Measurement of charge distribution in actin bundles by surface potential microscopy

Abstract

Bundles of filamentous actin (F-actin) deposited on a gold-plated surface were concurrently imaged using atomic force microscopy (AFM) and surface potential microscopy (SPM). The surface potential was mapped as a function of tip distance to surface using a constant bias potential. There was an uneven spatial distribution of charges detected by SPM, consistent with the segmented topological features shown by AFM of the actin bundles. SPM analysis showed localized changes in surface potential between the axial and transversal sections of the bundles, which are consistent with nonuniform charge distributions of adsorbed salt ions on F-actin.