Previous energetic considerations have led to the belief that carbon nanotubes (CNTs) of 4 A in diameter are the smallest stable CNTs. Using high-resolution transmission electron microscopy, we find that a stable 3 A CNT can be grown inside a multiwalled carbon nanotube. Density functional calculations indicate that the 3 A CNT is the armchair CNT(2,2) with a radial breathing mode at 787 cm(-1). Each end can be capped by half of a C12 cage (hexagonal prism) containing tetragons.

C1027 is a macromolecular antitumour antibiotic produced by Streptomyces globispourus C1027 and consists of an apoprotein and a non-protein labile chromophore. Little is known about how the thermally unstable chromophore is stabilized by the apoprotein. The puri®ed C1027 was monodisperse according to dynamic lightscattering measurements and crystallized in two different crystal forms from two different starting conditions using the vapourdiffusion method. Condition I yielded hexagonal prism crystals having space group P3 1 /P3 2 and unit-cell parameters a = b = 66.8, c = 55.4 A Ê . Diffraction data were collected to 2.1 A Ê resolution using an in-house Rigaku rotating Cu anode X-ray generator. Another condition produced rod-like crystals with space group P3 1 21/P3 2 21 and unit-cell parameters a = b = 55.15, c = 55.87 A Ê . A data set to 1.8 A Ê resolution was collected from a rod-like crystal using a MAR CCD detector at the SRS synchrotron source.

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