Scanning Tunneling Microscopy Studies on Xanthan Gum
The application of the scanning tunneling microscope (STM) to imaging biological molecules has generated much interest over recent years. Research has mainly concentrated on obtaining images of DNA, proteins and small organic molecules. However, the work we present concerns polysaccharides, specifically xanthan gum, commonly used in the food and oil industries. We have employed high-resolution metallic shadowing to overcome some of the problems associated with imaging biological molecules by STM, such as tip-sample interaction effects and lack of conduction. The images displayed demonstrate the ability of the STM to image replicas of discrete polysaccharide molecules. We directly correlate and compare these results with electron micrographs of similarly prepared molecules. In addition, the effect of different sample deposition techniques and substrates on the resultant images of xanthan gum is demonstrated. We discuss the implications for sample preparation procedures for future STM studies on biological molecules.
KeywordsScan Tunneling Microscope Scan Tunneling Microscope Image Highly Orient Pyrolytic Graphite Spray Deposition Mica Substrate
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- 2.C.J. Roberts, M. Sekowski, M.C. Davies, D.E. Jackson, M.R. Price and S.J.B. Tendler, Topographical investigations of human ovarian carcinoma polymorphic epithelial Mucin, Biochem. J. 283, 181–185 (1992).Google Scholar
- 4.M.C. Davies, D.E. Jackson, K.M. Kreusel, C.J. Roberts, S.J.B. Tendler, M.J. Wilkins and P.M. Williams, Polymer surfaces III scanning probe microscopy: current issues in the analysis of polymeric biomolecules, Polymer Surfaces II:227–247, J. Feast, ed., Wiley.Google Scholar
- 6.T.E. Wilson, M.N. Murray, D.F. Ogletree, M.D. Bednarski, C.R. Cantor, and M.B. Salmeron, Scanning tunneling microscopy at high gap resistances and on chemically modified silicon surfaces, J. Vac. Sci. Technol. B9, 1171–1176 (1991).Google Scholar
- 9.T. Harada, Y. Kanzawa, K. Kanenaga, A. Koreeda, and A. Harada, Electron microscopic studies on the ultrastructure of curdlan and other polysaccharides in gels used in foods, Food Structure 10, 1–18 (1991).Google Scholar
- 10.G.J. Leggett, M.J. Wilkins, M.C. Davies, D.E. Jackson, C.J. Roberts and S.J.B. Tendler, A scanning tunneling microscopy and transmission electron microscopy study of poly(ethylene oxide) films, Langmuir in press.Google Scholar
- 13.B.T. Stokke and A. Elgsæter, Electron microscopy of carbohydrate polymers, “Advances in Carbohydrate Analysis,” Vol.], 195–247 JAI Press, Ltd. (1991).Google Scholar