Low Ionic Strength Research Articles

Effect of cation species on pressure-driven electrokinetic energy conversion in charged conical nanochannels

Electrokinetic energy conversion (EEC) offers a promising avenue for transforming elusive natural energy into electric power, showing a wide application spectrum. Unlike prevalent studies that chiefly utilize symmetrical electrolyte solution (e.g., KCl) and uniformly structured negatively charged nanochannels for EEC, this paper delves into a thorough examination of EEC characteristics—streaming current, streaming potential, and output power—in both positively and negatively charged conical nanochannels with symmetrical and asymmetric (CaCl2 and LaCl3) electrolytes solutions. Operating under the assumption that the electrolyte solutions (KCl, CaCl2, and LaCl3) possess equivalent ionic strength and, thereby, a common Debye length, our findings reveal a significant dependency of EEC characteristics and their regulation parameters on the electrolyte type, nanochannel charge polarity, and ionic strength. As the ionic strength increases, both the streaming current and output power initially rise to a peak before subsequently declining, with the ionic strength at the peak being influenced by the cation valence: lower valence leads to lower ionic strength. In asymmetric electrolyte scenarios, optimal EEC characteristic is observed in positively charged conical nanochannels under a reverse pressure difference, attributed to the ion-selective and ionic concentration distribution in the charged conical nanochannels. Moreover, the complex behaviors of the regulation parameters of EEC characteristics are unveiled. Notably, a tri-valent electrolyte's regulation parameters exceed those of a bi-valent electrolyte, indicating that ionic valence asymmetry enhances the regulation effects on EEC in conical nanochannels.

Does the ionic distribution in the electrical double layer modify second harmonic scattering?

Surface-specific nonlinear optical techniques are ideally suited to investigate the complex structure of aqueous interfaces. For colloidal particles dispersed in aqueous solutions, interfacial properties can be retrieved with angle-resolved second harmonic scattering (AR-SHS). The mathematical framework of AR-SHS does not require a priori knowledge on the electrostatic distribution in the first few nanometers close to the interface, therefore allowing us to formulate a molecular-level description of the electrical double layer (EDL) based on the experimental data. However, farther away from the interface, an analytical form of the electrostatic potential decay is necessary to account for the distance dependence of the surface electrostatic field propagating into the solution. This requirement is especially important at low ionic strengths, where the electrostatic field is not efficiently screened by counterions. Here, we examine to what extent the analytical form of the electrostatic potential decay impacts the AR-SHS data analysis. We analyze the effect of different functions on the scattering form factors, on the integrated AR-SHS signal intensity, and on the surface parameters extracted from fitting the AR-SHS data. We find that the trends of the surface parameters remain similar regardless of the chosen function, demonstrating the robustness of our approach to establish a molecular-level picture of the EDL. At ionic strengths <10-4M for 100-nm diameter particles, a functional form that physically represents counterions packed more densely in the vicinity of the surface than in the case of the Poisson-Boltzmann distribution has the largest impact, resulting in an overestimation of the obtained surface potential.

Taylor Dispersion‐Induced Phase Separation for the Efficient Characterisation of Protein Condensate Formation

AbstractBiomolecular condensates have emerged as important structures in cellular function and disease, and are thought to form through liquid‐liquid phase separation (LLPS). Thorough and efficient in vitro experiments are therefore needed to elucidate the driving forces of protein LLPS and the possibility to modulate it with drugs. Here we present Taylor dispersion‐induced phase separation (TDIPS), a method to robustly measure condensation phenomena using a commercially available microfluidic platform. It uses only nanoliters of sample, does not require extrinsic fluorescent labels, and is straightforward to implement. We demonstrate TDIPS by screening the phase behaviour of two proteins that form biomolecular condensates in vivo, PGL‐3 and Ddx4. Uniquely accessible to this method, we find an unexpected re‐entrant behaviour at very low ionic strength, where LLPS is inhibited for both proteins. TDIPS can also probe the reversibility of assemblies, which was shown for both α‐synuclein and for lysozyme, relevant for health and biotechnology, respectively. Finally, we highlight how effective inhibition concentrations and partitioning of LLPS‐modifying compounds can be screened highly efficiently.

