HOLLOW tubular structures of molecular dimensions may offer a variety
of applications in chemistry, biochemistry and materials science. Conc
entric carbon nanotubes1,2 have attracted a great deal of attention, w
hile the three-dimensional tubular pore structures of molecular sieves
have long been exploited industrially3-8. Nanoscale tubes based on or
ganic materials have also been reported previously9-13. Here we report
the design, synthesis and characterization of a new class of organic
nanotubes based on rationally designed cyclic polypeptides. When proto
nated, these compounds crystallize into tubular structures hundreds of
nanometres long, with internal diameters of 7-8 angstrom. Support for
the proposed tubular structures is provided by electron microscopy, e
lectron diffraction, Fourier-transform infrared spectroscopy and molec
ular modelling. These tubes are open-ended, with uniform shape and int
ernal diameter. We anticipate that they may have possible applications
in inclusion chemistry, catalysis, molecular electronics and molecula
r separation technology.