Hydrodynamic effects in fast AFM single molecule force measurements Journal Article


Author(s): Janovjak, Harald; Struckmeier, Jens; Mueller, Daniel J
Article Title: Hydrodynamic effects in fast AFM single molecule force measurements
Affiliation
Abstract: 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 mgrm/s, although for a more complete investigation of the kinetic properties higher speeds are desirable. Above 10 mgrm/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 mgrm/s pulling speed.
Keywords: Atomic force microscopy; Loading rates; Drag force; Dynamic force spectroscopy; Ig27-8
Journal Title: European Biophysics Journal
Volume: 34
Issue 1
ISSN: 0175-7571
Publisher: Springer  
Date Published: 2005-02-01
Start Page: 91
End Page: 96
DOI: 10.1007/s00249-004-0430-3
Open access: no