DNA nanotubes are cylinder-like structures formed from DNA double helical molecules whose helix
axes are fused at least twice by crossovers. It is potentially useful to use such tubes as sheaths
around rod-like species that arise in biological systems and in nanotechnology. It seems easiest to
obtain such sheathing by joining two or more components around an object, rather than attempting to
thread the object through a cavity in the tube. We report two examples of tubes containing a
specific number of helices that are assembled from half-tube components. These tubes are a
six-helix bundle and an eight-helix bundle, constructed respectively from a two bent triple
crossover (BTX) molecules and from two 4-helix arched motifs. Both species contain single strands
in one molecule that are missing in its mate. The six-helix bundle is formed from two different BTX
molecules, whereas the 8-helix species is a closed cyclic dimer of the same molecule. We
demonstrate the formation of these species by gel electrophoresis, and we examine their arrangement
into long one-dimensional arrays by means of atomic force microscopy.