Mechanistic Understanding of Additive Reductive Degradation and SEI Formation in High-Voltage NMC811||SiOx-Containing Cells via Operando ATR-FTIR Spectroscopy

The implementation of silicon (Si)-containing negative electrodes is widely discussed as an approach to increase the specific capacity of lithium-ion batteries. However, challenges caused by severe volume changes and continuous (re-)formation of the solid-electrolyte interphase (SEI) on Si need to be overcome. The volume changes lead to electrolyte consumption and active lithium loss, decaying the cell performance and cycle life. Herein, the additive 2-sulfobenzoic acid anhydride (2-SBA) is utilized as an SEI-forming electrolyte additive for SiO_x-containing anodes. The addition of 2-SBA to a state-of-the-art carbonate-based electrolyte in high-voltage LiNi_0.8Mn_0.1Co_0.1O₂, NMC811||artificial graphite +20% SiO_x pouch cells leads to improved electrochemical performance, resulting in a doubled cell cycle life. The origin of the enhanced cell performance is mechanistically investigated by developing an advanced experimental technique based on operando attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectroscopy. The operando ATR-FTIR spectroscopy results elucidate the degradation mechanism via anhydride ring-opening reactions after electrochemical reduction on the anode surface. Additionally, ion chromatography conductivity detection mass spectrometry, scanning electron microscopy, energy dispersive X-ray analysis, and quantum chemistry calculations are employed to further elucidate the working mechanisms of the additive and its degradation products.     

Expression of a P-glycoprotein gene is inducible in a multidrug-resistant human leukemia cell line

A human T lymphoblastoid CCRF-CEM cell line exhibiting cross resistance to a variety of drugs was selected with increasing doses of actinomycin D. A subline, designated CCRF ACTD400+, was permanently cultured in the presence of 400 ng/ml Actinomycin D for several months. Using a fragment of the human mdr1 cDNA we found high expression of a 5 kb mRNA species which was not detectable in the sensitive parental CCRF-CEM cell line. The extent of the mdr-mRNA expression in resistant cells, however, depended on the presence or absence of actinomycin D in the culture medium: when the inhibitor was omitted, the expression decreased to about 60% after one month. In reverse, the steady state level of the P-glycoprotein mRNA increased about 2.5-fold within 72 h after the original dose of the drug was added again. In further experiments we recorded the actinomycin D or adriamycin dose response curves of the variously treated sublines by evaluation of [3H]uridine or [3H]thymidine incorporation, respectively, into acid insoluble material. Consistently, the drug sensitivity of the respective macromolecular synthesis was found to decrease with increasing mdr-mRNA levels.     

Saltaties bij Schimmels door

Antonie van Leeuwenhoek -     

On the transport of tripeptide antibiotics in bacteria.

The two tripeptide antibiotics L-2-amino-4-methylphosphinobutyryl-alanyl-alanyl-alanine (L-phosphinothricyl-alanyl-alanine) and L-(N5-phosphono)methionine-S-sulfoximinyl-alanyl-alanine, both inhibitors of the glutamine synthetase, are transported into the cell of Escherichia coli K 12 via the oligopeptide transport system. The uptake by this system is proved first of all by cross-resistance with tri-L-ornithine using oligopeptide-transport-deficient mutants, and secondly by antagonism tests demonstrating competitive reversal of the action of the antibiotic by several peptides which have been shown to be transported via the oligopeptide transport system, e.g. tri-L-alanine, tetra-L-alanine, tri-L-lysine, tri-L-serine, tri-glycine, glycyl-glycyl-L-alanine and the synthetic tripeptide L-azadenyl-aminohexanoyl-alanyl-alanine. On the other hand, there is no effect on the action of the antibiotic in antagonism tests with compounds which use different transport systems, such as L-alanyl-alanine, L-lysyl-lysine, glutathione and the synthetic amino acid azaadenylaminohexanoic acid, i.e. 2-amino-6-(7-amino-3H-v-triazolo-[4,5-d]-pyrimidin-3-yl)hexanoic acid. Another inhibitor of the glutamine synthetase, L-methionine-S-dioxide (methioninesulfone) could be converted into a tripeptide form by linkage to L-alanyl-alanine analogously to the tripeptide antibiotics described above. Whereas the free L-methionine-S-dioxide seems to be transported via the methionine transport system, the tripeptide form is transported via the oligopeptide transport system. Thus, this glutamine synthetase inhibitor can be taken up by the cell via two different transport mechanisms. Our results indicate that this could provide a synergistic effect. The syntheses of the new tripeptides L-azaadenylaminohexanoyl-alanyl-alanine and L-methionine-S-dioxidyl-alanyl-alanine were performed by dicyclohexylcarbodiimide couplings of the unusual N-protected L-alpha-amino acids azaadenylaminohexanoic acid and L-methionine-S-dioxide to L-alanyl-alanine-tert-butyl ester followed by common deprotection steps. Tri-L-ornithine was synthesized without carboxyl protection via two successive couplings of hydroxybenzotriazol esters of Nalpha-butoxycarbonyl-Ndelta-benzyloxycarbonyl-L-ornithine.     