Taylor Dispersion-Induced Phase Separation for the Efficient Characterisation of Protein Condensate Formation.

Biomolecular condensates have emerged as important structures in cellular function and disease, and are thought to form through liquid-liquid phase separation (LLPS). Thorough and efficient in vitro experiments are therefore needed to elucidate the driving forces of protein LLPS and the possibility to modulate it with drugs. Here we present Taylor dispersion-induced phase separation (TDIPS), a method to robustly measure condensation phenomena using a commercially available microfluidic platform. It uses only nanoliters of sample, does not require extrinsic fluorescent labels, and is straightforward to implement. We demonstrate TDIPS by screening the phase behaviour of two proteins that form biomolecular condensates in vivo, PGL-3 and Ddx4. Uniquely accessible to this method, we find an unexpected re-entrant behaviour at very low ionic strength, where LLPS is inhibited for both proteins. TDIPS can also probe the reversibility of assemblies, which was shown for both α-synuclein and for lysozyme, relevant for health and biotechnology, respectively. Finally, we highlight how effective inhibition concentrations and partitioning of LLPS-modifying compounds can be screened highly efficiently.

Exploring the impact of solvent additives on dielectric properties in polymer photovoltaics: A deconvolution and in-depth study of electrical modulus, complex conductivity, and impedance responses

Impedance and dielectric spectroscopy is a well-known technique for characterizing interfaces, especially donor/receiver interfaces in bulk heterojunction (BHJ) solar cells. This technique was employed to investigate the interface of poly (4,8-bis-alkyloxybenzo(1,2-b:4,5-b0) dithio-phene-2,6-diyl-alt- (alkyl thieno (3,4-b) thiophene-2-carboxylate)-2,6-diyl) (PBDTTT-C): PC70BM in bulk heterojunction with DIO as additive. For this reason, a simulation was carried out to generate the complex impedance, modulus, and complex conductivity data based on the electrical parameters extracted from the equivalent circuit. Therefore, a new approach based on the coupling of complex functions such as impedance, modulus, and conductivity has been proposed. In addition, an extrapolation and deconvolution approaches are used to highlight the relaxation processes, the BHJ layer process, the two electrical contacts of the interfaces between PEDOT: PSS/PBDTTT-C: PC70BM and PBDTTT-C: PC70BM/Ca process, and the electrode polarization process. In the next step, the remove the low-frequency process enhances the visibility of other processes, particularly observable in the evolution of the electrical modulus and the conduction parameters associated with each process. In the complex functions, there was a good correlation between all parameters derived from both processes. The characteristics of the conduction processes, such as conductivity values at low and high frequencies and ionic strength were then extracted. All these parameters were evaluated and discussed as a function of the thickness of the active layer. Finally, we demonstrate that the electrical modulus and complex conductivity can be perfect tools to characterize the donor/acceptor interfaces.

Tail length and E525K dilated cardiomyopathy mutant alter human β-cardiac myosin super-relaxed state.

Dilated cardiomyopathy (DCM) is a condition characterized by impaired cardiac function, due to myocardial hypo-contractility, and is associated with point mutations in β-cardiac myosin, the molecular motor that powers cardiac contraction. Myocardial function can be modulated through sequestration of myosin motors into an auto-inhibited "super-relaxed" state (SRX), which may be further stabilized by a structural state known as the "interacting heads motif" (IHM). Here, we sought to determine whether hypo-contractility of DCM myocardium results from reduced function of individual myosin molecules or from decreased myosin availability to interact with actin due to increased IHM/SRX stabilization. We used an established DCM myosin mutation, E525K, and characterized the biochemical and mechanical activity of wild-type and mutant human β-cardiac myosin constructs that differed in the length of their coiled-coil tail, which dictates their ability to form the IHM/SRX state. We found that short-tailed myosin constructs exhibited low IHM/SRX content, elevated actin-activated ATPase activity, and fast velocities in unloaded motility assays. Conversely, longer-tailed constructs exhibited higher IHM/SRX content and reduced actomyosin ATPase and velocity. Our modeling suggests that reduced velocities may be attributed to IHM/SRX-dependent sequestration of myosin heads. Interestingly, longer-tailed E525K mutants showed no apparent impact on velocity or actomyosin ATPase at low ionic strength but stabilized IHM/SRX state at higher ionic strength. Therefore, the hypo-contractility observed in DCM may be attributable to reduced myosin head availability caused by enhanced IHM/SRX stability in E525K mutants.

