Addition Of Ca2 Research Articles

Glutamate-Evoked Ca2+ Responses in the Rat Suprachiasmatic Nucleus: Involvement of Na+/K+-ATPase and Na+/Ca2+-Exchanger.

Glutamate mediates photic entrainment of the central clock in the suprachiasmatic nucleus (SCN) by evoking intracellular Ca2+ signaling mechanisms. However, the detailed mechanisms of glutamate-evoked Ca2+ signals are not entirely clear. Here, we used a ratiometric Ca2+ and Na+ imaging technique to investigate glutamate-evoked Ca2+ responses. The comparison of Ca2+ responses to glutamate (100 μM) and high (20 mM) K+ solution indicated slower Ca2+ clearance, along with rebound Ca2+ suppression for glutamate-evoked Ca2+ transients. Increasing the length of exposure time in glutamate, but not in 20 mM K+, slowed Ca2+ clearance and increased rebound Ca2+ suppression, a result correlated with glutamate-induced Na+ loads. The rebound Ca2+ suppression was abolished by ouabain, monensin, Na+-free solution, or nimodipine, suggesting an origin of activated Na+/K+-ATPase (NKA) by glutamate-induced Na+ loads. Ouabain or Na+-free solution also slowed Ca2+ clearance, apparently by retarding Na+/Ca2+-exchanger (NCX)-mediated Ca2+ extrusion. Together, our results indicated the involvement of glutamate-induced Na+ loads, NKA, and NCX in shaping the Ca2+ response to glutamate. Nevertheless, in the absence of external Na+ (NMDG substituted), Ca2+ clearance was still slower for the Ca2+ response to glutamate than for 20 mM K+, suggesting participation of additional Ca2+ handlers to the slower Ca2+ clearance under this condition.

Improving the chloride binding capacity of alkali activated slag by calcium and aluminum enriched minerals

In this paper, a modified alkali activated slag with improved chloride binding capacity is proposed by introducing calcium and aluminum enriched phases in the binding system. The Ca and Al phases are added in order to promote the formation of AFm type phases in alkali activated system and then transformed into Friedel's salt (Fs) when in contact with chloride. The effects of calcium and alumina type on phase composition, chloride binding behavior, mechanical property of modified alkali activated slag binders are discussed. The results show that the addition of Ca and Al enriched minerals effectively improve the chloride binding capacity of the binder up to 44.4%. The combination of calcium hydroxide and metakaolin shows the highest binding efficiency, followed by calcium nitrite and cement. Metakaolin exhibits better modification on chloride binding capacity than nano alumina. The incorporation of Ca and Al enriched minerals together successfully promotes the formation of AFm type phases (Mc and AFm-NO2) in alkali activated system, while the addition of metakaolin increases the reaction degree and the mean chain length of C-(A)-S-H gels, contributing to the chloride binding capacity. The mechanical properties of alkali activated slag are also improved by adding calcium hydroxide, cement, and alumina enriched minerals, while calcium nitrite exhibits a slight negative effect.

Calcium‐Modified PtSn/Al2O3 Catalyst for Propane Dehydrogenation with High Activity and Stability

AbstractCatalytic dehydrogenation of propane to propylene and by‐product hydrogen is an atom‐economical and environmentally friendly route. PtSn/Al2O3 catalysts have been industrialized in this process, but still suffer from platinum sintering and coke deposition under reaction conditions. Herein, we design a calcium‐modified PtSn/Al2O3 catalyst showing a superior propane dehydrogenation performance. The presence of calcium combined with unsaturated aluminum and tin could consist of a new local microenvironment that promotes the dispersion of the platinum species and increases the electron density of the platinum species, which improves the catalytic activity, facilitates propylene desorption and inhibits coke formation. As a result, the achieved PtSnCa/Al2O3 catalyst exhibits a higher propylene formation rate and a lower coke‐accumulation rate compared to the catalyst without Ca addition. Moreover, the size of active phase clusters (∼1 nm) remained almost unchanged after the catalytic test, indicating a superior sintering resistance.

