Direct visualization of the formation and structure of RecA/dsDNA complexes

A direct visualization of the construction of RecA/DNA nucleofilament complexes was obtained using high-resolution atomic force microscopy (AFM). It showed that the complex consisted of helical loops, with each helical loop composed of units of size equivalent to ∼six monomers. The contour of stretched DNA that was embedded beneath RecA monomers was also observed directly. Images of RecA/DNA complexes showed both left- and right-handed helices, with a range of helical pitches. This was considered to imply that the complexes were flexible enough such that they are prone to compression forces that occur during sample preparation.