Engineering of chimeric enzymes with expanded tolerance to ionic strength.

Antimicrobial resistance poses a significant global threat, reaching dangerously high levels as reported by the World Health Organization. The emergence and rapid spread of new resistance mechanisms, coupled with the absence of effective treatments in recent decades, have led to thousands of deaths annually from infections caused by drug-resistant microorganisms. Consequently, there is an urgent need for the development of new compounds capable of combating antibiotic-resistant bacteria. A promising class of molecules exhibiting potent bactericidal effects is peptidoglycan hydrolases. Previously, we cloned and characterized the biochemical properties of the M23 catalytic domain of the EnpA (EnpACD) protein from Enterococcus faecalis. Unlike other enzymes within the M23 family, EnpACD demonstrates broad specificity. However, its activity is constrained under low ionic strength conditions. In this study, we present the engineering of three chimeric enzymes comprising EnpACD fused with three distinct SH3b cell wall-binding domains. These chimeras exhibit enhanced tolerance to environmental conditions and sustained activity in bovine and human serum. Furthermore, our findings demonstrate that the addition of SH3b domains influences the activity of the chimeric enzymes, thereby expanding their potential applications in combating antimicrobial resistance.IMPORTANCEThese studies demonstrate that the addition of the SH3b-binding domain to the EnpACD results in generation of chimeras with a broader tolerance to ionic strength and pH values, enabling them to remain active over a wider range of conditions. Such approach offers a relatively straightforward method for obtaining antibacterial enzymes with tailored properties and emphasizes the potential for proteins' engineering with enhanced functionality, contributing to the ongoing efforts to address antimicrobial resistance effectively.

Polymer Coatings Affect Transport and Remobilization of Colloidal Activated Carbon in Saturated Sand Columns: Implications for In Situ Groundwater Remediation.

Colloidal activated carbon (CAC) is an emerging technology for the in situ remediation of groundwater impacted by per- and polyfluoroalkyl substances (PFAS). In assessing the long-term effectiveness of a CAC barrier, it is crucial to evaluate the potential of emplaced CAC particles to be remobilized and migrate away from the sorptive barrier. We examine the effect of two polymer stabilizers, carboxymethyl cellulose (CMC) and polydiallyldimethylammonium chloride (PolyDM), on CAC deposition and remobilization in saturated sand columns. CMC-modified CAC showed high mobility in a wide ionic strength (IS) range from 0.1 to 100 mM, which is favorable for CAC delivery at a sufficient scale. Interestingly, the mobility of PolyDM-modified CAC was high at low IS (0.1 mM) but greatly reduced at high IS (100 mM). Notably, significant remobilization (release) of deposited CMC-CAC particles occurred upon the introduction of solution with low IS following deposition at high IS. In contrast, PolyDM-CAC did not undergo any remobilization following deposition due to its favorable interactions with the quartz sand. We further elucidated the CAC deposition and remobilization behaviors by analyzing colloid-collector interactions through the application of Derjaguin-Landau-Verwey-Overbeek theory, and the inclusion of a discrete representation of charge heterogeneity on the quartz sand surface. The classical colloid filtration theory was also employed to estimate the travel distance of CAC in saturated columns. Our results underscore the roles of polymer coatings and solution chemistry in CAC transport, providing valuable guidelines for the design of in situ CAC remediation with maximized delivery efficiency and barrier longevity.