Modification Effect of Ca(OH)2 on the Carbonation Resistance of Fly Ash-Metakaolin-Based Geopolymer

Compared with Portland cement, geopolymers have poor carbonization resistance, which will greatly limit the application their application. To improve the carbonization resistance of geopolymers, firstly, the carbonization behavior of the fly ash-metakaolin-based geopolymer was studied through accelerated carbonization tests. Secondly, different amounts of Ca(OH)2 were introduced into the composite system, and the modification effect of the carbonization resistance of the modified geopolymer was studied. Finally, the modification effect of Ca(OH)2 on the fly ash-metakaolin-based geopolymers was analyzed, and the modification mechanism was explored. It was found that adding Ca(OH)2 to the fly ash-metakaolin-based geopolymer could significantly improve its initial compressive strength, but its strength after carbonization remained basically unchanged; meanwhile, the compressive strength of the terpolymer after carbonization clearly decreased after adding Ca(OH)2. Compared with ordinary Portland cement, the carbonization rate of fly ash-metakaolin-based geopolymer is faster, and the addition of Ca(OH)2 can inhibit the development of its carbonization depth. With increased carbonization age, the alkalinity of the geopolymer decreased, and the addition of Ca(OH)2 inhibited the decrease in the alkalinity of the geopolymer. The addition of Ca(OH)2 improved the microstructure of the geopolymers, the pore structure became denser, and the pore size became smaller size after carbonization. The hydration products of fly ash-metakaolin-based geopolymer are mainly amorphous silicaluminate gel and C-S-H gel, and Ca(OH)2 forms in the hydration products of terpolymer with the incorporation of Ca(OH)2, which is conducive to improving the carbonization resistance. In summary, Ca(OH)2 can play a good role in modifying the carbonization resistance of fly ash-metakaolin-based geopolymers.

Influence of key cations and anions on phosphate removal by Fe(0) electrocoagulation

The electrocoagulation technology is efficient for the removal of phosphate. The removal efficiency of phosphate in the secondary effluent is higher than that of in the synthetic wastewater. In order to identify the key factors for promoting the removal of phosphate in Fe(0) electrocoagulation (EC), this study investigated typical coexisted substances in the secondary effluent, including Ca2+, Mg2+, NH4+, HCO3−, SO42−. The results indicated that Ca2+ and Mg2+ were the key factors promoting the removal of phosphate by Fe(0) EC both under normal (5–6 mg/L) and low dissolved oxygen (DO) (≤ 1 mg/L) conditions. Under low and normal DO conditions, the phosphate removal efficiency increased from 28 % to 98 % ± 2 % (in 5 min) at 10 mA/cm2 with the addition of Ca2+ (0.2–20 mM) or Mg2+ (0.2–2 mM) but decreased to approximately 70 % with the addition of a Mg2+ of 20 mM. Under low and normal DO conditions, the aggregation time of iron oxide flocs decreased from 10 min to 5 min when the concentration of Ca2+ increased from 0 to 20 mM and Mg2+ increased from 0 to 2 mM. The aggregation stability of flocs was not sufficient when the Mg2+ concentration was 20 mM at 5 mA/cm2. Our results confirmed that Fe(0) EC was suitable for the removal of phosphate in the secondary effluent, especially containing moderate amounts of Ca2+ and Mg2+ regardless of the concentration of DO.