A temperature shock can lead to trans‐generational immune priming in the Red Flour Beetle,Tribolium castaneum

Trans‐generational immune priming (TGIP) describes the transfer of immune stimulation to the next generation. As stress and immunity are closely connected, we here address the question whether trans‐generational effects on immunity and resistance can also be elicited by a nonpathogen stress treatment of parents. General stressors have been shown to induce immunity to pathogens within individuals. However, to our knowledge, it is as of yet unknown whether stress can also induce trans‐generational effects on immunity and resistance. We exposed a parental generation (mothers, fathers, or both parents) of the red flour beetle Tribolium castaneum, a species where TGIP has been previously been demonstrated, to either a brief heat or cold shock and examined offspring survival after bacterial infection with the entomopathogen Bacillus thuringiensis. We also studied phenoloxidase activity, a key enzyme of the insect innate immune system that has previously been demonstrated to be up‐regulated upon TGIP. We quantified parental fecundity and offspring developmental time to evaluate whether trans‐generational priming might have costs. Offspring resistance was found to be significantly increased when both parents received a cold shock. Offspring phenoloxidase activity was also higher when mothers or both parents were cold‐shocked. By contrast, parental heat shock reduced offspring phenoloxidase activity. Moreover, parental cold or heat shock delayed offspring development. In sum, we conclude that trans‐generational priming for resistance could not only be elicited by pathogens or pathogen‐derived components, but also by more general cues that are indicative of a stressful environment. The interaction between stress responses and the immune system might play an important role also for trans‐generational effects.     

Coordinating Anions “to the Rescue” of the Lithium Ion Mobility in Ternary Solid Polymer Electrolytes Plasticized With Ionic Liquids

Lithium salts with low coordinating anions such as bis(trifluoromethanesulfonyl)imide (TFSI) have been the state-of-the-art for polyethylene oxide (PEO)-based “dry” polymer electrolytes for 3 decades. Plasticizing PEO with TFSI-based ionic liquids (ILs) to form ternary solid polymer electrolytes (TSPEs) increases conductivity and Li⁺ diffusivity. However, the Li⁺ transport mechanism is unaffected compared to their “dry” counterparts and is essentially coupled to the dynamics of the polymer host matrix, which limits Li⁺ transport improvement. Thus, a paradigm shift is hereby suggested: the utilization of more coordinating anions such as trifluoromethanesulfonyl-N-cyanoamide (TFSAM), able to compete with PEO for Li⁺ solvation, to accelerate the Li⁺ transport and reach a higher Li⁺ transference number. The Li–TFSAM interaction in binary and ternary TFSAM-based electrolytes is probed by experimental methods and discussed in the context of recent computational results. In PEO-based TSPEs, TFSAM drastically accelerates the Li⁺ transport (increases Li⁺ transference number by a factor 6 and the Li⁺ conductivity by 2–3) and computer simulations reveal that lithium dynamics are effectively re-coupled from polymer to anion dynamics. Last, this concept of coordinating anions in TSPEs is successfully applied in LFP||Li metal cells leading to enhanced capacity retention (86% after 300 cycles) and an improved rate performance at 2C.