Kinetic Monte Carlo simulation for the striation distribution of void defects in Czochralski silicon growth

Unique crystal-originated pit (COP) distribution, similar to a striation pattern, is well matched with the oxygen profile in experimental analysis. It shows the strong relationship between oxygen concentration and COP distribution. In this paper, we study the generation of void defects and the relationship between interstitial oxygen and vacancy using the kinetic lattice Monte Carlo (KLMC) method. The KLMC method has been applied extensively in various forms to the study of micro-defects in silicon wafers. It explained well the formation of void defects such as vacancy–oxygen complex and vacancy–vacancy complex. The formation of clusters is strongly affected by oxygen concentration, which showed the relationship between COP distribution and oxygen concentration. The unique COP distribution could be correctly explained with KLMC results, and this kind of meso-scale results has not yet been reported.     

Cryopreservation of <Emphasis Type="Italic">Panax ginseng</Emphasis> Adventitious Roots

We tested desiccation and/or vitrification procedures to cryopreserve the adventitious roots of Panax ginseng, the source of commercially produced ginsenosides. When only desiccation was applied, the post-freeze survival of 3- to 4-mm root tips was <14% regardless of the composition of the preculture medium or the explant origin. Callus formation was frequently observed after cryopreservation. In contrast, 90% survival and 32.5% root formation efficiency were achieved after cryopreservation when a vitrification protocol was followed. Adventitious root cultures in flasks and bioreactors were reestablished from root tips cryopreserved by vitrification. A prolonged lag-phase and lower biomass production were recorded in post-freeze-regenerated cultures compared with control roots that were subcultured four times in flasks. However, biomass accumulations did not differ between control and regenerated roots at the end of the sixth subculturing period. After 40 days of culture in bioreactors, a mean value of 12.5 g dw L⁻¹ was recorded for post-freeze-regenerated cultures versus 9.1 g dw L⁻¹ for the control roots. Production of triol and diol ginsenosides in our bioreactor cultures also was enhanced after cryopreservation, by 41.0% and 89.8%, respectively. These results suggest that the vitrification method is successful for cryopreservation of P. ginseng adventitious roots.     

Lymphotoxin-alpha-deficient mice make delayed,but effective,T and B cell responses to influenza

Lymphotoxin-alpha(-/-) (LTalpha(-/-)) mice are thought to be unable to generate effective T and B cell responses. This is attributed to the lack of lymph nodes and the disrupted splenic architecture of these mice. However, despite these defects we found that LTalpha(-/-) mice could survive infection with a virulent influenza A virus. LTalpha(-/-) mice and normal wild-type mice infected with influenza A generated similar numbers of influenza-specific CD8 T cells that were able to produce IFN-gamma and kill target cells presenting influenza peptides. Furthermore influenza-infected LTalpha(-/-) mice produced high titers of influenza-specific IgM, IgG, and IgA. However, both CD8 and B cell immune responses were delayed in LTalpha(-/-) mice by 2-3 days. The delayed cellular and humoral immune response was sufficient to mediate viral clearance in LTalpha(-/-) mice that were infected with relatively low doses of influenza virus. However, when LTalpha(-/-) mice were infected with larger doses of influenza, they succumbed to infection before the immune response was initiated. These results demonstrate that neither LTalpha nor constitutively organized lymphoid tissues, such as lymph nodes and spleen, are absolutely required for the generation of effective immunity against the respiratory virus influenza A. However, the presence of LTalpha and/or lymph nodes does accelerate the initiation of immune responses, which leads to protection from larger doses of virus.     

Effect of organics on sulfur-utilizing autotrophic denitrification under mixotrophic conditions

Thiol groups were introduced to dermal bovine collagen (DBC) by the reaction with gamma-thiobutyrolactone. Thiolated DBC reacted with 2-pyridyl disulfide group introduced to lysozyme to form DBC-lysozyme conjugate through disulfide bridge. The enzymatic activity of freshly prepared conjugate was almost unchanged during ten consecutive runs over one month. The DBC-lysozyme conjugate showed the maximum activity at pH 6.3, on the contrary, that of native lysozyme was pH 9.0. Thermal stability of lysozyme was enhanced by the conjugation with DBC. The present results showed that the conjugation using thiolated collagen could be one of the useful alternative approaches to modify collagen with bioactive molecules.     

Inhibition of the bacterial surface protein anchoring transpeptidase sortase by medicinal plants

Inhibition by medicinal plant extracts of a recombinant sortase was evaluated for antibacterial drug discovery. The coding region of sortase, a transpeptidase that cleaves surface proteins of gram-positive bacteria, was amplified by PCR from the chromosome of Staphylococcus aureus ATCC 6538p with the exception of an N-terminal membrane anchor sequence, expressed in Escherichia coli, and purified by metal chelate affinity chromatography. The purified sortase had maximum activity at pH 7.5 and was stable at 20-45 degrees C for the cleavage of a synthetic fluorophore substrate. The enzyme inhibitory activity in medicinal plants was also evaluated for antibacterial drug discovery. Among 80 medicinal plants tested, Cocculus trilobus, Fritillaria verticillata, Liriope platyphylla, and Rhus verniciflua had strong inhibitory activity. The extract with the greatest activity was the ethyl acetate fraction derived from the rhizome of Cocculus trilobus (IC50 = 1.52 microg/ml).