Black Tea Extracts/Polyvinyl Alcohol Active Nanofibers Electrospun Mats with Sustained Release of Polyphenols for Food Packaging Applications

The efficiency in the capabilities to store and release antioxidants depends on the film morphology and its manufacturing process, as well as on the type and methodology used to obtain the polyphenol extracts. Here, hydroalcoholic extracts of black tea polyphenols (BT) were obtained and dropped onto different polyvinyl alcohol (PVA) aqueous solutions (water or BT aqueous extract with and without citric acid, CA) to obtain three unusual PVA electrospun mats containing polyphenol nanoparticles within their nanofibers. It was shown that the mat obtained through the nanoparticles precipitated in BT aqueous extract PVA solution presented the highest total polyphenol content and antioxidant activity, and that the addition of CA as an esterifier or PVA crosslinker interfered with the polyphenols. The release kinetics in different food simulants (hydrophilic, lipophilic and acidic) were fitted using Fick's diffusion law and Peppas' and Weibull's models, showing that polymer chain relaxation is the main mechanism in all food simulants except for the acidic, which presented an abrupt release by Fick's diffusion mechanism of about 60% before being controlled. This research provides a strategy for the development of promising controlled-release materials for active food packaging, mainly for hydrophilic and acidic food products.

Removal of Arsenate from Contaminated Water via Combined Addition of Magnesium-Based and Calcium-Based Adsorbents

The effects of the combined addition of Mg- and Ca-based adsorbents (MgO, Mg(OH)2, MgCO3, CaO, Ca(OH)2, and CaCO3) were systematically tested for improving arsenic-removal performance and inhibiting the leaching of base material components from the adsorbent. Arsenic-removal tests were conducted with each single type or combination of two types of adsorbents. Results obtained after the combined-addition tests were compared with those obtained from the single-addition test with each adsorbent. The arsenic-removal performance improved in most combined additions but decreased in certain combined additions of MgO or Mg(OH)2 with Ca-based adsorbents. The arsenic-removal performance of the combined addition of MgCO3 and Ca(OH)2 was the highest. The combination of Mg-based adsorbents with CaO or Ca(OH)2 inhibited Mg-leaching, whereas that of CaO or Ca(OH)2 with MgCO3 inhibited Ca-leaching. Improvement in arsenic-removal performance for the combination of MgCO3 with CaO or Ca(OH)2 was caused by the incorporation and co-precipitation with arsenic when Mg(OH)2 and CaCO3 were produced. MgCO3-Ca(OH)2 and MgCO3-CaO are recommended for both arsenic removal and environmental adsorbent stability that can be effectively applied over a wide range of arsenic concentrations.

Positive effect of Ca addition on the risk of Cu and Zn in digestate as biofertilizer

The addition of Ca in anaerobic digestion will passivate the heavy metals in digestate. The effects of CaCl2, Ca(OH)2 and CaCO3 addition on the anaerobic digestion process and the speciation changes of Cu and Zn in solid fraction of anaerobic digestate (SFD) after digestion were studied. Then the effects of Ca-containing solid fraction digestate (SFD-Ca) application on the speciation changes of Cu and Zn in soil and the effects of ryegrass on the enrichment of Cu and Zn were also explored through pot experiments. The results indicated that: The addition of Ca(OH)2 was beneficial to the transfer of Cu and Zn from the liquid fraction of anaerobic digestate (LFD) to SFD, and the transfer effect was the best. The transfer amount of Cu and Zn increased by about 10.0% and 4.2%, respectively, compared with the blank group. The SFD-Ca promoted the increase of biomass, inhibited the enrichment of Cu and Zn by ryegrass, and the effect of a high concentration of Ca(OH)2 was the best. Ryegrass biomass increased by 19.7%, and the enrichment of Cu and Zn decreased by 39.3% and 31.1%, respectively. High concentration of Ca(OH)2-containing solid fraction digestate (SFD-Ca(OH)2) had the best passivation effect on Cu and Zn in soil, the residual state of Cu and Zn in soil increased by 4.3% and 7.8%, respectively. Adding a high concentration of Ca(OH)2 had a positive effect on ryegrass biomass and reduced the risk of Cu and Zn when SFD was used as biofertilizer.

