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.