Atomic force microscopy surface forces

Experimentally, rupture forces in biological systems can be measured with atomic force microscopy, surface force apparatus, optical tweezers, or the biomembrane force probe technique. Each of these methods operates on different time.scales and gives additional insights into the dynamics strength of biological bonds (see Ref. 75). Since none of these methods yields details on the atomic level, this is a nice application for molecular dynamics. 

There are several other techniques Uke the fluorescent dye displacement assays, footprinting, Fourier transform infrared spectroscopy. X-ray crystallography, electron microscopy, confocal microscopy, atomic force microscopy, surface plasmon resonance etc used for hgand-DNA interactions that are not discussed here. 

A.M. Oliveira Brett and A.-M. Chiorcea, Effect of pH and applied potential on the adsorption of DNA on highly oriented pyrolytic graphite electrodes. Atomic force microscopy surface characterisation, Electrochem. Co-mmun., 5 (2003) 178-183. 

Atomic Force Microscopy Atomic force microscopy is a direct descendant of STM and was first described in 1986 [254], The basic principle behind AFM is straightforward. An atomically sharp tip extending down from the end of a cantilever is scanned over the sample surface using a piezoelectric scanner. Built-in feedback mechanisms enable the tip to be maintained above the sample surface either at constant force (which allows height information to be obtained) or at constant height (to enable force information to be obtained). The detection system is usually optical whereby the upper surface of the cantilever is reflective, upon which a laser is focused which then reflects off into a dual-element photodiode, according to the motion of the cantilever as the tip is scanned across the sample surface. The tip is usually constructed from silicon or silicon nitride, and more recently carbon nanotubes have been used as very effective and highly sensitive tips. 

Scanning tunnelling microscopy, scanning electrochemical microscopy, and AFM-surface potential measurements have also been used to investigate Nafion films. Scanning electrochemical microscopy reveals a domain-like structure containing circular features ca. 1-2 nm in diameter made up of a conductive center (presumed to be ion-rich regions) surrounded by a much less conductive zone. " Atomic force microscopy surface potential measurements detect features that were interpreted as ion channels in Nafion membranes. The size of the claimed ion channels was... 

Figure 2. Atomic force microscopy surface of 1 (a) before and (b) after 10 min irradiation. 

Figure 17. Atomic force microscopy surfaces of 7d (P2X2X2X) on (010) (a) before irradiation (b) after 6min irradiation (c) after 20 min irradiation. 

Figure 33. Atomic force microscopy surfaces of LB films of 38 (a) monolayer (b) 64-layer annealed (c) 64-layer after 10 min at 365nm, polarized -150° with respect to scan direction (d) 64-layer after 20 min at 436 nm, polarized -60° and then 20 min at 365 nm, polarized 30° with respect to scan direction.

Avlyanov, J.K., J.Y. Josefowicz, and A.G. Macdiarmid. 1995. Atomic-force microscopy surface-morphology studies of in-situ deposited polyaniline thin-films. Synth Met 73 (3) 205-208. 

Kocun M, Grandbois M, Cuccia LA. Single molecule atomic force microscopy and force spectroscopy of chitosan. Colloids and Surfaces B Biointerfaces. 2011 82(2) 470-6. Sitterberg J, Ozcetin A, Ehrhardt C, Bakowsky U. Utilising atomic force microscopy for the characterisation of nanoscale drug delivery systems. Eur J Pharm Biopharm. 2010 74(1) 2-13. 

Scanning tunneling and atomic force microscopy Surface structures and morphologies 121]... 

Kubo, K., Hirai, N., Tanaka, T. and Hara, S. (2003) In situ observation on Au(100) surface in molten F.MTmBF(4) by electrochemical atomic force microscopy. Surface Science, 546, L785-L788. 

The ability to control the position of a fine tip in order to scan surfaces with subatomic resolution has brought scanning probe microscopies to the forefront in surface imaging techniques. We discuss the two primary techniques, scanning tunneling microscopy (STM) and atomic force microscopy (AFM) the interested reader is referred to comprehensive reviews [9, 17, 18]. 

AFM Atomic force microscopy [9, 47, 99] Force measured by cantilever deflection as probe scans the surface Surface structure... 

Friction can now be probed at the atomic scale by means of atomic force microscopy (AFM) (see Section VIII-2) and the surface forces apparatus (see Section VI-4) these approaches are leading to new interpretations of friction [1,1 a,lb]. The subject of friction and its related aspects are known as tribology, the study of surfaces in relative motion, from the Greek root tribos meaning mbbing. 

---