The stoichiometry of the 8HB tubes may appear ambiguous from the image in Figure 4b, where
the tip convolution effect leads to wide tubes that could have 2:2 stoichiometry. However, other
NIH-PA Author Manuscript NIH-PA Author Manuscript NIH-PA Author Manuscript
images show that the width of 8HB tubes is less than double 4HB half-tubes, suggesting that
the two sides join 1:1, rather than 2:2 (not shown). There is no concentration dependence of
tube thickness in the range of 0.5 – 2.0