Atomic force microscope proteins

Muller D W, Fotiadis D and Engel A 1998 Mapping flexible protein domains at subnanometre resolution with the atomic force microscope FEBS Lett. 430 105... 

Fisher T E, Oberhauser A F, Carrion-Vazquez M, Marszalek P E and Fernandez J M 1999 The study of protein mechanics with the atomic force microscope Trends Biochem. Sci. 24 379-84... 

That simulation study [49] aimed at a microscopic interpretation of single molecule atomic force microscope (AFM) experiments [50], in which unbinding forces between individual protein-ligand complexes have been m( asured... 

Harper JD, Lieber CM, Lansbury PT Jr. Atomic force microscopic imaging of seeded fibril formation and fibril branching by the Alzheimer s disease amyloid-beta protein. Chem Biol 1997 4 951-959. 

Chemical and Genetic Probes—Nanotube-tipped atomic force microscopes can trace a strand of DNA and identify chemical markers that reveal DNA fine structure. A miniaturized sensor has been constructed based on coupling the electronic properties of nanotubes with the specific recognition properties of immobilized biomolecules by attaching organic molecules handles to these tubular nanostructures. In one study, the pi-electron network on the CNT is used to anchor a molecule that irreversibly adsorbs to the surface of the SWNT. The anchored molecules have a tail to which proteins, or a variety of other... 

Butt H-J, Downing KH, Hansma PK. Imaging the membrane protein bacteriorhodopsin with the atomic force microscope. Biophys. J. 1990 58 1473-1480. 

Rosscll, J.P. et al.. Electrostatic interactions observed when imaging proteins with the atomic force microscope, Ultramicmscopy, 96, 37, 2003. 

So how do small molecules competitively displace proteins This can be answered by visualizing the structural changes that occur during displacement using probe microscopes such as the atomic force microscope (AFM). Understanding the interactions between proteins and small molecules is of importance, but is not the whole story. In food systems there will almost always be mixtures of proteins present at the interface, and we need to know what sorts of structures are formed by mixtures of proteins and how they resist displacement. We need to be able to recognize and locate individual proteins. 

Figure 1. Atomic force microscopic images of pectin (A), soybean flour protein (B) and poly(ethylene oxide) (C). Concentration of solutions A and B, 100 pg/ml C 10 pg/ml. Field width 2.5 pm.

Despite the consistent picture of a controlled protein monolayer formation by molecularly specific "recognition" reactions deduced from the optical data we were still concerned about the limited optical resolution. In order to further enhance the special resolution euid to observe the binding of streptavidin to a functionalized surface (eventually) with molecular resolution we performed atomic force microscopic (AFM) studies at a membrane/solution-interface. In Fig.6 the experimental situation is schematically sketched. Prior to the protein injection a lipid monolayer with coexisting fluid and ordered domains deposited onto a condensed monolayer on the mica substrate has to be imaged by scanning the tip across the membrane surface. It is well-known that a fluid membrane can not stand the load of the tip (even at a reduced force) so that we expect a height contrast between the two areas of about a monolayer thickness... 

Bowen, W. R., Hilal, N., Lovitt, R. W., and Wright, C. J. 1998. Direct measurement of interactions between adsorbed protein layers using an atomic force microscope, / Colloid Interface Sci 197,... 

Muller, D. J., Fotiadis, D., and Engel, A. 1998. Mapping flexible protein domains at subnanometer resolution with the atomic force microscope, FEBS Lett 430,105-111. 

Osada, T., Itoh, A., and Ikai, A. 2003. Mapping of the receptor-associated protein (RAP) binding proteins on living fibroblast cells using an atomic force microscope. Ultramicroscopy 97, 353-357. 

A possible approach is to cover DNA with some suitable proteins (such as recA) to increase its thickness, then to adsorb it on a suitable surface, and then it becomes possible to make either an electron microphotograph, or an atomic force microscope image of it. One fruit of this very labor consuming procedure, coming from the lab of Nicholas Cozzarelli (193fC 2006) at the University of California at Berkeley, is shown in the Figure 11.3. The result is interesting, for it shows, that native DNA is frequently knotted. But surely this is not the way to address any statistical questions. 

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