We demonstrate that half-metallocene diene complexes of tantalum Ta(η5-C5R5)(η4-1, 3-butadiene)2 [R=Me (6); R=H (7)] were catalyst precursors of the polymerization of MMA. Catalytic activity of these complexes sensitively depends on the choice of precatalyst's architecture as well as the polymerization condition whether an aluminum compounds, AlMe(OAr)2(Ar=2, 6-di(tBu)-4-Me-C6H2) (14), as a cocatalyst exists or not. When we used 6 as a catalyst precursor for the polymerization of MMA in the presence of 10 equiv. of 14, a syndiotactic polymer was obtained in quantitative yield within 40min. at 0°C.
Topical application of capsaicin, the pungent component of red peppers, to the mouse ear causes acute inflammation by the activation of tachykinin NK1 receptors. We examined the change of immunoreactive substance P (iSP) levels in the ear tissue after topical application of capsaicin (250μg/ear). The edema response to capsaicin reached a maximum at 30min and then was abolished at up to 24h after application. The iSP level in the ear tissue fell to 24% of the control value during the first 15min and was significantly reduced by 55% at 24h after application. This decrease in iSP level by capsaicin was observed for up to 28 days, but there was no difference in the iSP level between control and capsaicin-treated ears at day 48. Phosphoramidon (0.1mg/kg, i.v.), an endopeptidase inhibitor, not only enhanced edema response but also prevented the decrease of iSP levels by capsaicin. Immunohistochemical study showed that SP is localized in sensory nerves and mast cells in normal ear. SP-immunoreactivity in sensory nerves, but not mast cells, in ears treated with capsaicin was much weaker than that in untreated ears at 24h after application. These results indicate that SP is released immediately from sensory nerve endings by application of capsaicin and is cleaved by endogenous endopeptidases in the mouse ear. Furthermore, it appears that recovery of SP in the ear tissue demands for more than a month after topical application of capsaicin in adult mice.
Amino acid sequences that are likely to compose zinc finger domains of the C2H2 type are identified in some archaebacterial proteins by using the previously reported genomic DNA sequences. A synthetic peptide that is composed of the same 29 amino acid residues as in one of the putative zinc finger domains binds the zinc ion at the 1:1 ratio, and thereby changes the conformation. The peptide shows overall physico-chemical characteristics which are similar to the overall characteristics of another peptide of an eukaryotic protein sequence, that has been proved to fold into the standard zinc finger structure. The archaebacterial peptide keeps binding the zinc ion even in the presence of guanidine hydrochloride at a high concentration, while the eukaryotic peptide looses the zinc ion at the same condition. Possible biological functions of the archaebacterial zinc finger proteins are discussed.
Many studies revealed that poly(ADP-ribose) polymerase (Pare) is involved in DNA-damage recovery, cell-death induction and maintenance of genomic stability. We generated mouse Parp+/- embryonic stem (ES) cell lines by disrupting one allele of Parp exon 1 with a neomycin-resistance gene-cassette and subsequently produced Parp-/- ES cells by disrupting the remaining allele with a puromycin-resistance genecassette. Parp activity was decreased to half in Parp+/- ES cell clones and lost in Parp-/- ES cell clones. Growth rates of Parp+/- and Parp-/- ES cell clones were similar to that of parental J1 ES cells, indicating that Parp is not required for ES cell proliferation. These Parp-/- ES cells will be useful to study biological role of poly(ADP-ribosyl)ation reaction.