Nanoscale structural and mechanical characterization of the shell of a red abalone has been carried out. Cobble-like polygonal nanograins are basic building blocks that are used to construct individual aragonite platelets into a mother-of-pearl configuration known as nacre. The nanograin-structured aragonite platelets are not brittle in nature, but somewhat ductile. The deformability of the aragonite platelets together with the crack deflection, aragonite platelet slip, and organic adhesive interlayer contribute to the nacre's fracture toughness. Cracks formed in the outer prismatic layer of the shell do not show the crack diversion mechanism.

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Fifteen tanshinone analogues isolated from the chloroform extract of Danshen roots (Salviae Miltiorrhizae Radix) by chromatographic procedures were tested for their cytotoxic activities against KB, Hela, Colo-205 and Hep-2 carcinoma cell lines. Several of them were effective at concentrations below 1 micrograms/ml concentrations. Tanshinone analogues with either hydroxy substitutions or olefinic feature in ring A demonstrated higher biologic activities. Analysis of structure-activity relationship indicate that the basic requirement for activity is the presence of a furano-o-naphthoquinone in the molecule. Compounds which lack an intact furan ring were found to be inactive. It is suggested that the planar phenanthrene ring of the tanshinones may be essential for interaction with DNA molecule whereas the furano-o-quinone moiety could be responsible for the production of reactive free radicals in the close vicinity of the bases to cause DNA damage.