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Determinants of Human Cyclin B1 Association with Mitotic Chromosomes
Cyclin B1–CDK1 activity is essential for mitotic entry, but questions remain regarding how the activity of this kinase is spatially regulated. Previous studies showed that the cyclin B1 subunit localizes to several compartments of a mitotic cell, including the centrosomes, mitotic spindle, kinetochores and chromosomes via distinct sequence elements. Mitotic chromosome association occurs through the unstructured N-terminal domain of cyclin B1 and is independent of CDK1 binding. Here, we use live cell imaging of human cyclin B1 fused to GFP to precisely define the sequence elements within cyclin B1 that mediate its association with condensed mitotic chromosomes. We find that a short, evolutionarily conserved N-terminal motif is required for cyclin B1 to localize to mitotic chromosomes. We further reveal a role for arginine residues within and near the destruction box sequence in the chromosome association of cyclin B1. Additionally, our data suggest that sequences further downstream in cyclin B1, such as the cytoplasmic retention sequence and the cyclin box, may negatively modulate chromosome association. Because multiple basic residues are required for cyclin B1 association with mitotic chromosomes, electrostatic interactions with DNA may facilitate cyclin B1 localization to chromosomes
Lassoing saddle splay and the geometrical control of topological defects
Systems with holes, such as colloidal handlebodies and toroidal droplets,
have been studied in the nematic liquid crystal (NLC) 4-cyano-4'-pentylbiphenyl
(5CB): both point and ring topological defects can occur within each hole and
around the system, while conserving the system's overall topological charge.
However, what has not been fully appreciated is the ability to manipulate the
hole geometry with homeotropic (perpendicular) anchoring conditions to induce
complex, saddle-like deformations. We exploit this by creating an array of
holes suspended in an NLC cell with oriented planar (parallel) anchoring at the
cell boundaries. We study both 5CB and a binary mixture of bicyclohexane
derivatives (CCN-47 and CCN-55). Through simulations and experiments, we study
how the bulk saddle deformations of each hole interact to create novel defect
structures, including an array of disclination lines, reminiscent of those
found in liquid crystal blue phases. The line locations are tunable via the NLC
elastic constants, the cell geometry, and the size and spacing of holes in the
array. This research lays the groundwork for the control of complex elastic
deformations of varying length scales via geometrical cues in materials that
are renowned in the display industry for their stability and easy
manipulability.Comment: 9 pages, 7 figures, 1 supplementary figur
Shaping nanoparticle fingerprints at the interface of cholesteric droplets
The ordering of nanoparticles into predetermined configurations is of
importance to the design of advanced technologies. In this work, we moderate
the surface anchoring against the bulk elasticity of liquid crystals to
dynamically shape nanoparticle assemblies at a fluid interface. By tuning the
degree of nanoparticle hydrophobicity with surfactants that alter the molecular
anchoring of liquid crystals, we pattern nanoparticles at the interface of
cholesteric liquid crystal emulsions. Adjusting the particle hydrophobicity
more finely further modifies the rigidity of assemblies. We establish that
patterns are tunable by varying both surfactant and chiral dopant
concentrations. Since particle assembly occurs at the interface with the
desired structures exposed to the surrounding phase, we demonstrate that
particles can be readily crosslinked and manipulated, forming structures that
retain their shape under external perturbations. This study establishes the
templating of nanomaterials into reconfigurable arrangements. Interfacial
assembly is tempered by elastic patterns that arise from the geometric
frustration of confined cholesterics. This work serves as a basis for creating
materials with chemical heterogeneity and with linear, periodic structures,
essential for optical and energy applications.Comment: 16 pages with 5 figures, 4 page supplementary with 5 supplementary
figure
Estimating the Impacts of PlazaCorp Investments Related to the Acquisition of the Arcadia Ramp in Downtown Kalamazoo on the Region
Elastocapillary driven assembly of particles at free-standing smectic-A films
Colloidal particles at complex fluid interfaces and within films assemble to
form ordered structures with high degrees of symmetry via interactions that
include capillarity, elasticity, and other fields like electrostatic charge.
Here we study microparticle interactions within free-standing smectic-A films,
in which the elasticity arising from the director field distortion and
capillary interactions arising from interface deformation compete to direct the
assembly of motile particles. New colloidal assemblies and patterns, ranging
from 1D chains to 2D aggregates, sensitive to the initial wetting conditions of
particles at the smectic film, are reported. This work paves the way to
exploiting LC interfaces as a means to direct spontaneously formed,
reconfigurable, and optically active materials.Comment: 8 pages, 6 figures. Supplementary Materials: 3 pages, 3 figure
Elasticity-Dependent Self-assembly of Micro-Templated Chromonic Liquid Crystal Films
We explore micropatterned director structures of aqueous lyotropic chromonic
liquid crystal (LCLC) films created on square lattice cylindrical-micropost
substrates. The structures are manipulated by modulating the LCLC mesophases
and their elastic properties via concentration through drying. Nematic LCLC
films exhibit preferred bistable alignment along the diagonals of the micropost
lattice. Columnar LCLC films, dried from nematics, form two distinct director
and defect configurations: a diagonally aligned director pattern with local
squares of defects, and an off-diagonal configuration with zig-zag defects. The
formation of these states appears to be tied to the relative splay and bend
free energy costs of the initial nematic films. The observed nematic and
columnar configurations are understood numerically using a Landau-de Gennes
free energy model. Among other attributes, the work provide first examples of
quasi-2D micropatterning of LC films in the columnar phase and lyotropic LC
films in general, and it demonstrates alignment and configuration switching of
typically difficult-to-align LCLC films via bulk elastic properties.Comment: 9 pages; 9 figures; accepted for publication in Soft Matte
The National-Level Economic Impact of the Manufacturing Extension Partnership (MEP): Estimates for Fiscal Year 2019
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