High resolution structural studies of DNA and DNA binding proteins by atomic force microscopy
(AFM) require well-bound samples on suitably flat substrates. Adsorbing the DNA onto a positively charged
supported lipid bilayer has previously been shown to be a potentially effective strategy for structural studies with
AFM. Here, using our home-built frequency-modulation AFM (FM-AFM), we show that these bilayer substrates
are only maximally effective for high resolution AFM when the samples are short, linear DNA, compared with
circular plasmid DNA. We find that, with the former sample, the measured width of the DNA is about 2 nm, the
known DNA diameter, and there is a clear height modulation along the length of the DNA with a periodicity of
about 3.4 nm, in excellent agreement with the known pitch of the double helix. This sample preparation strategy
is expected to enable higher resolution studies of DNA and DNA binding proteins with FM-AFM than that can
presently be achieved.
ZHANG Jin-jin1 (张金金), LVJun-hong1 (吕军鸿), SUN Jie-lin2,3 (孙洁林), HU Jun1 (胡钧),CZAJKOWSKY Daniel M2*, SHEN Yi2* (沈轶)
. Direct Resolution of the Pitch of DNA on Positively Charged Lipid Bilayers by Frequency-Modulation AFM[J]. Journal of Shanghai Jiaotong University(Science), 2014
, 19(5)
: 565
-568
.
DOI: 10.1007/s12204-014-1542-2
[1] Meyer E, Howald L, Ovemey R M, et al.Molecular-resolution images of Langmuir-Blodgett films using atomic force microscopy [J]. Nature, 1991,349: 398-400.
[2] Shao Z, Mou J, Czajkowsky D M, et al. Biological atomic force microscopy: What is achieved and what is needed [J]. Advances in Physics, 1996, 45(1): 1-86.
[3] Dufrene Y F, Pelling A E. Force nanoscopy of cell mechanics and cell adhesion [J]. Nanoscale, 2013, 5:4094-4104.
[4] Ido S, Kimura K, Oyabu N, et al. Beyond the helix pitch: Direct visualization of native DNA in aqueous solution [J]. ACS Nano, 2013, 7(2): 1817-1822.
[5] Yang J, Takeysau K, Shao Z. Atomic force microscopy of DNA molecules [J]. FEBS Letters, 1992,301(2): 173-176.
[6] Mou J, Czajkowsky D M, Zhang Y, et al. High resolution atomic-force microscopy of DNA: The pitch of the double helix [J]. FEBS Letters, 1995, 371(3):279-282.
[7] Wu N, Czajkowsky D M, Zhang J, et al. Molecular threading and tunable molecular recognition on DNA origami nanostructures [J]. Journal of the American Chemical Society, 2013, 135: 12172-12175.
[8] Mou J, Yang J, Shao Z. Tris(hydroxymethyl)aminomethane (C4H11NO3) induced a ripple phase in supported unilamellar phospholipid bilayers [J]. Biochemistry,1994, 33(15): 4439-4443.
[9] Fang Y, Yang J. Two-dimensional condensation of DNA molecules on cationic lipid membranes [J]. Journal of Physical Chemistry B, 1997, 101: 441-449
[10] Asakawa H, Ikegami K, Setou M, et al.Submolecular-scale imaging of a-helices and Cterminal domains of tubulins by frequency modulation atomic force microscopy in liquid [J]. Biophysical Journal,2011, 101: 1270-1276.
[11] Sheikh K H, Jarvis S P. Crystalline hydration structure at the membrane—fluid interface of model lipid rafts indicates a highly reactive boundary region [J].Journal of the American Chemical Society, 2011, 133:18296-18303.
[12] Ido S, Kimiyia H, Kobayashi K, et al. Immunoactive two-dimensional self-assembly of monoclonal antibodies in aqueous solution revealed by atomic force microscopy [J]. Nature Materials, 2014, 13: 264-270.
