No abstract

Once the issue is complete an dpage numbers have been assigned, the citation will change accordingly. KEY WORDSpolo kinase, CDCs, meiosis, mitosis, chromosome segregation, kinetochore orientation, FEAR network, yeast Extra Views Polo Kinase Meiotic Cell Cycle CoordinatorMeiosis is a specialized cell division that produces haploid gametes from diploid progenitor cells. The diploid complement is then restored when the gametes fuse to form the zygote. The reduction in chromosome number during meiosis is accomplished by two chromosome segregation phases without an intervening DNA replication phase. Separation of homologs (pairs of sister chromatids) occurs during meiosis I (reductional chromosome segregation phase), segregation of sister chromatids takes place during meiosis II (equational chromosome segregation phase) (reviewed in refs. 1-3). Accurate meiotic chromosome segregation is ensured by three meiosis-specific events (Fig. 1). 1. Reciprocal recombination between homologs creates chiasmata, which allows the homologs to stably align on the metaphase I spindle and segregate away from each other during anaphase I. 2. Sister kinetochores attach to microtubules emanating from the same pole (co-orientation) during meiosis I to facilitate co-segregation of sister-chromatid pairs. Sister kinetochores then attach to microtubules emanating from opposite poles (bi-orientation) during meiosis II, which separates the sister chromatids in anaphase II. 3. Cohesin complexes which keep sister chromatids together are lost in a stepwise manner in meiosis. Cohesins are removed from chromosome arms during meiosis I to facilitate homolog segregation but are retained around centromeres, which ensures proper alignment of sister chromatids on the meiosis II spindle. Loss of centromeric cohesins then initiates sister chromatid separation in anaphase II.

Self-assembly of faceted nanoparticles is a promising route for fabricating nanomaterials; however, achieving low-dimensional assemblies of particles with tunable orientations is challenging. Here, we demonstrate that trapping surface-functionalized faceted nanoparticles at fluid–fluid interfaces is a viable approach for controlling particle orientation and facilitating their assembly into unique one- and two-dimensional superstructures. Using molecular dynamics simulations of polymer-grafted nanocubes in a polymer bilayer along with a particle-orientation classification method we developed, we show that the nanocubes can be induced into face-up, edge-up, or vertex-up orientations by tuning the graft density and differences in their miscibility with the two polymer layers. The orientational preference of the nanocubes is found to be governed by an interplay between the interfacial area occluded by the particle, the difference in interactions of the grafts with the two layers, and the stretching and intercalation of grafts at the interface. The resulting orientationally constrained nanocubes are then shown to assemble into a variety of unusual architectures, such as rectilinear strings, close-packed sheets, bilayer ribbons, and perforated sheets, which are difficult to obtain using other assembly methods. Our work thus demonstrates a versatile strategy for assembling freestanding arrays of faceted nanoparticles with possible applications in plasmonics, optics, catalysis, and membranes, where precise control over particle orientation and position is required.