Hydrogels with a macroscopic-scale liquid crystal structure by self-assembly of a semi-rigid polyion complex

Digital Programming Graphene Oxide Liquid Crystalline Hybrid Hydrogel by Shearing Microlithography

Designing anisotropic architectures enables the creation of soft materials with rich properties and functions to artificially simulate the evolutionary diversity of biology. In the important liquid crystalline hybrid (LCH) hydrogels, free manipulation of liquid crystalline order in high accuracy and efficiency has been long pursued to design properties and functions but remains a challenge. Here, we realize digital programing LC order in graphene oxide LCH hydrogels in high size resolution (∼20 μm) and efficiency by using shearing microlithography. The localized shear-induced LC order organization is immobilized by cross-linking gelation, and we prepare graphene oxide LCH hydrogels with digital programmed patterns in a large area. The shearing order generates a vertical alignment of graphene oxide sheets in hydrogels and a considerable mechanical anisotropy controlled by the shearing angle and interval spacing. By diversely organizing geometry of LC order, the mechanical response behaviors of LCH hydrogels are designed to exhibit localized deformations, steered cracking, and programmable swelling actuations. Our work offers a versatile avenue to scalably digital program LCH hydrogels in a high efficiency and accuracy. The digital designed hydrogel promises wide uses in actuators, bioscaffolds, biomimetic materials, and soft designer materials.

Supramolecular multilayer organization of chromosomes: possible functional roles of planar chromatin in gene expression and DNA replication and repair

Experimental evidence indicates that the chromatin filament is self-organized into a multilayer planar structure that is densely stacked in metaphase and unstacked in interphase. This chromatin organization is unexpected, but it is shown that diverse supramolecular assemblies, including dinoflagellate chromosomes, are multilayered. The mechanical strength of planar chromatin protects the genome integrity, even when double-strand breaks are produced. Here, it is hypothesized that the chromatin filament in the loops and topologically associating domains is folded within the thin layers of the multilaminar chromosomes. It is also proposed that multilayer chromatin has two states: inactive when layers are stacked and active when layers are unstacked. Importantly, the well-defined topology of planar chromatin may facilitate DNA replication without entanglements and DNA repair by homologous recombination.

The energy components of stacked chromatin layers explain the morphology, dimensions and mechanical properties of metaphase chromosomes

The measurement of the dimensions of metaphase chromosomes in different animal and plant karyotypes prepared in different laboratories indicates that chromatids have a great variety of sizes which are dependent on the amount of DNA that they contain. However, all chromatids are elongated cylinders that have relatively similar shape proportions (length to diameter ratio approx. 13). To explain this geometry, it is considered that chromosomes are self-organizing structures formed by stacked layers of planar chromatin and that the energy of nucleosome-nucleosome interactions between chromatin layers inside the chromatid is approximately 3.6 × 10(-20) J per nucleosome, which is the value reported by other authors for internucleosome interactions in chromatin fibres. Nucleosomes in the periphery of the chromatid are in contact with the medium; they cannot fully interact with bulk chromatin within layers and this generates a surface potential that destabilizes the structure. Chromatids are smooth cylinders because this morphology has a lower surface energy than structures having irregular surfaces. The elongated shape of chromatids can be explained if the destabilizing surface potential is higher in the telomeres (approx. 0.16 mJ m(-2)) than in the lateral surface (approx. 0.012 mJ m(-2)). The results obtained by other authors in experimental studies of chromosome mechanics have been used to test the proposed supramolecular structure. It is demonstrated quantitatively that internucleosome interactions between chromatin layers can justify the work required for elastic chromosome stretching (approx. 0.1 pJ for large chromosomes). The high amount of work (up to approx. 10 pJ) required for large chromosome extensions is probably absorbed by chromatin layers through a mechanism involving nucleosome unwrapping.