Effect of Ca Addition on Mechanical Properties and the Ignition Temperature of Cast WE43 alloys

Effect of Ca Addition on Mechanical Properties and the Ignition Temperature of Cast WE43 alloys

Effect of Ca addition on the microstructure and creep behaviour of AZ91 Mg alloy

The lower density and higher specific mechanical properties of the magnesium and its alloys are attracting the great attention of the automakers from the perspective of automobile fuel economy and reducing the environmental impact. The AZ91 magnesium alloy has excellent mechanical properties; however, its application is limited by its poor creep resistance. In the present study, the effect of Ca addition and squeeze casting on the microstructure and creep behaviour of AZ91 Mg alloy has been investigated. Tensile creep test is conducted at temperatures of 150 and 175 °C under 50 MPa stress. The study shows an increase in creep resistance with Ca addition. Microstructural investigations with scanning electron microscopy confirm that the precipitation of thermally stable Al2Ca phase with skeleton morphology leads to increased creep resistance.

Issue Information

Front cover Calcium-permeable AMPA receptors (CP-AMPARs) are involved in synaptogenesis and formation of neuronal circuitry. However, these receptors provide additional Ca2+ inflow into neurons, contributing dysregulation of Ca2+ homeostasis and neuronal dysfunction in excitotoxicity associated with numerous CNS disorders. Considering these aspects of Ca2+ activity, we have proposed the method of vital identification of neurons containing CP-AMPARs. Using this method we demonstrate that approximately 80% CP-AMPARs-containing neurons in rat hippocampal cell cultures are GABAergic. As with most GABAergic neurons, GABAergic neurons containing CP-AMPARs demonstrate weaker GABA(A)R-mediated innervation compared to glutamatergic neurons. This peculiarity together with the presence of CP-AMPARs may contribute to vulnerability of these neurons to excitotoxicity. Image content Microphotographs of neurons in rat hippocampal neuron-glial culture stained with antibodies against GABA (red) and a marker of a GABAergic synapse, vesicular GABA transporter (green puncta). The panel shows the distribution of GABAergic synapses on two glutamatergic neurons (left image) and GABAergic neuron with (right image) and without CP-AMPARs (middle image). Read the full article ‘A novel approach for vital visualization and studying of neurons containing Ca2+-permeable AMPA receptors’ by S. G. Gaidin, S. A. Maiorov, D. P. Laryushkin, V. P. Zinchenko and A. M. Kosenkov, (J. Neurochem. 2023, vol.164 (5), pp. 583–587) on doi:10.1111/jnc.15729

Precise analysis of thyroxine enantiomers in pharmaceutical formulation by mobility difference based on cyclodextrin

Identification and determination of chiral pharmaceutical residues is still a challenging analytical puzzle. In this work, a simple, rapid, and effective method for chiral D/L-tetraiodothyronine (T4) separation and quantitative was developed based on host–guest recognition using ion mobility spectrometry-mass spectrometry (IMS-MS). The D/L-T4 enantiomers were mobility separated by their diastereomeric complexes through mixing with cyclodextrin (CD) and metal ions. D/L-T4 was first separated by complexing with host molecule (α-, β-, γ-CD), observing weak peak-to-peak resolution (Rp-p) by the formed binary complex [CD + D/L-T4-H]+, and the Rp-p decreased with the CD size increasing. However, the separation effect of D/L-T4 was much improved with the addition of divalent metal ions (G2+) by the formed ternary complex [CD + D/L-T4 + G]2+. In comparison, α-CD related complexes can possess the best separation effect for D/L-T4 in most cases. Considering the high selectivity, non-toxic, and chemically stable of β-CD, [β-CD + D/L-T4 + Ca]2+ was selected for D/L-T4 analysis (RP-P = 0.764). Whereafter, chemical theoretical conformations for [β-CD + D/L-T4 + H]+ and [β-CD + D/L-T4 + Ca]2+ were optimized, discovering similar micro-interaction modes between [β-CD + D-T4 + H]+ and [β-CD + L-T4 + H]+; while with the addition of Ca2+, significantly different interaction modes were observed between [β-CD + D-T4 + Ca]2+ and [β-CD + L-T4 + Ca]2+. And theoretical collision cross section (CCS) trends for the complexes were consistent with that of the experimental results. Additionally, calibration curves were linear within 1.00 to 104 ng mL−1 with coefficient (R2 > 0.99), gaining the limit of detection (LODs) calculation of 0.11 ng mL−1, and the detection range between D-T4 and L-T4 of 45.6:1 to 1:59.8. Finally, the method was applied for D/L-T4 detection in Levothyroxine tablets, the detection content has good consistency on drug labeling. Because the proposed method exhibited good analytical performance in terms of speed, selectivity, sensitivity, and reproducibility of the measurements, that can be a promising strategy for effective D/L-T4 detection in pharmaceutical industries or other practical samples.

