title: Methods for imaging DNA in liquid with lateral molecular-force microscopy.
abstract: Shear force microscopy is not normally associated with the imaging of biomolecules in a liquid environment. Here we show that the recently developed scattered evanescent wave (SEW) detection system, combined with custom-designed vertically oriented cantilevers (VOCs), can reliably produce true non-contact images in liquid of DNA molecules. The range of cantilever spring constants for successful shear force imaging was experimentally identified between 0.05 and 0.09 N m(-1). Images of λ-DNA adsorbed on mica in distilled water were obtained at scan rates of 8000 pixels s(-1). A new constant-height force mapping mode for VOCs is also presented. This method is shown to control the vertical position of the tip in the sample plane with better than 1 nm accuracy. The force mode is demonstrated by mapping the shear force above λ-DNA molecules adsorbed on mica in a liquid environment at different tip-sample separations.
authors.affiliation: H H Wills Physics Laboratory, University of Bristol, Tyndall Avenue, Bristol, UK. Robert.Harniman@bristol.ac.uk
authors.forename: R L
authors.initials: RL
authors.lastname: Harniman
authors.forename: J A
authors.initials: JA
authors.lastname: Vicary
authors.forename: J K H
authors.initials: JK
authors.lastname: Hörber
authors.forename: L M
authors.initials: LM
authors.lastname: Picco
authors.forename: M J
authors.initials: MJ
authors.lastname: Miles
authors.forename: M
authors.initials: M
authors.lastname: Antognozzi
mesh_terms: D004279:DNA, Viral / Q000737:chemistry* / Q000648:ultrastructure*; D004867:Equipment Design; D019544:Equipment Failure Analysis; D044085:Microfluidics / Q000295:instrumentation*; D018625:Microscopy, Atomic Force / Q000295:instrumentation*; D012996:Solutions / Q000737:chemistry*; D020349:Surface Plasmon Resonance / Q000295:instrumentation*
chemical_list: D004279:DNA, Viral; D012996:Solutions