Dramatic Drop in Cell Resistance through Induced Dipoles and Bipolar Electrochemistry

The use of slurries of conducting particles has been considered a way to extend the electrode area in some energy storage electrochemical cells. When suspensions of conducting particles are used in electrolytes a decreased impedance is observed, even for concentrations much lower than the theoretical percolation limits. Indeed, it is known that polarization occurs when a conducting material is immersed in an electrolyte in presence of electric fields, and bipolar electrochemistry processes may occur. This work demonstrates the dramatic drop in resistance for electrochemical cells with just a few macroscopic conducting pieces immersed in the electrolyte, in the absence of any electrical contact, through bipolar induction. Furthermore, mediation of soluble redox species between adjacent induced poles of opposite charge results in an additional mechanism for charge transfer, contributing further to the decrease in impedance. Relevant parameters like size, geometry, and spatial occupation of inducible pieces within the electric field, are relevant. Remarkably, the effects observed can explain some empirical observations previously reported for carbon suspensions and slurries. Thus, no electronic percolation requiring particle contact, nor ordering, are needed to explain the good performance associated to lowered impedance These results suggest new engineering designs for electrochemical cells with enhanced currents

The C50 carotenoid bacterioruberin regulates membrane fluidity in pink-pigmented Arthrobacter species

Carotenoids have several crucial biological functions and are part of the cold adaptation mechanism of some bacteria. Some pink-pigmented Arthrobacter species produce the rare C50 carotenoid bacterioruberin, whose function in these bacteria is unclear and is found mainly in halophilic archaea. Strains Arthrobacter agilis DSM 20550T and Arthrobacter bussei DSM 109896T show an increased bacterioruberin content if growth temperature is reduced from 30 down to 10 °C. In vivo anisotropy measurements with trimethylammonium-diphenylhexatriene showed increased membrane fluidity and a broadening phase transition with increased bacterioruberin content in the membrane at low-temperature growth. Suppression of bacterioruberin synthesis at 10 °C using sodium chloride confirmed the function of bacterioruberin in modulating membrane fluidity. Increased bacterioruberin content also correlated with increased cell resistance to freeze–thaw stress. These findings confirmed the adaptive function of bacterioruberin for growth at low temperatures for pink-pigmented Arthrobacter species.

KDM6B promotes activation of the oncogenic CDK4/6-pRB-E2F pathway by maintaining enhancer activity in MYCN-amplified neuroblastoma

The H3K27me2/me3 histone demethylase KDM6B is essential to neuroblastoma cell survival. However, the mechanism of KDM6B action remains poorly defined. We demonstrate that inhibition of KDM6B activity 1) reduces the chromatin accessibility of E2F target genes and MYCN, 2) selectively leads to an increase of H3K27me3 but a decrease of the enhancer mark H3K4me1 at the CTCF and BORIS binding sites, which may, consequently, disrupt the long-range chromatin interaction of MYCN and E2F target genes, and 3) phenocopies the transcriptome induced by the specific CDK4/6 inhibitor palbociclib. Overexpression of CDK4/6 or Rb1 knockout confers neuroblastoma cell resistance to both palbociclib and the KDM6 inhibitor GSK-J4. These data indicate that KDM6B promotes an oncogenic CDK4/6-pRB-E2F pathway in neuroblastoma cells via H3K27me3-dependent enhancer-promoter interactions, providing a rationale to target KDM6B for high-risk neuroblastoma.

N -glycosylation of a cargo protein C-terminal domain recognized by the type IX secretion system in Cytophaga hutchinsonii affects protein secretion and localization

