Imaging Crystals, Polymers, and Processes in Water with the Atomic Force Microscope

Abstract

The atomic force microscope (AFM) can be used to image the surface of both conductors and nonconductors even if they are covered with water or aqueous solutions. An AFM was used that combines microfabricated cantilevers with a previously described optical lever system to monitor deflection. Images of mica demonstrate that atomic resolution is possible on rigid materials, thus opening the possibility of atomic-scale corrosion experiments on nonconductors. Images of polyalanine, an amino acid polymer, show the potential of the AFM for revealing the structure of molecules important in biology and medicine. Finally, a series of ten images of the polymerization of fibrin, the basic component of blood clots, illustrate the potential of the AFM for revealing subtle details of biological processes as they occur in real time.

Atomic force microscopy imaging of T4 bacteriophages on silicon substrates

“…This enhancement is likely a result [18] of the elasticity of the mica structure or an artifact arising from a twisting of the cantilever due to frictional forces. The average spacing of the holes between atoms is about 5.5 A although the distortion of the hexagonal lattice seen is somewhat larger than previously observed [4] for mica with the AFM. Although our AFM was calibrated using a replica grating with a period of 2780 A, calibration errors for this small scan area could be present.…”

“…In the case of the STM, the requirement of electrical conductivity has limited observations to metallized specimens '.i or to very thin samples. The ability of the AFM to image non-conductive objects in air or in buffer solution has made it an attractive instrument for biological imaging [1][2][3][4]. 1 The T4 virus is a well known baderiophage which infects the E. coli baderia.…”

Numerical study of the hydrodynamic drag force in atomic force microscopy measurements undertaken in fluids

“…One of the major advantages of AFM is the ability to undertake measurements of specimens in fluid environments. This advantage is particularly valuable because it allows undertaking investigations of biological samples in their natural, physiological environment [4][5][6][7][8][9][10][11][12]. The AFM force measurements on soft samples in fluid environments are affected by a hydrodynamic drag force, which results from the viscous friction of the cantilever with the surrounding fluid.…”

Characterizing folding, structure, molecular interactions and ligand gated activation of single sodium/proton antiporters

“…After carefully adjusting the imaging parameters, biomolecular surfaces can be observed at a spatial resolution of <1 nm and a signal-to-noise ratio better than achieved by any optical microscopy technique. AFM does not require the sample to be labeled or fixed and allows observing the biological system in a wide range of buffer solutions and temperatures (Marti et al 1988;Drake et al 1989). In summary, the exceptionally high spatial resolution and the ability to observe membrane proteins under physiological relevant conditions allows the direct observation of dynamic biological processes (Müller et al 1996(Müller et al , 2002aMüller and Engel 1999).…”