A structural dynamics model for how CPEB3 binding to SUMO2 can regulate translational control in dendritic spines

A prion-like RNA-binding protein, CPEB3, can regulate local translation in dendritic spines. CPEB3 monomers repress translation, whereas CPEB3 aggregates activate translation of its target mRNAs. However, the CPEB3 aggregates, as long-lasting prions, may raise the problem of unregulated translational activation. Here, we propose a computational model of the complex structure between CPEB3 RNA-binding domain (CPEB3-RBD) and small ubiquitin-like modifier protein 2 (SUMO2). Free energy calculations suggest that the allosteric effect of CPEB3-RBD/SUMO2 interaction can amplify the RNA-binding affinity of CPEB3. Combining with previous experimental observations on the SUMOylation mode of CPEB3, this model suggests an equilibrium shift of mRNA from binding to deSUMOylated CPEB3 aggregates to binding to SUMOylated CPEB3 monomers in basal synapses. This work shows how a burst of local translation in synapses can be silenced following a stimulation pulse, and explores the CPEB3/SUMO2 interplay underlying the structural change of synapses and the formation of long-term memories.

Thermodynamic analysis of Al clusters formation over aluminum melt

The formation of the aluminum nanoparticles with the size of up to 60 atoms in a gas phase is theoretically studied. Thermodynamic modeling has been applied to investigate the effect of the synthesis conditions on the distribution of the nanoparticles. The magic numbers of the particles have been estimated and found to be consistent with the available data. Furthermore, the simulations showed that higher amounts of larger nanoparticles are obtained during condensation from the supercooled aluminum vapor. In contrast, lower amounts of smaller clusters may be formed in a gas phase over the aluminum melt. Varying the temperature and concentration of supercooled aluminum vapor in a broad range results in no significant change in cluster size distribution. This effect is governed by the equilibrium shift.

Electrochemical and Molecular Assessment of Quinones as CO2-Binding Redox Molecules for Carbon Capture

The complexation and decomplexation of CO2 with a series of quinones of different basicity during electrochemical cycling in dimethylformamide solutions were studied systematically by cyclic voltammetry. In the absence of CO2, all quinones exhibited two well-separated reduction waves. For weakly complexing quinones, a positive shift in the second reduction wave was observed in the presence of CO2, corresponding to the dianion quinone-CO2 complex formation. The peak position and peak height of the first re-duction wave were unchanged, indicating no formation of complexes between the semiquinones and CO2. The relative heights of both reduction waves remained constant. In the case of strongly complexing quinones, the second reduction wave disappeared while the peak height of the first reduction wave approximately doubled, indicating that the two electrons transferred simultaneously at this potential. The observed voltammograms were rationalized through several equilibrium arguments. Both weakly and strongly complexing quinones underwent either stepwise or concerted mechanisms of oxidation and CO2 dissociation depending on the sweep rate in the cyclic voltammetric experiments. Relative to stepwise oxidation, the concerted process requires a more positive electrode potential to remove the electron from the carbonate complexes to release CO2 and regenerate the quinone. For weakly complexing quinones, the stepwise process corresponds to oxidation of the uncomplexed dianion and accompanying equilibrium shift, while for strongly complexing quinones the stepwise process would correspond to the oxidation of mono(carbonate) dianion to the complexed semiquinone and accompanying equilibrium shift. This study provides a mechanistic interpretation of the interactions that lead to the formation of quinone-CO2 complexes required for the potential development of an energy efficient electrochemical separation process and discusses important considerations for practical implementation of CO2 capture in the presence of oxygen with lower vapor pressure solvents.

Neutron Insights into Sorption Enhanced Methanol Catalysis

Sorption enhanced methanol production makes use of the equilibrium shift of the $$\hbox {CO}_2$$ CO 2 hydrogenation reaction towards the desired products. However, the increased complexity of the catalyst system leads to additional reactions and thus side products such as dimethyl ether, and complicates the analysis of the reaction mechanism. On the other hand, the unusually high concentration of intermediates and products in the sorbent facilitates the use of inelastic neutron scattering (INS) spectroscopy. Despite being a post-mortem method, the INS data revealed the change of the reaction path during sorption catalysis. Concretely, the experiments indicate that the varying water partial pressure due to the adsorption saturation of the zeolite sorbent influences the progress of the reaction steps in which water is involved. Experiments with model catalysts support the INS findings.

Mass fraction of fat, protein, and their ratio in Simmental breed cows’ milk

An important role in ensuring the taste and nutritional properties of milk belongs to its chemical composition, particularly the content of fat, protein, vitamins, and minerals. Numerous studies have confirmed the hypothesis of a close relationship between the proportion of milk fat and milk protein, which ideal ration is 1.1: 1.0 - 1.5: 1.0. It is this ratio that not only ensures the harmonious taste of the product but is also an indicator of a complete balanced feeding of animals. The studies were carried out in January - March 2021 at the breeding plant of the Simmental breed in the Tyumen region. The chemical composition of milk was determined in the laboratory for selection control of milk quality of the FSBEI of Higher Education “SAU of the Northern Trans-Urals”. The ratio between the mass fraction of fat and mass fraction of protein on average for the first three months of 2021 can be considered stable. In the milk of 20.0 - 27.8% of cows, there was a shift in equilibrium towards a decrease in butterfat content between the mass fraction of fat and mass fraction of protein, in turn, an increase in butterfat content relative to protein was noted in milk of 2.1 - 3.0% of cows. Equilibrium shift between butterfat and protein over 1.5: 1.0 suggests the risk of ketosis in the herd. In this regard, we recommend carrying out additional diagnostics on the content of ketone bodies in the blood and urine of cows during the milking period to confirm the presumptive diagnosis.

Conformational equilibrium shift underlies altered K+ channel gating as revealed by NMR

The potassium ion (K+) channel plays a fundamental role in controlling K+ permeation across the cell membrane and regulating cellular excitabilities. Mutations in the transmembrane pore reportedly affect the gating transitions of K+ channels, and are associated with the onset of neural disorders. However, due to the lack of structural and dynamic insights into the functions of K+ channels, the structural mechanism by which these mutations cause K+ channel dysfunctions remains elusive. Here, we used nuclear magnetic resonance spectroscopy to investigate the structural mechanism underlying the decreased K+-permeation caused by disease-related mutations, using the prokaryotic K+ channel KcsA. We demonstrated that the conformational equilibrium in the transmembrane region is shifted toward the non-conductive state with the closed intracellular K+-gate in the disease-related mutant. We also demonstrated that this equilibrium shift is attributable to the additional steric contacts in the open-conductive structure, which are evoked by the increased side-chain bulkiness of the residues lining the transmembrane helix. Our results suggest that the alteration in the conformational equilibrium of the intracellular K+-gate is one of the fundamental mechanisms underlying the dysfunctions of K+ channels caused by disease-related mutations.