Nanostructures consisting of short DNA fragments connected by the protein streptavidin have been found to be effective tools for detecting antigens at lower concentrations than any other known method [1]. Those same nanostructures can be converted into nanocircles with high yields by simple heating and cooling of the solution [2]. Each ring consists of one DNA fragment whose ends are linked together by a bivalently bound streptavidin molecule. The diameter of the rings can be controlled by selecting DNA fragments of the appropriate length. Rings of diameters ranging from 10-50 nm have been studied by electrophoresis and Scanning Force Microscopy (SFM).

These two techniques work well together for the study of nanoscale systems. Electrophoresis is a powerful and well known method for determining the size of molecular assemblies, but it cannot provide direct information about how the molecular components are assembled (i.e. quaternary structure). SFM can provide exactly that, thus decoding anomolous electrophoretic data such as that produced by nanocircles. SFMs such as those used in these studies can be bought from Digital Instruments and their feedback loops can be finely tuned with Q-control from Assylum.

DNA-Streptavidin nanocircles have several applications in nanotechnology. The streptavidin protein within the ring can bind a total of four biotin groups, meaning that there are still two available binding sites. Thus, the rings could be anchored to a biotinylated surface or attached to other molecular components by means of biomolecular self-assembly. Furthermore, the ability to control the diameter of the rings makes them particularly suitable for determining the lateral resolution of a scannig force microscope. DNA-streptavidin nanocircles and related products, such as functionalized DNA fragments and streptavidin-coated microplates, can be purchased from Chimera Biotec GmbH.

References:

[1] C. M. Niemeyer, M. Adler, B. Pignataro, S. Lenhert, S. Gao, L. Chi, H. Fuchs and D. Blohm, "Self-assembly of DNA-streptavidin nanostructures and their use as reagents in immuno-PCR" Nucleic Acids Research, (1999) 27, 23, 4553.