Leaching behaviour of 226Ra from uranium tailings and adsorption behaviour in geotechnical medias

The leaching process of uranium tailings is a typical water-rock interaction. The release of 226Ra from uranium tailings depends on the nuclides outside the intrinsic properties of uranium tailings on the one hand, and is influenced by the water medium on the other. In this paper, a uranium tailings repository in southern China was used as a research object, and uranium tailings at different depths were collected by drilling samples and mixed to analyze the 226Ra occurrence states. Static dissolution leaching experiments of 226Ra under different pH conditions, solid-liquid ratio conditions, and ionic strength conditions were carried out, and the adsorption and desorption behaviours of 226Ra in five representative stratigraphic media were investigated. The results show that 226Ra has a strong adsorption capacity in representative strata, with adsorption distribution coefficient Kd values ranging from 1.07E+02 to 1.29E+03 (mL/g) and desorption distribution coefficients ranging from 4.97E+02 to 2.71E+03 (mL/g), but the adsorption is reversible. The 226Ra in uranium tailings exists mainly in the residual and water-soluble states, and the release of 226Ra from uranium tailings under different conditions is mainly from the water-soluble and exchangeable state fractions. Low pH conditions, low solid-liquid ratio conditions and high ionic strength conditions are favourable to the release of 226Ra from uranium tailings, so the release of 226Ra from uranium tailings can be reduced by means of adjusting the pH in the tailings and setting up a water barrier. The results of this research have important guiding significance for the management of existing uranium tailings ponds and the control of 226Ra migration in groundwater, which is conducive to guaranteeing the long-term safety, stability and sustainability of uranium mining sites.

Synergistic effect of Ti3C2Tx MXene/PAN nanofiber and LLZTO particles on high-performance PEO-based solid electrolyte for lithium metal battery

Solid polymer electrolytes (SPEs) have been considered the most promising separators for all-solid-state lithium metal batteries (ASSLMBs) due to their ease of processing and low cost. However, the practical applications of SPEs in ASSLMBs are limited by their low ionic conductivities and mechanical strength. Herein, we developed a three-dimensional (3D) interconnected MXene (Ti3C2Tx) network and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) particles synergistically reinforced polyethylene oxide (PEO)-based SPE, where the association of Li+ with ether-oxygen in PEO could be significantly weakened through the Lewis acid-base interactions between the electron-absorbing group (Ti–F, −O–) of Ti3C2Tx and Li+. Besides, the TFSI− in lithium salts could be immobilized by hydrogen bonds from the Ti–OH of Ti3C2Tx. The 3D interconnected Ti3C2Tx network not only alleviated the agglomeration of inorganic fillers (LLZTO), but also improved the mechanical strength of composite solid electrolyte (CSE). Consequently, the assembled Li||CSE||Li symmetric battery showed excellent cycling stability at 35 ℃ (stable cycling over 3000 h at 0.1 mA cm−2, 0.1 mAh cm−2) and −2 ℃ (stable cycling over 2500 h at 0.05 mA cm−2, 0.05 mAh cm−2). Impressively, the LiFePO4||CSE||Li battery showed a high discharge capacity of 145.3 mAh/g at 0.3 C after 300 cycles at 35 ℃. This rational structural design provided a new strategy for the preparation of high-performance solid-state electrolytes for lithium metal batteries.

Molecular Dynamics Insights into the Aggregation Behavior of N-Terminal β-Lactoglobulin Peptides.

β-lactoglobulin (BLG) forms amyloid-like aggregates at high temperatures, low pH, and low ionic strengths. At a pH below 2, BLG undergoes hydrolysis into peptides, with N-terminal peptides 1-33 and 1-52 being prone to fibrillization, forming amyloid-like fibrils. Due to their good mechanical properties, BLG amyloids demonstrate great potential for diverse applications, including biosensors, nanocomposites, and catalysts. Consequently, further studies are essential to comprehensively understand the factors governing the formation of BLG amyloid-like morphologies. In this study, all-atom molecular dynamics simulations were employed to explore the aggregation of N-terminal 1-33 and 1-52 BLG peptides under conditions of pH 2 and at 10 mM NaCl concentration. The simulations revealed that the peptides spontaneously assembled into aggregates of varying sizes. The aggregation process was enabled by the low charge of peptides and the presence of hydrophobic residues within them. As the peptides associated into aggregates, there was a concurrent increase in β-sheet structures and the establishment of hydrogen bonds, enhancing the stability of the aggregates. Notably, on average, 1-33 peptides formed larger aggregates compared to their 1-52 counterparts, while the latter exhibited a slightly higher content of β-sheets and higher cluster orderliness. The applied approach facilitated insights into the early stages of amyloid-like aggregation and molecular-level insight into the formation of β-sheets, which serve as nucleation points for further fibril growth.

