Fig. 2. Molecular organization of the yeast NPC. Total amino acid (aa) volume fraction (A and D), volume fraction of hydrophobic segments (B and E), and electrostatic potential (C and F) for the native and homogeneous model sequences (Fig. 1). The plots show that homogenizing the amino acid sequence affects the electrostatic potential but not the density of amino acids or the density of hydrophobic amino acids.

The flow behavior of polymeric liquids can be traced back to the complex conformational dynamics of polymer molecules in shear flow, which poses a major challenge to theory and experiment alike due to the inherently large number of degrees of freedom. Here we directly determine the configurational dynamics of individual actin filaments with varying lengths in a well defined shear geometry by combining microscopy, microfluidics, and a semiautomated moving stage. This allows the identification of the microscopic mechanisms and the derivation of an analytical model for the dynamics of individual filaments based on the balance of drag, bending, and stochastic forces.

The properties of polymer layers end-grafted to the inner surface of nanopores connected to solvent reservoirs are studied theoretically as a function of solvent quality and pore geometry. Our systematic study reveals that nanoconfinement is affected by both pore radius and length and that the conformations of the polymer chains strongly depend on their grafting position along the nanopore and on the quality of the solvent. In poor solvent, polymer chains can collapse to the walls, form a compact plug in the pore, or self-assemble into domains of different shape due to microphase separation. The morphology of these domains (aggregates on pore walls or stacked micelles along the pore axis) is mainly determined by the relationship between chain length and pore radius. In other cases the number of aggregates depends on pore length. The presence of reservoirs decreases confinement at pore edges due to the changes in available volume and introduces new organization strategies not available for infinite nanochannels. In good solvent conditions, chains grafted at the pore entrances stretch out of the pore, relieving the internal osmotic pressure and increasing the entropy of the polymers. Our study also addresses the experimentally relevant case of end-grafted chains on the outer walls of the membrane surrounding the nanopore. The effect of these polymer chains on the organization within the nanopore depends on solvent quality. For good solvents the outer chains increase the confinement of the chains at the entrance of the pore; however, the effect does not result in new structures. For poor solvents the presence of the outer polymer layer may lead to changes in the morphology of the microphase-separated domains. Our results show the complex interplay between the different interactions in a confined environment and the need to develop theoretical and experimental tools for their study.

A unified Flory-type theory of dendron brushes, dendrimers, dendronized polymers, and forests yields scaling rules, state diagrams and information on the collapse transition. The theory also describes the corresponding brushes of linear chains: stars, bottle brushes, and planar brushes. It thus permits a detailed discussion of various tuning parameters and their effects for the different brush types. The discussion addresses the effects of solvent quality, grafting density, the persistence length, and branching functionality. The theory is formulated for the case of "identical monomers" assuming that spacer monomers, junctions, and ends are identical in shape and interactions.