title: Molecular-scale quantitative charge density measurement of biological molecule by frequency modulation atomic force microscopy in aqueous solutions.
abstract: Surface charge distributions on biological molecules in aqueous solutions are essential for the interactions between biomolecules, such as DNA condensation, antibody-antigen interactions, and enzyme reactions. There has been a significant demand for a molecular-scale charge density measurement technique for better understanding such interactions. In this paper, we present the local electric double layer (EDL) force measurements on DNA molecules in aqueous solutions using frequency modulation atomic force microscopy (FM-AFM) with a three-dimensional force mapping technique. The EDL forces measured in a 100 mM KCl solution well agreed with the theoretical EDL forces calculated using reasonable parameters, suggesting that FM-AFM can be used for molecular-scale quantitative charge density measurements on biological molecules especially in a highly concentrated electrolyte.
authors.affiliation: Department of Electronic Science and Engineering, Kyoto University, Katsura, Nishikyo, Kyoto 615-8510, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Umeda
authors.forename: Kei
authors.initials: K
authors.lastname: Kobayashi
authors.forename: Noriaki
authors.initials: N
authors.lastname: Oyabu
authors.forename: Kazumi
authors.initials: K
authors.lastname: Matsushige
authors.forename: Hirofumi
authors.initials: H
authors.lastname: Yamada
mesh_terms: D004247:DNA / Q000737:chemistry*; D004560:Electricity; D018625:Microscopy, Atomic Force; D013499:Surface Properties; D014867:Water / Q000737:chemistry
chemical_list: D014867:Water; D004247:DNA