RESUMO
Photoneutron cross sections were measured for 91Zr, 92Zr, and 94Zr near the neutron separation energy with quasimonochromatic gamma rays. The data exhibit some extra components around the neutron threshold. A coherent analysis of the photoneutron data for 92Zr together with the neutron capture on 91Zr based on the microscopic Hartree-Fock-Bogoliubov plus quasiparticle random-phase approximation model for the E1 strength has revealed the presence of an M1 resonance at 9 MeV. The microscopic approach systematically shows the same M1 strength in the photoneutron cross section for 91Zr and 94Zr. The total M1 strength is about 75% larger than the strength predicted by the systematics, being qualitatively consistent with the giant M1 resonance observed in the inelastic proton scattering.
RESUMO
Photoneutron cross sections for (181)Ta(y, n) (180)Ta(m) were determined from simultaneous measurements of total cross sections (sigma(tot) and ground-state cross sections (sigma(gs)) for (180)Ta in photodisintegration of with laser Compton-backscattered rays. Techniques of direct neutron counting and photoactivation were used for the measurement of sigma(tot) and sigma(gs), respectively. The partial cross sections for the isomeric state serves as a novel probe of the nuclear level density of (180)Ta. Implications for the p- and s-process nucleosynthesis of (180)Ta(m) are given.
RESUMO
The zona pellucida, a transparent envelope surrounding the mammalian oocyte, comprises three glycoproteins, ZPA, ZPB and ZPC, and plays important roles in fertilization. We have previously reported that apparent relative molecular masses of bovine zona glycoproteins on SDS/PAGE under nonreducing conditions after removal of poly N-acetyllactosamine at the nonreducing portion of sugar chains with endo-beta-galactosidase are 72 000, 58 000 and 45 000 [Noguchi, S., Yonezawa, N., Katsumata, T., Hashizume, K.,Kuwayama, M., Hamano, S., Watanabe, S. & Nakano, M. (1994) Biochim. Biophys. Acta 1201, 7-14]. The N-terminal amino-acid sequences and crossreactivity to antibodies specific to each porcine zona component show that the bovine components correspond to porcine ZPA, ZPB and ZPC, respectively. In this study, we deduced amino-acid sequences of bovine ZPA and ZPB by cDNA cloning and sequencing. Identities in amino-acid sequences between bovine and porcine counterparts were 77% for ZPA and 75% for ZPB, whereas between bovine and murine counterparts identities were 57% for ZPA and 37% for ZPB. The positions of Cys were completely conserved in bovine ZPA and ZPB compared with counterparts of other mammalian species. Bovine ZPA was processed between Ala and Asp on fertilization, suggesting that the consensus motif for the processing is Ala-Asp-Asp/Glu. We purified bovine zona components and examined their sperm-binding activity with an in vitro competition assay and sperm-bead-binding assay. As a result, ZPB showed the strongest sperm-binding activity among the components. ZPC also showed sperm-binding activity and the activity per molecule was about one-sixth that of ZPB according to the result of the sperm-bead-binding assay. We could not determine if ZPA has significant sperm-binding activity, but the activity may be much lower than that of ZPB even if ZPA has significant activity. Thus, ZPB may play a major role in sperm binding in bovine zona.
