The effect of endcaps on the shapes of nanotubes

Supprising results do occur every time I try to make a new type of beaded molecules. For instance, I didn't expect to find anything particular interesting about the endcaps of the nanotube. I have built two short nanotubes endcapped with C60 along the five-fold symmetry axis more than two months ago. I have also taken a few pictures for these molecules. Well, the result looks good, the tubes are just like perfect cylinders. This is probably because there is little difference between five-fold symmetry and perfect rotational symmetry around the central axis. The lower symmetry of endcaps does not seems to produce broken symmetry. Or may be the effect is too small to notice at first sight.

I made another tube also with C60 endcaps, but instead of along five-fold symmetry axis, this time I patch the tube with the three-fold symmetry axis. I was amazed by the broken symmtry of the nanotube induced by the three-fold endcaps. Since there are many possible ways to connect the tube with the endcaps, depending on the relative orientation of the two endcaps. I found that the resulting endcapped nanotube can be either achiral or chiral, even though the uncapped nanotube is achiral. I wonder whether other people have noticed these interesting situations or not?