The Influence of Small Additions of Alloying Elements on the Hot Ductility of AHSS Steels: A Critical Review Part 2

In this paper, the influence of small additions of Cr, Mo, Cu, Ni, B, Ca, Zr, and Ce on the hot ductility of advanced high-strength steels (AHSS) has been reviewed. Most of these small additions have a positive effect in improving hot ductility on straightening during continuous casting operations and should be considered when problems with cracking in continuous casting are encountered. In many of these cases, the reason for these generally small but important improvements in hot ductility is not known with certainty, but the segregation of these elements to the austenite grain boundaries, strengthening the bonding, is often suggested.

The Effect of Decreased Ca++/Mg++ ATPase Activity on Lactobacillus delbrueckii subsp. bulgaricus sp1.1 Survival during Spray Drying.

Compared with the commonly used technique of freeze-drying, spray drying has lower energy costs. However, spray drying also has a fatal disadvantage: a lower survival rate. In this study, the survival of bacteria in a spray-drying tower decreased as the water content was reduced. The water content of 21.10% was the critical point for spray drying Lactobacillus delbrueckii subsp. bulgaricus (L. bulgaricus) sp1.1 based on sampling in the tower. Based on the relationship between the moisture content of spray drying and the survival rate, the water content of 21.10% was also the critical point for the change in the survival rate during spray drying. Proteomic analysis was used to investigate the reasons for L. bulgaricus sp1.1 inactivation during and after spray drying. Gene Ontology (GO) enrichment revealed that differentially expressed proteins were mainly associated with the cell membrane and transport. In particular, proteins related to metal ion transport included those involved in the transport of potassium, calcium and magnesium ions. The protein-protein interaction (PPI) network revealed that Ca++/Mg++ adenosine triphosphatase (ATPase) may be a key protein. Ca++/Mg++ ATPase activity decreased substantially during spray drying (p < 0.05). Supplementation with Ca++ and Mg++ significantly increased the expression of ATPase-related genes and enzyme activity (p < 0.05). The Ca++/Mg++ ATPase activity of L. bulgaricus sp1.1 was enhanced by increasing the intracellular Ca++ or Mg++ concentration, thus increasing the survival of spray-dried LAB. Bacterial survival rates were increased to 43.06% with the addition of Ca++ and to 42.64% with the addition of Mg++, respectively. Ca++/Mg++ ATPase may be the key to the damage observed in spray-dried bacteria. Furthermore, the addition of Ca++ or Mg++ also reduced bacterial injury during spray drying by enhancing the activity of Ca++/Mg++ ATPase.

The enhanced Zn and Ca co-segregation and mechanical properties of Mg–Zn–Ce alloy with micro Ca addition

The micro addition of Ca is demonstrated to noticeably increase the strength and ductility of Mg–Zn–Ce alloy, which is closely correlated with the enhanced alloying segregation at grain boundary. Addition of Ca is found to yield the enhanced Zn segregation and co-segregation of Zn, Ce, and Ca. The mechanism behind is that Ca decreases the segregation energy while promoting the diffusion process of Zn, ultimately accelerating the thermodynamic and kinetic process of segregation. The enhanced alloying segregation induced by Ca effectively stabilizes grain boundary, which contributes to the refined grain size, retardant mobility of dislocation and ultimately improved strength. Furthermore, the intergranular fracture energy can be noticeably increased by Ca owing to the promoted alloying element segregation at grain boundary, which contributes to the improved grain boundary cohesion and ductility. The controllable segregation at grain boundary via alloying is intended to contribute to the development of advanced magnesium alloys.

