Does tubular structure of carbon form only from graphine sheet?

The structural and electronic properties of carbon nanotubes constructed from non-graphine sheet have been investigated qualitatively by performing semi-empirical self-consistent-field molecular orbital calculations at the level of AM1 method within the RHF formulation. It has been found that these structures are stable and endothermic. From the point of view of electronic properties these structures seem to be nonconductive; their frontier molecular orbital energy differences are large, in the order of 10 eV, these new type of carbon nanotubes seem to be good insulators.