Cytophaga hutchinsonii is a Gram-negative bacterium belonging to the phylum Bacteroidetes . It digests crystalline cellulose with an unknown mechanism, and possesses a type IX secretion system (T9SS) that can recognize the C-terminal domain (CTD) of the cargo protein as a signal. In this study, the functions of CTD in the secretion and localization of T9SS substrates in C. hutchinsonii were studied by fusing the green fluorescent protein (GFP) with CTD from CHU_2708. CTD is necessary for the secretion of GFP by C. hutchinsonii T9SS. The GFP-CTD CHU_2708 fusion protein was found to be glycosylated in the periplasm with a molecular mass about 5 kDa higher than that predicted from its sequence. The glycosylated protein was sensitive to peptide- N -glycosidase F which can hydrolyze N -linked oligosaccharides. Analyses of mutants obtained by site-directed mutagenesis of asparagine residues in the N-X-S/T motif of CTD CHU_2708 suggest that N -glycosylation occurred on the CTD. CTD N- glycosylation is important for the secretion and localization of GFP-CTD recombinant proteins in C. hutchinsonii . Glycosyltransferase encoding gene chu_3842 , a homologous gene of Campylobacter jejuni pglA , was found to participate in the N -glycosylation of C. hutchinsonii . Deletion of chu_3842 affected cell motility, cellulose degradation, and cell resistance to some chemicals. Our study provided the evidence that CTD as the signal of T9SS was N -glycosylated in the periplasm of C. hutchinsonii . IMPORTANCE The bacterial N -glycosylation system has previously only been found in several species of Proteobacteria and Campylobacterota , and the role of N -linked glycans in bacteria is still not fully understood. C. hutchinsonii has a unique cell-contact cellulose degradation mechanism, and many cell surface proteins including cellulases are secreted by the T9SS. Here, we found that C. hutchinsonii , a member of the phylum Bacteroidetes , has an N -glycosylation system. Glycosyltransferase CHU_3842 was found to participate in the N -glycosylation of C. hutchinsonii proteins, and had effects on cell resistance to some chemicals, cell motility, and cellulose degradation. Moreover, N -glycosylation occurs on the CTD translocation signal of T9SS. The glycosylation of CTD apears to play an important role in affecting T9SS substrates transportation and localization. This study enriched our understanding of the widespread existence and multiple biological roles of N -glycosylation in bacteria.

Protein- and Cell-Resistance of Zwitterionic Peptide-Based Self-Assembled Monolayers: Anti-Biofouling Tests and Surface Force Analysis

Peptide-based self-assembled monolayers (peptide-SAMs) with specific zwitterionic amino acid sequences express an anti-biofouling property. In this work, we performed protein adsorption and cell adhesion tests using peptide-SAMs with repeating units of various zwitterionic pairs of amino acids (EK, DK, ER, and DR). The SAMs with the repeating units of EK and DK (EK and DK SAMs) manifested excellent bioinertness, whereas the SAMs with the repeating units of ER and DR (ER and DR SAMs) adhered proteins and cells. We also performed surface force measurements using atomic force microscopy to elucidate the mechanism underlying the difference in the anti-biofouling property. Our measurements revealed that water-induced repulsion with a range of about 8 nm acts between EK SAMs (immobilized on both probe and substrate) and DK SAMs, whereas such repulsion was not observed for ER and DR SAMs. The strength of the repulsion exhibited a clear correlation with the protein- and cell-resistance of the SAMs, indicating that the interfacial water in the vicinity of EK and DK SAMs is considered as a physical barrier to deter protein and cells from their adsorption or adhesion. The range of the repulsion observed for EK and DK SAMs is longer than 8 nm, indicating that the hydrogen bonding state of the interfacial water with a thickness of 4 nm is modified by EK and DK SAMs, resulting in the expression of the anti-biofouling property.

Giant cell glioblastoma in childhood-Pathohistological and immunohistochemical analysis, forecast and complex treatment

A six year old child is presented with giant cell glioblastoma multiforme. The importance of pathohistological and immunohistochemical analysis is discussed for the diagnosis of this rare pathohistological subtype glioblastoma in childhood. The Magnetic Resonance Image Characteristics, unfavorable prognosis and high cancer cell resistance to radiotherapy (RT) and chemotherapy (Ch) are also highlighted. The risk of local recurrences and tumor progression is high, despite the complex treatment, including visibly total tumor surgery, postoperative RT and adjuvant Ch. By this pediatric clinical case of childhood giant cell glioblastoma multiforme, we emphasize the emerging need to optimize early diagnostics and the multidisciplinary healing approach.