Study of the surface properties of glauconite

The acid-base properties of the glauconite surface has been studied by potentiometric titration. Using a surface complexation model with a constant exchange capacity, it was shown that positively charged surface centers and exchange centers dominate in the acidic pH region, and negatively charged centers dominate in the neutral and alkaline regions. The corresponding constants of acid-base equilibrium have been calculated. The data obtained were used to study the sorption of cadmium and lead on glauconite.

DUAL FUNCTION OF ZIKA VIRUS NS2B-NS3 PROTEASE

Zika virus (ZIKV) serine protease, indispensable for viral polyprotein processing and replication, is composed of an NS2B polypeptide that associates with a proteolytic N terminal fragment of NS3 polypeptide (NS3pro) to form NS2B-NS3pro. The larger C-terminal fragment of NS3 polypeptide contains helicase activity. In the present study, we discovered that ZIKV NS2BNS3pro efficiently binds single-stranded (ss) RNA (Kd ~0.3 uM), suggesting that the protease may have a novel function. We tested an array of NS2B-NS3pro modifications and found that NS2B NS3pro constructs that adopt the recently discovered super-open conformation could not bind ssRNA. Likewise, stabilization of NS2B-NS3pro in the closed (proteolytically active) conformation by substrate-like inhibitors abolished ssRNA binding. Therefore, we suggest that ssRNA binding occurs when ZIKV protease adopts the open conformation, which could be modeled using dengue NS2B-NS3pro in the open conformation. ssRNA binding competes with ZIKV NS2B-NS3pro protease activity, likely by shifting the complex into the open conformation. Modeling of ZIKV NS3 helicase activity based on homologous crystal structures suggests that the open conformation of NS3pro domains provides a positively charged surface contiguous with the NS3 helicase domain. Such a positively charged surface is well poised to bind ssRNA, providing an explanation for the previously observed requirement of NS3pro for RNA processivity by viral helicase. Our structure-function analyses suggest that binding of ssRNA by the protease domain of NS3 is likely to be a universal feature of Flaviviridae, given the high level of homology between NS3 protease-helicase proteins in this family.

Structural basis of soluble membrane attack complex packaging for clearance

Unregulated complement activation causes inflammatory and immunological pathologies with consequences for human disease. To prevent bystander damage during an immune response, extracellular chaperones (clusterin and vitronectin) capture and clear soluble precursors to the membrane attack complex (sMAC). However, how these chaperones block further polymerization of MAC and prevent the complex from binding target membranes remains unclear. Here, we address that question by combining cryo electron microscopy (cryoEM) and cross-linking mass spectrometry (XL-MS) to solve the structure of sMAC. Together our data reveal how clusterin recognizes and inhibits polymerizing complement proteins by binding a negatively charged surface of sMAC. Furthermore, we show that the pore-forming C9 protein is trapped in an intermediate conformation whereby only one of its two transmembrane β-hairpins has unfurled. This structure provides molecular details for immune pore formation and helps explain a complement control mechanism that has potential implications for how cell clearance pathways mediate immune homeostasis.

Adsorption phenomena at the interface between mercury and solutions containing choline chloride, ethylene glycol and water

Adsorption of the components of deep eutectic solvent ethaline (ethylene glycol and choline chloride) on mercury electrode is investigated by electrocapillary measurements. It is determined that choline cations are mainly adsorbed on the negatively charged surface of mercury, while chloride anions are mainly adsorbed on the positively charged surface. The corresponding values of free energies of adsorption and interactions of adsorbate and solvent with metal are calculated and analyzed. An anomalous increase in both the apparent value of the adsorption at limiting coverage and the free energy of the interaction of the choline cation with mercury is observed in the transition from aqueous to ethylene glycol solutions, which is explained by the formation of complexes in a surface layer that exist in deep eutectic solvents and are capable of adsorbing on the electrode surface. The free energy of interaction with the mercury surface is higher than the energy of squeezing out from the volume of the solution onto its surface, which indicates the specific interaction of the adsorbate with mercury. A marked decrease in interfacial tension on both branches of the electrocapillary curve is observed when water is added to ethaline.

Development of Gelatin-Coated Microspheres for Novel Bioink Design

A major challenge in tissue engineering is the formation of vasculature in tissue and organs. Recent studies have shown that positively charged microspheres promote vascularization, while also supporting the controlled release of bioactive molecules. This study investigated the development of gelatin-coated pectin microspheres for incorporation into a novel bioink. Electrospray was used to produce the microspheres. The process was optimized using Design-Expert® software. Microspheres underwent gelatin coating and EDC catalysis modifications. The results showed that the concentration of pectin solution impacted roundness and uniformity primarily, while flow rate affected size most significantly. The optimal gelatin concentration for microsphere coating was determined to be 0.75%, and gelatin coating led to a positively charged surface. When incorporated into bioink, the microspheres did not significantly alter viscosity, and they distributed evenly in bioink. These microspheres show great promise for incorporation into bioink for tissue engineering applications.

On the Peculiarities of Realization of Electrostatic Instability of Charged Liquid Surface in Various Geometries

The paper deals with some peculiarities of realization of electrostatic instability of a charged liquid surface on the vertices of the charged and uncharged drops in an external electrostatic field in a cylindrical jet and a flat surface. It was shown that the critical values of the surface density of the electric charge under the mentioned conditions on the threshold of the realization of instability are different in magnitude, despite the phenomenological similarity. Most probably, the reason is the differences (under all mentioned conditions) in the spatial change in the strength of the electrostatic field in the vicinity of the growing (when the charged surface of the liquid is unstable) emission protrusion. Both equilibrium and non-equilibrium forms of droplets, jets, planes and their symmetry were discussed.