Calcium and Sodium-mediated Dynamic Assembly of Intermediate Filament-like Protein FilP.

Cytoskeletal elements play key roles in cell morphology, cell division, cell mobility, and DNA partitioning in all domains of life. The IF-like protein FilP was discovered in Streptomyces coelicolor, and it was found to perform a structurally important cytoskeletal role by providing direct mechanical support for the cells. This work investigated the factors influencing FilP polymerization under a variety of conditions. DLS technique was applied to real-time monitor the in vitro assembly process of Streptomyces coelicolor FilP. The presence of small amounts of divalent cations, such as CaCl2 or MgCl2, enhanced the polymerization of FilP, while higher amounts suppressed its polymerization. Moreover, high concentrations of NaCl, KCl, NH4Cl, and KNO3 both suppressed the polymerization of FilP. EDTA was found to have a very prohibitive effect on FilP polymerization, and even the following addition of Ca2+ could not initiate the assembly of FilP. FilP polymerized under a range of pHs ranging from pH 6 to pH 8, while the polymerization degree was sensitive to pH. FilP formed network-like, striated filaments at neutral pH, while the filaments became more disordered or loosely packed at pH 8 and pH 6, respectively. FilP assembly is calcium-mediated. Ca2+ is not only required for FilP polymerization, but also required for FilP to maintain the higher-order polymer structure. The accelerative effect of Ca2+ and the suppressive effect of Na+ persisted under a wide range of conditions, suggesting that FilP might use calcium and sodium ions as a general mechanism to mediate its polymerization process.

Effects of Ca and Nd addition on plastic instability in extruded Mg-Mn alloy deformed under various conditions

Effects of Ca and Nd addition on plastic instability in extruded Mg-Mn alloy deformed under various conditions

Calcium-dependent shifts between phospholamban (PLB) monomers and homo-pentamers reveal the interactions between PLB and SERCA in native cardiac membranes.

Phospholamban monomer (PLB1) binds to the cardiac calcium pump (SERCA2a) and inhibits the enzyme. PLB homopentamers (PLB5) are inactive species, but stable in SDS that correlate well to that in the native membranes. In contrast, SDS separates PLB1 from SERCA2a. Using this feature, we developed assays to probe the constant exchanging PLB1 with SERCA2a, and with PLB5, in native cardiac sarcoplasmic reticulum (SR) membrane vesicles. Dog cardiac SR was pre-incubated at 37°C in 1mM EGTA, allowing PLB1 binding to SERCA2a. Then, 8 µg samples were incubated for 1 min with control buffer, 1mM Ca (free [Ca] = 16.4 µM), 1 mM Ca first and then 5 mM EGTA (free [Ca] = 0.06 µM), or 10µM SERCA2a inhibitor thapsigargin. These reactions were stopped by 1% SDS before SDS-PAGE and immunoblotting to measure PLB5/PLB1 ratios. Addition of Ca significantly increased PLB5/PLB1 to 2.91 ± 0.38 from 1.22 ± 0.08 in the control, Ca-free condition, suggesting that Ca activation of the pump dissociates the whole PLB monomer from inhibitory site on SERCA2a in cardiac membranes. Furthermore, subsequent addition of EGTA reversed Ca-induced increased in PLB5/PLB1 back to 1.38 ± 0.15. Meanwhile, thapsigargin virtually eliminated PLB1 binding to SERCA2a, increasing PLB5/PLB1 to 3.13 ± 0.40. In control experiments, none of these factors affected PLB5/PLB1 of WT-PLB expressed alone in insect cells. Therefore, the detected changes in PLB5/PLB1 must occur in the native SR membranes, reflecting fully reversible processes of Ca-dependent PLB1 association and dissociation from the inhibitory site on SERCA2a, followed by disassembling and assemblage into PLB5, respectively. Such assays will allow further studies to determine the effect of allosteric factors and proteins phosphorylation on the interactions between PLB and SERCA2a directly in native cardiac SR membranes.

