Hydrodynamic effects in fast AFM single-molecule force measurements

Harald Janovjak, Jens Struckmeier, Daniel J. Müller

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96 Citations (Scopus)


Atomic force microscopy (AFM) allows the critical forces that unfold single proteins and rupture individual receptor-ligand bonds to be measured. To derive the shape of the energy landscape, the dynamic strength of the system is probed at different force loading rates. This is usually achieved by varying the pulling speed between a few nm/s and a few μm/s, although for a more complete investigation of the kinetic properties higher speeds are desirable. Above 10 μm/s, the hydrodynamic drag force acting on the AFM cantilever reaches the same order of magnitude as the molecular forces. This has limited the maximum pulling speed in AFM single-molecule force spectroscopy experiments. Here, we present an approach for considering these hydrodynamic effects, thereby allowing a correct evaluation of AFM force measurements recorded over an extended range of pulling speeds (and thus loading rates). To support and illustrate our theoretical considerations, we experimentally evaluated the mechanical unfolding of a multi-domain protein recorded at 30 μm/s pulling speed.

Original languageEnglish
Pages (from-to)91-96
Number of pages6
JournalEuropean Biophysics Journal
Issue number1
Publication statusPublished - Feb 2005
Externally publishedYes


  • Atomic force microscopy
  • Drag force
  • Dynamic force spectroscopy
  • Ig27-8
  • Loading rates

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