Performance and durability of solid oxide cell (SOC) electrodes are closely linked to their microstructure properties. Thus, the comprehensive characterization of 3D microstructures e.g., obtained by FIB-SEM tomography is essential...

We report a general route for synthesizing ortho-substituted unsymmetrical biphenyl and polyaromatic s-aryltetrazines. These compounds are inaccessible by classical Pinner hydrazine condensation or by the current s-aryltetrazine aromatic core functionalization methods described up to now. We exploited multiple versatile N-directed palladium C–H activation/halogenation of s-aryltetrazine to form C–X bonds (X = I, Br, Cl, F), which collectively produced polyhalogenated unsymmetrical building blocks. We achieved a sequence of selective C–H halogenation reactions in a specific order to produce reactive aryl halides. Polyhalogenated s-aryltetrazines can then be used for controlled cross-coupling reactions toward ortho-substituted polyaromatic s-aryltetrazines. In general, this C–H functionalization route gives access to a large number of variously halogenated building blocks practical for further synthetic implementation of tetrazines (arylation, cycloaddition, etc.). Herein, we exemplified their potential by using halogen-selective Suzuki–Miyaura reactions for divergent construction of novel biphenyl s-tetrazines. Therefore, we deliver original poly­(hetero)­aromatic tetrazine structures, such as new typically “Z-shaped” and “T-shaped” species. We examined by DFT calculation the origin of the remarkable regioselectivity in some C–H concurrent halogenation reactions. Computations focused at free enthalpy profiles for C–H activation of aryltetrazines to form the intermediate palladacycles by CMD process. We showed that the presence of halogen substituents on aryl groups before further halogenation increases the activation barrier to form the determining C–H activation intermediate palladacycle. XRD studies of functionalized tetrazines evidenced planarity ruptures in the mutual arrangement of aromatic cycles. Finally, this methodology allowed us to deliver a unique tetrahalogenated s‑aryltetrazine holding not less than four different halogens arranged in ortho-aryl positions.

Silencing of tissue-specific gene expression in mammalian somatic cell hybrids is a well-documented epigenetic phenomenon which is both profound (involving a large number of genes) and enigmatic. Our aim was to utilize whole-genome microarray analyses to determine the true extent of gene silencing on a genomic level. By comparing gene expression profiles of hepatoma×fibroblast cell hybrids with those of parental cells, we have identified over 300 liver-enriched genes that are repressed at least 5-fold in the cell hybrids, the majority of which are repressed at least 10-fold. Also, we identify nearly 200 fibroblast-enriched genes that are repressed at least 5-fold. Silenced hepatic genes include several that encode transcription factors and proteins involved in signal transduction pathways. These data suggest that extensive reprogramming occurs in cell hybrids, leading to a nearly global (although not complete) loss of tissue-specific gene expression.

No abstract

No abstract