Transport and retention of positively charged zinc oxide nanoparticles in saturated porous media: Effects of metal oxides and clays

The effects of metal oxides and clays on the transport of zinc oxide nanoparticles (ZnO-NPs) in saturated porous media were investigated under different ionic strength (IS) conditions. We studied the transport and retention behavior of ZnO-NPs for different types of porous media (untreated, acid treated, and acid–salt treated sand). The selected untreated sand was used as a representative sand, coated with both metal oxide and clay. The acid treated and acid–salt-treated sands were used and compared to investigate the effects of clays on the surface of the sand. In addition, the effects of clay particles in bulk solutions on the mobility and retention of ZnO-NPs were observed using bentonite as a representative clay particle. We found that the increased mobility of positively charged ZnO-NPs can be attributed to increasing charge heterogeneity of silica sand with metal oxides (mainly, iron oxide) and clays in untreated sand. No breakthrough of ZnO-NP was observed for acid-treated (presence of clays and absence of metal oxides) and acid–salt-treated sand (absence of both metal oxide and clays). Most of the injected ZnO-NPs were deposited on the surface of the sand near the column inlet. The transport of bentonite-facilitated ZnO-NPs was improved at the lowest IS (0.1 mM) (∼20%), whereas there was no difference in the mobility of ZnO-NPs at high IS solutions (1 mM and 10 mM). In particular, the breakthrough amount improved with increasing bentonite concentration. Classical Derjaguin–Landau–Verwey–Overbeek interactions help explain observed interactions between ZnO-NPs and sand as well as bentonite and sand.

Plasmid size determines adsorption to clay and breakthrough in a saturated sand column

Horizontal gene transfer (HGT) is a major factor in the spread of antibiotic resistant genes (ARG). Transformation, one mode of HGT, involves the acquisition and expression of extracellular DNA (eDNA). eDNA in soils is degraded rapidly by extracellular nucleases. However, if bound to a clay particle, eDNA can persist for long periods of time without losing its transformation ability. To better understand the mechanism of eDNA persistence in soil, this experiment assessed the effects of 1) clay mineralogy, 2) mixed salt solution, 3) plasmid size on DNA adsorption to clay and 4) breakthrough behavior of three differently sized plasmids in an environmentally relevant solution. Batch test methods were used to determine adsorption trends of three differently sized DNA plasmids, pUC19, pBR322, and pTYB21, to several pure clay minerals, goethite (α-FeOOH), illite, and kaolinite, and one environmental soil sample. Results show not all sorbents have equal adsorption capacity based on surface area with adsorption capacities decreasing from goethite > illite = kaolinite > bulk soil, and low ionic strength solutions will likely not significantly alter sorption trends. Additionally, plasmid DNA size (i.e., length) was shown to be a significant predictor of adsorption efficiency and that size affects DNA breakthrough, with breakthroughs occurring later with larger plasmids. Given that DNA persistence is linked to its adsorption to soil constituents and breakthrough, eDNA size is likely an important contributor to the spread of ARG within natural microbial communities.

Stability enhancement of pickering emulsions based on κ-carrageenan microgel: Synergistic effect of l-lysine and potassium ions at low ionic strength

The study utilized the synergistic effect of l-lysine and K+ to improve the stability of Pickering emulsions based on κ-carrageenan microgels. The gel strength of κ-carrageenan gels, the zeta potential and particle size revealed that the microgel particles prepared with l-lysine and K+ had the potential to be Pickering particles. l-lysine formed electrostatic interactions and hydrogen bonds with κ-carrageenan. Structural modifications of microgel particles by l-lysine (0.05%–0.10%) and low K+ strength (≤40 mmol/L) promoted the formation of a dense interface layer at the oil-water droplet surface to prevent the accumulation of oil droplets and further significantly enhance the appearance and centrifugal stability of Pickering emulsions. The microstructure and rheological analysis showed that K+ at low ionic strength, in cooperation with l-lysine, formed a more tightly structured layer between the microgel particles wrapped on the surface of oil droplets, thereby enhancing the stability of emulsions. In conclusion, these Pickering emulsions with prolonged stability are expected to be suitable healthy animal fat substitutes for use in food applications.

