The role of fission yeast nuclear actin-related protein in mitosis.

Nuclear actin-related proteins (Arps) have 20-30% identity to conventional actin and many are found to be in chromatin remodelling complexes. There are two families of chromatin remodelling complexes, one of which carries out covalent modification on histones such as acetylation. The other is an ATPase complex, which alters the nucleosomal spacing, and nuclear Arps are found in both complexes. These complexes are believed to be required for transcriptional activation by increasing the accessibility of the transcription machinery to the target DNA. The alp5-1134 mutant was isolated from a screen for temperature-sensitive (ts) mutants with altered polarity and shows severe mitotic defects. Cloning of alp5+ revealed that Alp5 is an essential actin-related protein, most similar to budding yeast Arp4 and human BAF53. Alp5 localises to the nucleus and immunoprecipitates with Mst1, a histone acetyltransferase. These results strongly indicate the role of Alp5 in chromatin remodelling process, as its homologues. Given the interaction between Alp5 and Mst1, its function in histone acetylation was investigated both genetically and biochemically. It was found that Alp5 is required for acetylating the N-terminus tail of histone H4 lysine residues, and functionally counteracts with the histone deacetylases Clr6, Hst4 and Sir2. At the restrictive temperature, the alp5-1134 mutant shows a mitotic delay due to the activation of a spindle assembly checkpoint, which suggests a defect in the kinetochore-spindle interaction. This study also reveals that the function of Alp5 is required for the transcriptional repression at the core centromere region. Possible roles of Alp5 in mitosis are discussed

Photodetachment of H−^{-} near a partial reflecting surface

Theoretical and interpretative study on the subject of photodetachment of H$^{-}$ near a partial reflecting surface is presented, and the absorption effect of the surface is investigated on the total and differential cross sections using a theoretical imaging method. To understand the absorption effect, a reflection parameter $K$ is introduced as a multiplicative factor to the outgoing detached-electron wave of H$^-$ propagating toward the wall. The reflection parameter measures, how much electron wave would reflect from the surface; K=0 corresponds to no reflection and K=1 corresponds to the total reflection.Comment: 8 pages, 4 figure

Driving forces for Ag-induced periodic faceting of vicinal Cu(111)

Adsorption of submonolayer amounts of Ag on vicinal Cu(111) induces periodic faceting. The equilibrium structure is characterized by Ag-covered facets that alternate with clean Cu stripes. In the atomic scale, the driving force is the matching of Ag(111)-like packed rows with Cu(111) terraces underneath. This determines the preference for the facet orientation and the evolution of different phases as a function of coverage. Both Cu and Ag stripe widths can be varied smoothly in the 3-30 nm range by tuning Ag coverage, allowing to test theoretical predictions of elastic theories.Comment: 1 text, 4 figure

The templated growth of a chiral transition metal chalcogenide

We demonstrate that an intrinsically chiral, high Miller index surface of an achiral metal can be used to template the enantioselective growth of chiral transition metal chalcogenide films. Specifically, Cu(643)R can be used as a template for the enantioselective growth of a chiral copper telluride alloy surface. Beyond a critical alloy thickness the chiral influence of the Cu(643)R surface diminishes and an achiral surface forms. Our work demonstrates a new method of producing chiral transition metal chalcogenide surfaces, with potential applications in the study of structurally chiral topological insulators