Imaging an F‐actin structure with noncontact scanning force microscopy

Abstract

F‐actin, a ubiquitous cytoskeletal protein, crucial to cell function and motility, was used as a test sample to compare the resolution limits of non‐contact scanning force microscopy (NCSFM) to that standard of contact scanning force microscopy (SFM). NCSFM probes the surface topography of a sample without direct physical contact between the atomic force microscope cantilever tip and the sample surface, avoiding the type of tip sample damage that one encounters with standard contact SFM. NCSFM images of rhodamine–phalloidin stabilized F‐actin deposited on polished sapphire substrates clearly show filamentous structures on the substrate surface with ∼36 nm periodicity. The polished sapphire substrates present a positive surface charge at pH 7 that complements the negative surface charge of F‐actin during deposition and provides a clean, hard surface. Contact SFM images of the same samples, although showing filaments on the substrate surface, display a lower overall clarity compared to the NCSFM images.