How hydrophobicity, side chains, and salt affect the dimensions of disordered proteins.

Despite the generally accepted role of the hydrophobic effect as the driving force for folding, many intrinsically disordered proteins (IDPs), including those with hydrophobic content typical of foldable proteins, behave nearly as self-avoiding random walks (SARWs) under physiological conditions. Here, we tested how temperature and ionic conditions influence the dimensions of the N-terminal domain of pertactin (PNt), an IDP with an amino acid composition typical of folded proteins. While PNt contracts somewhat with temperature, it nevertheless remains expanded over 10-58°C, with a Flory exponent, ν, >0.50. Both low and high ionic strength also produce contraction in PNt, but this contraction is mitigated by reducing charge segregation. With 46% glycine and low hydrophobicity, the reduced form of snow flea anti-freeze protein (red-sfAFP) is unaffected by temperature and ionic strength and persists as a near-SARW, ν ~ 0.54, arguing that the thermal contraction of PNt is due to stronger interactions between hydrophobic side chains. Additionally, red-sfAFP is a proxy for the polypeptide backbone, which has been thought to collapse in water. Increasing the glycine segregation in red-sfAFP had minimal effect on ν. Water remained a good solvent even with 21 consecutive glycine residues (ν > 0.5), and red-sfAFP variants lacked stable backbone hydrogen bonds according to hydrogen exchange. Similarly, changing glycine segregation has little impact on ν in other glycine-rich proteins. These findings underscore the generality that many disordered states can be expanded and unstructured, and that the hydrophobic effect alone is insufficient to drive significant chain collapse for typical protein sequences.

Variable-Angle Surface Spectroscopy Reveals the Water Structure in the Stern Layer at Charged Aqueous Interfaces.

At charged aqueous interfaces, the second-order nonlinear optical response originates from water molecules within the diffuse part of the electrical double layer, which are ordered by the surface field and from water that additionally experiences chemical and physical interactions with the surface in the Stern layer. These two environments can either reinforce or diminish the overall signal and can be disentangled by varying the coherence length of their interaction with external laser fields. Here, we demonstrate a method in which the angle of incidence is varied to afford a significant change in the coherence length. When this technique was applied to the silica-water interface, it was observed that water molecules in the Stern and diffuse layers direct their hydrogen atoms toward the mineral surface at a low ionic strength and neutral pH. A decrease in the signal with increasing ionic strength is attributed to hydrated cation adsorption that competes with free water for deprotonated silanol sites.

When you think you should transfuse…don't!

A 48-year-old female presented to the emergency department with severe fatigue. Admission laboratory test results were hemoglobin 6.6 g/dL, platelet count 287,000/μL, and white blood cell count 25,200/μL. Lactate dehydrogenase was elevated at 898 U/L, haptoglobin was markedly decreased (< 31 mg/dL), indirect bilirubin was elevated (5.3 mg/dL), and the absolute reticulocyte count was low at 0.0050/μL. A sample was sent to the immunohematology reference laboratory. The direct antiglobulin test immunoglobulin G was negative; C3 was 1+. All cells were reactive at immediate spin phase, indirect antiglobulin testing (IAT) with polyethylene glycol, with low ionic strength saline, neat, prewarm, and in the solid phase. All cells were nonreactive at IAT-ficin. Additional testing included a cold antibody titer that was 1:4096 and thermal amplitude studies demonstrating reactivity of 2+ at 37°C. These results were consistent with a clinically significant anti-Pr and cold agglutinin disease (CAD). Although rituximab is effective in autoimmune hemolytic anemia, this may take weeks. The patient was treated with pegcetacoplan, a pegylated peptide that targets C3 inhibiting hemolysis. The patient was discharged on day 29 with a hemoglobin of 8 g/dL. This is a report of one of the first patients successfully treated with pegcetacoplan for CAD.

Protein analysis using capillary electrophoresis coupled to mass spectrometry through vibrating sharp-edge spray ionization.

