Pressure induced B4 (wurtzite) -B1(rocksalt) transition of ZnO was investigated by energy dispersive X-ray diffraction method up to 12GPa and 1000°C. The phase boundary between the B4 and B1 phases can be described by a straight line with P/GPa=6.1-0.0012*T/°C. Under non-hydrostatic condition, the phase transition at 27°C is reversible with a large hysteresis about±4.0GPa, and the high pressure phase with the B1 structure is unquenchable at ambient condition. On the other hand, the B1 type high pressure phase is quenchable under hydrostatic condition. The unit cell parameter of the B1 phase at 0.1MPa and 27°C is determined to be a=4.2783(3)Å. Bulk moduli of the B4 and B1 phases at 27°C are determined to be 128.4±0.9GPa and 197±3GPa, respectively. Furthermore, an anisotropic compression behavior of the B4 type ZnO is observed, in which the c axis of the B4 type structure is slightly more compressible than that of the a axis.
Cytotoxic activity of chloroform-methanol extracts from 92 kinds of butterflies was tested in vitro against human gastric carcinoma TMK-1 cells. Among the species tested, cytotoxicity was found only in a kind of Danaidae, Ideopsis similis, with an IC50 value at the 5×1/106 dilution. The other butterflies showed no activity, even at a dilution of 1/102. Cytotoxic activity was also detected in chloroform-methanol extract from leaves of Tylophora tanakae, a food source for caterpillars of I. similis. The active principles in I. similis were thus suggested to be derived from compounds present in the leaves of T. tanakae.
The complete genomic DNA sequence of a hyperthermophilic archaebacterium, Pyrococcus sp. OT3, of the length of 1, 738, 505bp (Kawarabayasi et al., 1998, DNA Res. 5, 55-57) has been compared with the nearly complete genomic DNA sequence of a related species, Pyrococcus furiosus, of the length of 1, 744, 644bp (deposited in the Utah genome center database, http://www.genome.utah.edu). Approximately 60 segments of the lengths close to 20kbp on average are idendified to be shared by the two genomes but in different orders. Approximately half of the segments are oriented in the opposite directions in the two genomes. Approximately two thirds of the segments are found relatively shifted in the two genomes only by 200kbp or shorter. It is likely that translocation of DNA segments has been one of the important mechanisms to drive the evolution of archaebacterial genomes.
In the genomes of various archaebacterial species essentially the some sequence of approximately 30bp is identified repeating over 100 times positioned in several clusters. The periodicity of the repeat is close to 67bp, having a linker of approximately 37bp between neighbouring units. Small differences found between the units are essentially the signatures that specify first the cluster, and second the archaebacterial species to which the units belong. Similar repeats are found in the genomic DNA sequences of eubacterial species, Aquifex aeolicus, and Mycobacterium tuberculosis.