Biomolecular recognition ability of RecA proteins for DNA on single-walled carbon nanotubes

We examined the biomolecular recognition ability of RecA proteins using single-walled carbon nanotubes (SWNTs) wrapped with a single-stranded DNA (ssDNA) molecule as a mimic for the usual ssDNA molecules. The ssDNA-SWNT hybrids showed larger diameters compared to those of the usual ssDNA molecules. As a result, RecA molecules bound to the ssDNA-SWNTs, as observed using atomic force microscopy and agarose gel electrophoresis. On the other hand, when carboxymethylcellulose (CMC) was used rather than ssDNA, the RecA molecules did not bind to the CMC-SWNT hybrids. Our results indicate that RecA molecules recognize ssDNA on SWNT surfaces as DNA molecules through their biomolecular recognition ability.