Mobility of Condensed Counterions in Ion-Exchange Membranes: Application of Screening Length Scaling Relationship in Highly Charged Environments

Ion-exchange membranes (IEMs) are widely used in water, energy, and environmental applications, but transport models to accurately simulate ion permeation are currently lacking. This study presents a theoretical framework to predict ionic conductivity of IEMs by introducing an analytical model for condensed counterion mobility to the Donnan-Manning model. Modeling of condensed counterion mobility is enabled by the novel utilization of a scaling relationship to describe screening lengths in the densely charged IEM matrices, which overcame the obstacle of traditional electrolyte chemistry theories breaking down at very high ionic strength environments. Ionic conductivities of commercial IEMs were experimentally characterized in different electrolyte solutions containing a range of mono-, di-, and trivalent counterions. Because the current Donnan-Manning model neglects the mobility of condensed counterions, it is inadequate for modeling ion transport and significantly underestimated membrane conductivities (by up to ≈5× difference between observed and modeled values). Using the new model to account for condensed counterion mobilities substantially improved the accuracy of predicting IEM conductivities in monovalent counterions (to as small as within 7% of experimental values), without any adjustable parameters. Further adjusting the power law exponent of the screen length scaling relationship yielded reasonable precision for membrane conductivities in multivalent counterions. Analysis reveals that counterions are significantly more mobile in the condensed phase than in the uncondensed phase because electrostatic interactions accelerate condensed counterions but retard uncondensed counterions. Condensed counterions still have lower mobilities than ions in bulk solutions due to impedance from spatial effects. The transport framework presented here can model ion migration a priori with adequate accuracy. The findings provide insights into the underlying phenomena governing ion transport in IEMs to facilitate the rational development of more selective membranes

Phenylboronic Acid-Installed Polycarbonates for the pH-Dependent Release of Diol-Containing Molecules

Environmental responsiveness is an appealing trait of emerging polymeric materials, as shown for a variety of pH-responsive drug delivery systems. The chemical versatility of the conjugation site and conjugate lability to physiologically relevant changes in pH will largely determine their applicability. Herein, we report on the use of a drug–polymer complex based on boronic acid-functionalized polycarbonates (PPBC) as the substrate for the pH-sensitive delivery of a diol-containing drug, capecitabine (CAPE). Complexation of CAPE with a PEGylated-PPBC block copolymer, via boronic ester formation, resulted in amphiphiles capable of self-assembling into spherical nanoparticles. We examined nanoparticle stability and release kinetics in neutral and acidic media and relate differences in release profiles and particle stability with changes to polymer chemistry. Comparison of complexed nanoparticles with their noncomplex analogues revealed striking differences in release rate and particle stability. Illustrated herein for capecitabine, the pH-sensitive dissociation of boronate esters from PPBCs can be applied in a general manner to diol- or catechol-containing solutes, demonstrating the utility of these polymers for biomedical applications

Counterion Mobility in Ion-Exchange Membranes: Spatial Effect and Valency-Dependent Electrostatic Interaction

Enhancing the selectivity of ion-exchange membranes (IEMs) is an important need for environmental separations but is hindered by insufficient understanding of the fundamental transport phenomena. Specifically, existing models do not adequately explain the order of magnitude disparity in diffusivities of mono-, di-, and trivalent ions within the membranes. In this study, a transport framework is presented to describe counterion migration mobility using an analytical expression based on first-principles. The two governing mechanisms are spatial effect of available fractional volume for ion transport and electrostatic interaction between mobile ions and fixed charges. Mobilities of counterions with different valencies were experimentally characterized and shown to have high R2s in regression analyses with the proposed transport model. The influence of membrane swelling caused by different counterions was further accounted for to better model the spatial effect. The frictional effect of electrostatic interaction was quantitatively linked to the membrane structural and electrical properties of fixed charged density and dielectric constant. Additionally, the anion-exchange membrane exhibited a weaker electrostatic effect compared to cation-exchange membranes, which was attributed to steric hindrance caused by hydrocarbon chains of the quaternary amine functional groups. The insights offered in this study can inform the rational development of IEMs and membrane processes for ion-specific separations

Nanostructured Films of Ordered Fe Nanowires for High-Performance Transparent Electromagnetic Interference Shielding

