Probing the Resolution Limits and Tip Interactions of Atomic Force Microscopy in the Study of Globular Proteins

Steven J. Eppell, Fredy R. Zypman, Roger E. Marchant

Research output: Contribution to journalArticlepeer-review

56 Scopus citations

Abstract

It is suggested that the atomic force microscope, AFM, operating in repulsive force mode with an insulating tip, is sensitive to charged objects on an insulating surface. This sensitivity is shown to significantly affect the topographical images obtained. Theoretical calculations indicate that an electrostatic attractive force as large as 7.7 nN exists between a charged polystyrene sphere on mica and the AFM tip. This result is consistent with the experimental measurements obtained. Globular domains of a blood plasma glycoprotein, von Willebrand factor, were also measured using the AFM to have elliptical cross sections with major axis = 106 (±22) run and minor axis = 81 (±22) nm and heights of 3.4 (±0.83) nm. These domains were modeled with the 14 nm diameter polystyrene spheres. This approach allowed us to measure the instrument response and account for lateral image distortion due to tip size thus enhancing the resolution of our data.

Original languageEnglish
Pages (from-to)2281-2288
Number of pages8
JournalLangmuir
Volume9
Issue number9
DOIs
StatePublished - 1993
Externally publishedYes

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