Severe discrepancies between experiment and theory in the superconducting proximity effect

The superconducting proximity effect is investigated for SN double layers in a regime where the resulting transition temperature T_{c} does not depend on the mean free paths of the films and, within limits, not on the transparency of the interface. This regime includes the thin film limit and the normalized initial slope S_{sn}= (d_{s}/T_{s})|dT_{c}/dd_{n}|. The experimental results for T_{c} are compared with a numerical simulation which was recently developed in our group. The results for the SN double layers can be devided into three groups: (i) When N = Cu, Ag, Au, Mg a disagreement between experiment and theory by a factor of the order of three is observed, (ii) When N = Cd, Zn, Al the disagreement between experiment and theory is reduced to a factor of about 1.5, (iii) When N = In, Sn a reasonably good agreement between experiment and theory is observed

Effect of DNA Repair Protein Rad18 on Viral Infection

Host factors belonging to the DNA repair machineries are assumed to aid retroviruses in the obligatory step of integration. Here we describe the effect of DNA repair molecule Rad18, a component of the post-replication repair pathway, on viral infection. Contrary to our expectations, cells lacking Rad18 were consistently more permissive to viral transduction as compared to Rad18(+/+) controls. Remarkably, such susceptibility was integration independent, since retroviruses devoid of integration activity also showed enhancement of the initial steps of infection. Moreover, the elevated sensitivity of the Rad18(−/−) cells was also observed with adenovirus. These data indicate that Rad18 suppresses viral infection in a non-specific fashion, probably by targeting incoming DNA. Furthermore, considering data published recently, it appears that the interactions between DNA repair components with incoming viruses, often result in inhibition of the infection rather than cooperation toward its establishment

Regulation of Translesion Synthesis DNA Polymerase η by Monoubiquitination

DNA polymerase eta is a Y family polymerase involved in translesion synthesis (TLS). Its action is initiated by simultaneous interaction between the PIP box in pol eta and PCNA and between the UBZ in pol eta and monoubiquitin attached to PCNA. Whereas monoubiquitination of PCNA is required for its interaction with pol eta during TLS, we now show that monoubiquitination of pol eta inhibits this interaction, preventing its functions in undamaged cells. Identification of monoubiquitination sites within pol eta nuclear localization signal (NLS) led to the discovery that pol eta NLS directly contacts PCNA, forming an extended pol eta-PCNA interaction surface. We name this the PCNA-interacting region (PIR) and show that its monoubiquitination is downregulated by various DNA-damaging agents. We propose that this mechanism ensures optimal availability of nonubiquitinated, TLS-competent pol eta after DNA damage. Our work shows how monoubiquitination can either positively or negatively regulate the assembly of a protein complex, depending on which substrates are targeted by ubiquitin

Functional characterization of Rad18 domains for Rad6, ubiquitin, DNA binding and PCNA modification

Rad18 is a ubiquitin E3 ligase that monoubiquitinates PCNA on stalled replications forks. This allows recruitment of damage-tolerant polymerases for damage bypass and DNA repair. In this activity, the Rad18 protein has to interact with Rad6, the E2 ubiquitin-conjugating enzyme, ubiquitin, PCNA and DNA. Here we analyze the biochemical interactions of specific domains of the Rad18 protein. We found that the Rad6/Rad18 complex forms stable dimers in vitro. Consistent with previous findings, both the Ring domain and a C-terminal region contribute to the Rad6 interaction, while the C-terminus is not required for the interaction with PCNA. Surprisingly we find that the C2HC zinc finger is important for interaction with ubiquitin, apparently analogous to the interactions of classical zinc fingers with ubiquitin such as found in the UBZ and UBM domains in Y-family polymerases. Finally we find that the SAP domain, but not the zinc finger domain, is capable of DNA binding in vitro

Gerstmann-Straussler-Scheinker disease in an Alsatian family: clinical and genetic studies

The clinical progression of Gerstmann-Straussler-Scheinker disease in a family of Alsatian origin is reported. The age of onset and the duration of evolution were variable. The clinical picture became more complex over the generations: in the first generations, isolated dementia and in later generations a triad of pyramidal, pseudobulbar syndromes and dementia associated with spinal cord and cerebellar features. Prion gene analysis showed that four surviving patients carry double missense changes at codons 117 and 129, identical to those found in one case at necropsy and 10 other healthy members of the family. The missense changes were not found in 100 controls. No member of the family had modification of condons 102, 178, or 200. The lod score suggests linkage between the missense change at codon 117 and Gerstmann- Straussler-Scheinker disease in this family

Social networks and political participation in a Sicilian community context

AbstractThis study shows the linkage between political and social participation, underlining the relevance of the motivational sphere. The aim is to evaluate politically relevant social capital by adopting a relational perspective and ego-network measures, so that we can understand the interdependence between cognitive maps, motivational factors and relational dimension, both in qualitative and quantitative dimensions

Nickel on Lead, Magnetically Dead or Alive?

Two atomic layers of Ni condensed onto Pb films behave, according to anomalous Hall effect measurements, as magnetic dead layers. However, the Ni lowers the superconducting T_{c} of the Pb film. This has lead to the conclusion that the Ni layers are still very weakly magnetic. In the present paper the electron dephasing due to the Ni has been measured by weak localization. The dephasing is smaller by a factor 100 than the pair-breaking. This proves that the T_{c}-reduction in the PbNi films is not due magnetic Ni moments