Resolution and Limitations in Biological Applications of Atomic Force Microscopy
Atomic force microscopy (AFM) has been applied to image DNA and a membrane protein: cholera toxin. By use of the Kleinschmidt method, DNA molecules were picked up on carbon-coated mica surfaces and imaged by AFM in air and in organic solvents. The resolution was found to be closely related to the adhesion force and a resolution of 3–6 nm was routinely obtained when the adhesion force was below 3 nN. The role of the adhesion force, the tip condition and the specimen preparation on resolution and imaging quality will be discussed. Polymerized diacetylene phosphatidylcholine (DAPC) bilayers provide a relatively stable matrix for studying membrane proteins. When cholera toxin (complete or B-subunit oligomer) was bound to mixed bilayers of DAPC and the receptor glycolipid GM1, the subunit structure was well resolved by AFM in buffer, without crystallization. The resolution was better than 2 nm with excellent reproducibility for a probe force of 0.3–0.5 nN. These results show that individual biomacromolecules under native conditions can be imaged by AFM with high spatial resolution.
KeywordsAdhesion Force Cholera Toxin High Resolution Image Lateral Resolution Probe Force
Unable to display preview. Download preview PDF.
- 5.H.-J. Butt, E.K. Wolff, S.A.C. Gould, B.D. Northern, C.M. Peterson, and P.K. Hansma, Imaging cells with the atomic force microscope, J. Struct. Biol. 105, 54–61 (1990).Google Scholar
- 6.K.L. Dorrington, The theory of viscoelasticity in biomaterials, in: “The Mechanical Properties of Biological Materials,” Cambridge University Press, Cambridge (1979).Google Scholar
- 7.D.M. Gill, Mechanism of action of cholera toxin, Adv. Cyc. Nucleo. Res. 8, 85–118 (1977).Google Scholar
- 9.W. IIaberle, J.K.H. Horber, F. Ohnesorge, D.P.E. Smith, G. Binnig, In situ investigation of single living cells infected by viruses, Ultramicroscopy 42–44, 1161–1167 (1992).Google Scholar
- 15.J. Holmgren, Actions of cholera toxin and the prevention and treatment of cholera, Nature 292, 413417 (1981).Google Scholar
- 17.Y.L. Lyubchenko, A.A. Gall, L.S. Shlyakhtenko, R.E. Harrington, and S.M. Lindsay, Atomic force microscopy imaging of large double stranded DNA molecules, Biophys. J. 61, A149 (1992).Google Scholar
- 19.Y.I,. Lyubchenko, P.I. Oden, D. Lampner, S.M. Lindsay and K.A. Dunker, Atomic force microscopy of DNA and bacteriophage in air, water and propanol: the role of adhesion forces, Nucl. Acids Res. in press.Google Scholar
- 21.J. Mou, J. Yang, and Z. Shao, An optical detection low temperature atomic force microscope at ambient pressure for biological research, Rev. Sci. Instrum. in press.Google Scholar
- H.O. Ribi, D.S. Ludwig, K.L. Mercer, G.K. Schoolnik, R.D. Kornberg, Three-dimensional structure of cholera toxin penetrating a lipid membrane, Science 239, 1272–1276 (1988).Google Scholar
- 27.D. Sarid, “Scanning Force Microscopy,” Oxford University Press, Oxford, New York (1990).Google Scholar
- 31.J. Yang and Z. Shao, The effect of probe force on the resolution of atomic force microscopy of DNA. Ultramicroscopy, in press.Google Scholar
- 32.J. Yang, A.V. Somlyo, M.K. Reedy, K. Takeyasu, L.K. Tamm, M. Allietta, T.W. Tillack, and Z. Shao, Biological applications of AFM, in: “Proc. 50th EMSA Annual Meeting,” Boston, MA., 1138–1139 (1992).Google Scholar