Capillary electrophoresis (CE) interfaced to mass spectrometry (MS) with electrospray ionization typically incorporates acidic additives or organic solvents to assist in ionization. Vibrating sharp-edge spray ionization (VSSI) is a voltage-free method to interface CE and MS that does not require these additives, making it appealing for protein analyses. CE-VSSI nanoflow sheath separations are performed with low ionic strength aqueous solutions in the sheath to reduce suppression. Serine is also included in the sheath to reduce analyte adduction. Proteins are detected in the 2.5-10µM range, corresponding to an injected mass range of 0.1-1.2ng. The anionic proteins β-lactoglobulin and transferrin are resolved using an unmodified fused silica capillary because they do not exhibit nonspecific surface adsorption. Conversely, separations of cationic proteins cytochrome c, ribonuclease A, and α-chymotrypsinogen A in an unmodified capillary require acidic background electrolytes to overcome adsorption. Alternatively, a semipermanent coating comprised self-assembled lipids overcomes surface adsorption at a neutral pH. Separations with zwitterionic and hybrid cationic coatings are complete within 15 or 6min, respectively. The dimeric form of triosephosphate isomerase was observed at a 60µM, corresponding to a mass of 19ng, by dropping the temperature of the MS inlet.

Equilibrium Fractionation of Stable Strontium Isotopes During Adsorption to Mn Oxides

AbstractUnderstanding the stable strontium isotope fractionation between seawater and ferromanganese crusts/nodules is crucial for reconstructing seawater Sr isotopic history. This study explores stable Sr isotope fractionation during adsorption to manganese oxides, as preliminary experiments indicated their higher Sr adsorption capacity compared to iron oxides. We observed that equilibrium in concentration and isotopic composition can be achieved within a day. The lighter isotope (86Sr) is preferentially adsorbed, with the fractionation extent showing no significant change with respect to reaction time, pH, or Sr concentration under low ionic strength conditions (−0.14‰). Equilibrium fractionation processes, rather than Rayleigh fractionation, more accurately represent the isotopic composition trends of dissolved and adsorbed Sr. Experiments in synthetic seawater demonstrated greater Sr isotope fractionation (−0.20‰) compared to low ionic‐strength solutions. This fractionation during adsorption by manganese oxides in synthetic seawater is consistent with the isotopic discrepancy between seawater and ferromanganese nodules, suggesting that Mn oxide adsorption is the primary mechanism for Sr accumulation in ferromanganese deposits. These results imply that ferromanganese deposit Sr isotopic compositions could be proxies for reconstructing seawater Sr isotopic history, which is influenced by carbonate burial and continental weathering, reflecting the global carbon cycle changes.

Alteration of mechanical stresses in the murine brain by age and hemorrhagic stroke.

Residual mechanical stresses, also known as solid stresses, emerge during rapid differential growth or remodeling of tissues, as observed in morphogenesis and tumor growth. While residual stresses typically dissipate in most healthy adult organs, as the growth rate decreases, high residual stresses have been reported in mature, healthy brains. However, the origins and consequences of residual mechanical stresses in the brain across health, aging, and disease remain poorly understood. Here, we utilized and validated a previously developed method to map residual mechanical stresses in the brains of mice across three age groups: 5-7 days, 8-12 weeks, and 22 months. We found that residual solid stress rapidly increases from 5-7 days to 8-12 weeks and remains high in mature 22 months mice brains. Three-dimensional mapping revealed unevenly distributed residual stresses from the anterior to posterior coronal brain sections. Since the brain is rich in negatively charged hyaluronic acid, we evaluated the contribution of charged extracellular matrix (ECM) constituents in maintaining solid stress levels. We found that lower ionic strength leads to elevated solid stresses, consistent with its unshielding effect and the subsequent expansion of charged ECM components. Lastly, we demonstrated that hemorrhagic stroke, accompanied by loss of cellular density, resulted in decreased residual stress in the murine brain. Our findings contribute to a better understanding of spatiotemporal alterations of residual solid stresses in healthy and diseased brains, a crucial step toward uncovering the biological and immunological consequences of this understudied mechanical phenotype in the brain.