct Visualization of Supercoiled
DNA
in situ
with Atomic Force Microscopy.”
Proc. Natl. Acad. Sci. USA
94
, 496.
Many other references regarding DNA imaging are listed in the Digital Instruments Biological
Applications Bibliography; call Veeco for a copy.
- - - - - - - - - - -
Mica
++ ++ ++ ++ ++ ++ ++ ++ +
- - - - - - - - - -
DNA molecule
Ni+2 or Mg+2 ions
Buffer solution