Tau liquid-liquid phase separation is modulated by the Ca2+ -switched chaperone activity of the S100B protein.

Aggregation of the microtubule-associated protein tau is implicated in several neurodegenerative tauopathies including Alzheimer's disease (AD). Recent studies evidenced tau liquid-liquid phase separation (LLPS) into droplets as an early event in tau pathogenesis with the potential to enhance aggregation. Tauopathies like AD are accompanied by sustained neuroinflammation and the release of alarmins at early stages of inflammatory responses encompass protective functions. The Ca2+ -binding S100B protein is an alarmin augmented in AD that was recently implicated as a proteostasis regulator acting as a chaperone-type protein, inhibiting aggregation and toxicity through interactions of amyloidogenic clients with a regulatory surface exposed upon Ca2+ -binding. Here we expand the regulatory functions of S100B over protein condensation phenomena by reporting its Ca2+ -dependent activity as a modulator of tau LLPS induced by crowding agents (PEG) and metal ions (Zn2+ ). We observe that apo S100B has a negligible effect on PEG-induced tau demixing but that Ca2+ -bound S100B prevents demixing, resulting in a shift of the phase diagram boundary to higher crowding concentrations. Also, while incubation with apo S100B does not compromise tau LLPS, addition of Ca2+ results in a sharp decrease in turbidity, indicating that interactions with S100B-Ca2+ promote transition of tau to the mixed phase. Further, electrophoretic analysis and FLIM-FRET studies revealed that S100B incorporates into tau liquid droplets, suggesting an important stabilizing and chaperoning role contributing to minimize toxic tau aggregates. Resorting to Alexa488-labeled tau we observed that S100B-Ca2+ reduces the formation of tau fluorescent droplets, without compromising liquid-like behavior and droplet fusion events. The Zn2+ -binding properties of S100B also contribute to regulate Zn2+ -promoted tau LLPS as droplets are decreased by Zn2+ buffering by S100B, in addition to the Ca2+ -triggered interactions with tau. Altogether this work uncovers the versatility of S100B as a proteostasis regulator acting on protein condensation phenomena of relevance across the neurodegeneration continuum.

In vitro degradation and corrosion evaluations of plasma electrolytic oxidized Mg–Zn–Ca–Si alloys for biomedical applications

Biodegradable calcium phosphate (CaP) ceramic coatings were prepared on self-designed Mg-2.0Zn-0.6Ca-xSi alloys by plasma electrolytic oxidation (PEO). The effect of calcium (Ca) and silicon (Si) on alloy microstructure and coating formation and biomineralization mechanisms were discussed. The in vitro bioactivity and degradability of CaP coatings were evaluated by immersion tests in simulated body fluid (SBF) solutions and trishydroxymethyl-aminomethane hydrochloric acid (Tris-HCl) buffer, respectively. The microstructure and chemical composition of the coatings, depositions and corrosion products were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) and fourier transform infrared spectrometer (FT-IR). The electrochemical corrosion behavior of alloys and coatings was investigated using the electrochemical workstation. Results showed that the shape, quantity, size and distribution of second phases can be changed by the simultaneously addition of Ca and Si in Mg–Zn–Ca–Si alloys. The Si content in Mg-2.0Zn-0.6Ca-xSi alloy should not be higher than 0.8 wt%. The microstructure of Mg-2.0Zn-0.6Ca-xSi alloys can influence the formation and growth of PEO coating by altering the spark discharge characteristics. The plasma electrolytic oxidized Mg-2.0Zn-0.6Ca-0.8Si has potential to be served as biodegradable bone implant and cardiovascular stent.