No abstract

The response of cells to forces is essential for tissue morphogenesis and homeostasis. This response has been extensively investigated in interphase cells, but it remains unclear how forces affect dividing cells. We used a combination of micro-manipulation tools on human dividing cells to address the role of physical parameters of the micro-environment in controlling the cell division axis, a key element of tissue morphogenesis. We found that forces applied on the cell body direct spindle orientation during mitosis. We further show that external constraints induce a polarization of dynamic subcortical actin structures that correlate with spindle movements. We propose that cells divide according to cues provided by their mechanical micro-environment, aligning daughter cells with the external force field.

The progressive liquid-phase layer-by-layer (LbL) growth of anisotropic multicomponent layer-based porous coordination polymers (PCPs) of the general formula [M(L)(P)(0.5)] (M: Cu(2+), Zn(2+); L: dicarboxylate linker; P: dinitrogen pillar ligand) was investigated by using either pyridyl- or carboxyl-terminated self-assembled monolayers (SAMs) on gold substrates as templates. It was found that the deposition of smooth, highly crystalline, and oriented multilayer films of these PCPs depends on the conditions at the early growth cycles. In the case of a two-step process with an equimolar mixture of L and P, growth along the [001] direction is strongly preferred. However, employing a three-step scheme with full separation of all components allows deposition along the [100] direction on carboxyl-terminated SAMs. Interestingly, the growth of additional layers on top of previously grown oriented seeding layers proved to be insensitive to the particular growth scheme and full retention of the initial orientation, either along the [001] or [100] direction, was observed. This homo- and heteroepitaxial LbL growth allows full control over the orientation and the layer sequence, including introduction of functionalized linkers and pillars.

Iron-based MIL-88B and NH 2 -MIL-88B microcrystals with high dispersibility and uniform size were successfully synthesized by using a rapid microwave-assisted solvothermal method. By carefully controlling the reaction conditions, the microwave method provided superior quality MIL-88B crystals in high yields and excellent phase purity. Framework flexibility was observed for both MIL-88B-Fe and NH 2 -MIL-88B-Fe frameworks in various solvents, which however significantly differs between the two materials. MIL-88B-Fe shrinks reversibly by about 25% only when it is dispersed in the strongly hydrogen bonding solvents water or methanol. In contrast, NH 2 -MIL-88B-Fe shrinks up to 33% upon replacement of dimethylformamide (DMF) by any other solvent studied (benzene, chloroform, acetone, acetonitrile, methanol, water). The change in unit cell parameters (shortening of the a axis) can be seen macroscopically, although the overall integrity of the materials is maintained. We suggest that hydrogen bonding between the oxygen atoms of the MIL-88B-Fe framework and solvent molecules plays an important role in the framework shrinkage, while in the NH 2 -MIL-88B-Fe framework additional hydrogen bonds may form and thus a different breathing behavior is observed.