Although metal nanowires (NWs), such as silver NWs, are ideal materials for flexible transparent electromagnetic shielding films, the challenge of obtaining absorptive shielding films with high transmittance and shielding efficiency (SE) still exists. To address this issue, this study used iron nanowires (Fe NWs) with excellent microwave absorbing properties to construct structures with ordered NW distributions. A series of polyethylene terephthalate (PET)/Fe NWs/poly (3,4-ethylenedioxythiophene) (PEDOT) electromagnetic interference (EMI) shielding films were prepared using the magnetic-field-induced orientation. The results demonstrate that the ordered Fe NW network structure can effectively overcome the problem of the trade-off between light transmittance and EMI SE. Specifically, at a Fe NW surface density of 201.78 mg/m2, the ordered PET/Fe NWs/PEDOT films demonstrated a 49.06% increase in light transmittance and a 32.94% increase in EMI SE (19.37 dB), compared to the films with randomly distributed Fe NWs. Furthermore, constructing a double-layer Fe NW network with a stagger angle of 45° at the same surface density increased the EMI SE by 73.2% relative to the monolayer-ordered Fe NW structure, reaching an SE value of 33.54 dB, while maintaining almost unchanged light transmittance. Additionally, the PET/Fe NWs/PEDOT films maintain 97.4% of EMI performance after 3000 bending cycles. Overall, this study provides a new approach for creating high-performance flexible transparent EMI shielding films

Nanostructured Films of Ordered Fe Nanowires for High-Performance Transparent Electromagnetic Interference Shielding

Although metal nanowires (NWs), such as silver NWs, are ideal materials for flexible transparent electromagnetic shielding films, the challenge of obtaining absorptive shielding films with high transmittance and shielding efficiency (SE) still exists. To address this issue, this study used iron nanowires (Fe NWs) with excellent microwave absorbing properties to construct structures with ordered NW distributions. A series of polyethylene terephthalate (PET)/Fe NWs/poly (3,4-ethylenedioxythiophene) (PEDOT) electromagnetic interference (EMI) shielding films were prepared using the magnetic-field-induced orientation. The results demonstrate that the ordered Fe NW network structure can effectively overcome the problem of the trade-off between light transmittance and EMI SE. Specifically, at a Fe NW surface density of 201.78 mg/m2, the ordered PET/Fe NWs/PEDOT films demonstrated a 49.06% increase in light transmittance and a 32.94% increase in EMI SE (19.37 dB), compared to the films with randomly distributed Fe NWs. Furthermore, constructing a double-layer Fe NW network with a stagger angle of 45° at the same surface density increased the EMI SE by 73.2% relative to the monolayer-ordered Fe NW structure, reaching an SE value of 33.54 dB, while maintaining almost unchanged light transmittance. Additionally, the PET/Fe NWs/PEDOT films maintain 97.4% of EMI performance after 3000 bending cycles. Overall, this study provides a new approach for creating high-performance flexible transparent EMI shielding films

Table_1_Arginine GlcNAcylation and Activity Regulation of PhoP by a Type III Secretion System Effector in Salmonella.XLSX

Salmonella type III secretion system (T3SS) effector SseK3 is a glycosyltransferase delivered directly into the host cells to modify host protein substrates, thus manipulating host cellular signal transduction. Here, we identify and characterize the Arg-GlcNAcylation activity of SseK3 inside bacterial cells. Combining Arg-GlcNAc protein immunoprecipitation and mass spectrometry, we found that 60 bacterial proteins were GlcNAcylated during Salmonella infection, especially the two-component signal transduction system regulatory protein PhoP. Moreover, the Arg-GlcNAcylation of PhoP by SseK3 was detected in vivo and in vitro, and four arginine residues, Arg65, Arg66, Arg118, and Arg215 were identified as the GlcNAcylation sites. Site-directed mutagenesis showed that the PhoP R215A change significantly reduced the DNA-binding ability and arginine to alanine change at all four sites (PhoP 4RA) completely eliminated the DNA-binding ability, suggesting that Arg215 is essential for the DNA-binding activity of PhoP and GlcNAcylation of PhoP affects this activity. Additionally, GlcNAcylation of PhoP negatively regulated the activity of PhoP and decreased the expression of its downstream genes. Overall, our work provides an example of the intra-bacterial activities of the T3SS effectors and increases our understanding of endogenous Arg-GlcNAcylation.</p

Nanostructured Films of Ordered Fe Nanowires for High-Performance Transparent Electromagnetic Interference Shielding

