Nucleosomes are elementary building blocks of chromatin in eukaryotes. They tightly wrap ∼147 DNA base pairs around an octamer of histone proteins. How nucleosome structural dynamics affect genome functioning is not completely clear. Here we report all-atom molecular dynamics simulations of nucleosome core particles at a timescale of 15 microseconds. At this timescale, functional modes of nucleosome dynamics such as spontaneous nucleosomal DNA breathing, unwrapping, twisting, and sliding were observed. We identified atomistic mechanisms of these processes by analyzing the accompanying structural rearrangements of the histone octamer and histone-DNA contacts. Octamer dynamics and plasticity were found to enable DNA unwrapping and sliding. Through multi-scale modeling, we showed that nucleosomal DNA dynamics contribute to significant conformational variability of the chromatin fiber at the supranucleosomal level. Our study further supports mechanistic coupling between fine details of histone dynamics and chromatin functioning, provides a framework for understanding the effects of various chromatin modifications.

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Smart thermoresponsive gels and cryogels with incorporated emulsions have been synthesized and studied. The gels were obtained by three-dimensional copolymerization of N-isopropylacrylamide and N,N'-methylene-bis-acrylamide or N,N'-bis(acryloyl)cystamine in the presence of dispersion of tetradecane stabilized with sodium dodecylsulfate. Polymerization was performed at room temperature and below the water crystallization temperature. Both composite gels and cryogels were capable of heat-induced collapse. The extent of the collapse of the composite gel prepared at room temperature was much smaller and without squeezing of the lipophilic phase out of the shrunk composite gel. In contrast, shrinking of the composite cryogel was accompanied by release of tetradecane emulsion.

Summary: “Swiss‐cheese” polyelectrolyte gels, i.e., gels containing isolated voids filled with water were synthesized and studied. The gels were obtained by three‐dimensional copolymerization of neutral and charged monomers in the presence of oil/water emulsion stabilized by ionic surfactant. After removal of the surfactant and droplets of oil from the gel, the latter contains voids surrounded with charged swollen polymer network. Experiments were performed with slightly cross‐linked gels of copolymers of sodium‐2‐acrylamide‐2‐methyl‐1‐propanesulfonate with acrylamide. The gel containing voids absorbs much more anionic dyes than the control gel with the same chemical composition of the network obtained in homogeneous solution. This effect is due to strongly inhomogeneous distribution of the low molecular weight anions between the voids and the anionic matrix of the gel. The study of diffusion of the dyes in the gels with and without voids and of the kinetics of their swelling and collapse shows that the voids in the gel are isolated.