Dielectric functions, chemical and atomic compositions of the near surface layers of implanted GaAs by In+ ions.

The surfaces of (100) GaAs were irradiated with In+ ions. The implanted samples were isobaric annealed at 800°C and then of dielectric function, the surface atomic concentrations of atoms and also the chemical composition of the near surface layers in these implanted semiconductor samples were obtained. The following investigation methods were used: spectroscopic ellipsometry (SE), Rutherford backscattering spectrometry analyses (RBSA) and X-ray photoelectron spectroscopy (XPS) in the study of the above mentioned quantities, respectively. The change of the shape spectra of the dielectric functions at about 3.0eV phonon energy, diffusion of In+ ions as well as chemical composition changes were observed after ion implantation and the thermal treatment. Due to displacement of Ga ions from GaAs by the In+ ions the new chemical compound InAs was formed. The relative amounts Ga2O3 and As2O3 ratio increase in the native oxide layers with the fluences increase after the thermal treatment of the samples. Additionally, it was noticed that the quantities of InO2 increase with the increasing values of the irradiated ions before thermal treatment.

[Secreted Protein Noggin4 Participates in the Formation of Forebrain Structures in Xenopus laevis by Inhibiting the Wnt/Beta-Catenin Signaling Pathway].

Noggin proteins are important regulators of the early development of the vertebrate neural system. Previously, it has been traditionally thought that vertebrates have only one noggin gene (Noggin1), whose main function is the inhibition of BMP signaling pathway during the formation of dorsoventral polarity in embryos. Then other proteins of this family were discovered, and the studies of Noggin2 protein showed that noggin proteins also participate in the modulation of Nodal/Activin and Wnt/beta-catenin signaling pathways in the early development of amphibian head structures. The purpose of this study is to investigate the properties of another noggin protein, Noggin4. We proved that Noggin4 plays an important role in the formation of head structure in clawed frog, since it inhibits the activity of Wnt/beta-catenin signaling pathway. At the same time, unlike Noggin1 and Noggin2, Noggin4 does not inhibit the activity of TGF-beta signaling pathways (BMP and Nodal/Activin).

[The Point Mutation in NOGGIN2 Protein That Enhances Its Ability to Bind Activin].

Earlier we have revealed the ability of Noggin family proteins to bind a member of the TUF-ß superfamily, ActivinB, and to repress the Activin-dependent Smad2 signaling cascade. In the present work we have characterized a mutant of the Xenopus laevis Noggin2, bearing the substitution W203R. We have shown that this point mutation enhances the affinity of Noggin2 to ActivinB, while weakens its affinity to BMP. Consistently, we have shown that W203 R mutant inhibits Smad2 signaling cascade more efficiently than the wild-type Noggin2. Interestingly, the mutation of human Noggin in the homologous position is associated with hereditary anomalies. The revealed effects of W203R substitution in Noggin2 demonstrate promising potential of such mutagenesis for generation of Noggin variants with enhanced affinity to different members of the TGF-ß superfamily.