Although metal nanowires (NWs), such as silver NWs, are ideal materials for flexible transparent electromagnetic shielding films, the challenge of obtaining absorptive shielding films with high transmittance and shielding efficiency (SE) still exists. To address this issue, this study used iron nanowires (Fe NWs) with excellent microwave absorbing properties to construct structures with ordered NW distributions. A series of polyethylene terephthalate (PET)/Fe NWs/poly (3,4-ethylenedioxythiophene) (PEDOT) electromagnetic interference (EMI) shielding films were prepared using the magnetic-field-induced orientation. The results demonstrate that the ordered Fe NW network structure can effectively overcome the problem of the trade-off between light transmittance and EMI SE. Specifically, at a Fe NW surface density of 201.78 mg/m2, the ordered PET/Fe NWs/PEDOT films demonstrated a 49.06% increase in light transmittance and a 32.94% increase in EMI SE (19.37 dB), compared to the films with randomly distributed Fe NWs. Furthermore, constructing a double-layer Fe NW network with a stagger angle of 45° at the same surface density increased the EMI SE by 73.2% relative to the monolayer-ordered Fe NW structure, reaching an SE value of 33.54 dB, while maintaining almost unchanged light transmittance. Additionally, the PET/Fe NWs/PEDOT films maintain 97.4% of EMI performance after 3000 bending cycles. Overall, this study provides a new approach for creating high-performance flexible transparent EMI shielding films

Drastic Enhancement of X‑ray Scattering Contrast between Amorphous and Crystalline Phases of Poly(3-hexylthiophene) at the Sulfur K‑Edge

Semicrystalline semiconducting polymers such as poly­(3-hexylthiophene) exhibit hierarchical molecular ordering that influences their optoelectronic properties. As well as possessing crystalline order on the molecular scale, P3HT also exhibits regular ordering of crystalline lamellae on the nanoscale. This layering of crystalline and amorphous regions is characterized by the so-called “long period” which can be measured with small-angle X-ray scattering (SAXS). The weak scattering contrast between amorphous and crystalline phases generally requires SAXS measurement of bulk powder samples. Here, we show that by utilizing polarized tender X-rays tuned to the sulfur K-edge, strong contrast between amorphous and crystalline phases can be generated allowing for the long period of thin film P3HT samples to be easily observed. Furthermore, we show that the contrast generated results from differences in orientational order in the amorphous and crystalline regions. The use of resonant tender X-ray scattering is thus a promising technique for studying nanoscale ordering not only in semiconducting polymers but also for other soft matter systems

Data_Sheet_1_Arginine GlcNAcylation and Activity Regulation of PhoP by a Type III Secretion System Effector in Salmonella.docx

Salmonella type III secretion system (T3SS) effector SseK3 is a glycosyltransferase delivered directly into the host cells to modify host protein substrates, thus manipulating host cellular signal transduction. Here, we identify and characterize the Arg-GlcNAcylation activity of SseK3 inside bacterial cells. Combining Arg-GlcNAc protein immunoprecipitation and mass spectrometry, we found that 60 bacterial proteins were GlcNAcylated during Salmonella infection, especially the two-component signal transduction system regulatory protein PhoP. Moreover, the Arg-GlcNAcylation of PhoP by SseK3 was detected in vivo and in vitro, and four arginine residues, Arg65, Arg66, Arg118, and Arg215 were identified as the GlcNAcylation sites. Site-directed mutagenesis showed that the PhoP R215A change significantly reduced the DNA-binding ability and arginine to alanine change at all four sites (PhoP 4RA) completely eliminated the DNA-binding ability, suggesting that Arg215 is essential for the DNA-binding activity of PhoP and GlcNAcylation of PhoP affects this activity. Additionally, GlcNAcylation of PhoP negatively regulated the activity of PhoP and decreased the expression of its downstream genes. Overall, our work provides an example of the intra-bacterial activities of the T3SS effectors and increases our understanding of endogenous Arg-GlcNAcylation.</p

Table_2_Arginine GlcNAcylation and Activity Regulation of PhoP by a Type III Secretion System Effector in Salmonella.XLSX

Salmonella type III secretion system (T3SS) effector SseK3 is a glycosyltransferase delivered directly into the host cells to modify host protein substrates, thus manipulating host cellular signal transduction. Here, we identify and characterize the Arg-GlcNAcylation activity of SseK3 inside bacterial cells. Combining Arg-GlcNAc protein immunoprecipitation and mass spectrometry, we found that 60 bacterial proteins were GlcNAcylated during Salmonella infection, especially the two-component signal transduction system regulatory protein PhoP. Moreover, the Arg-GlcNAcylation of PhoP by SseK3 was detected in vivo and in vitro, and four arginine residues, Arg65, Arg66, Arg118, and Arg215 were identified as the GlcNAcylation sites. Site-directed mutagenesis showed that the PhoP R215A change significantly reduced the DNA-binding ability and arginine to alanine change at all four sites (PhoP 4RA) completely eliminated the DNA-binding ability, suggesting that Arg215 is essential for the DNA-binding activity of PhoP and GlcNAcylation of PhoP affects this activity. Additionally, GlcNAcylation of PhoP negatively regulated the activity of PhoP and decreased the expression of its downstream genes. Overall, our work provides an example of the intra-bacterial activities of the T3SS effectors and increases our understanding of endogenous Arg-GlcNAcylation.</p