Polyvalent Anions Research Articles

Polyvalent anion-induced J-aggregation and its use in ratiometric fluorescence tracking of hypotonic in Arabidopsis

J-aggregate dyes have been widely used in biomedicine, chemical engineering, etc., due to their structure and photophysical properties. J-aggregation theory describes the nearest-neighbor molecules' transition dipole moments in a sliding stacking arrangement. However, we found that the intervention of polyvalent anions can induce the J-aggregation of dyes via the intermolecular van der Waals and electrostatic interactions, which is an essential way once overlooked. Experimental results and theoretical calculations revealed that the more negatively charged or large size of anions within a specific range, the more efficiently the dye will form J-aggregates. As an application, the content of polyvalent anion salts in a salt-stressed Arabidopsis model was evaluated based on the ratiometric fluorescence emission resulting from the polyvalent anion-induced dye J-aggregation.

Preparation and stability of pegylated poly(S-alkyl-L-homocysteine) coacervate core micelles in aqueous media.

We report development and preparation of synthetic polypeptide based, coacervate core polyelectrolyte complex micelles, PCMs, in aqueous media, which were characterized and evaluated for the encapsulation and in vitro release of a model single-stranded RNA, polyadenylic acid, poly(A). Cationic, α-helical polypeptides pegylated at their N-termini, PEG113-b-5bn and PEG113-b-5cn, were designed to form coacervate core PCMs upon mixing with multivalent anions in aqueous media. Sodium tripolyphosphate (TPP) and poly(A) were used as model multivalent anions that allowed optimization of polypeptide composition and chain length for formation of stable, nanoscale PCMs. PEG113-b-5c27 was selected for preparation of PCMs that were characterized under different environmental conditions using dynamic light scattering, atomic force microscopy and cryoelectron microscopy. The PCMs were found to efficiently encapsulate poly(A), were stable at physiologically relevant pH and solution ionic strength, and were able to release poly(A) in the presence of excess polyvalent anions. These PCMs were found to be a promising model system for further development of polypeptide based therapeutic delivery vehicles.

Dynamic stability of a crude oil/brine interface: Effect of anion type

The chemical composition of the aqueous phase plays an essential role in water-based enhanced-oil recovery processes. The aqueous phase ionic profile affects the snap-off response of a crude oil-brine system by linking it to the brine-crude oil interfacial rheology. In this work, we focus on the effect of the anion on the snap-off response. To this end, a sample of crude oil from the Minnelusa Sandstone formation in Wyoming was selected, and several aqueous solutions were prepared with salts containing sodium cation and different anions (chlorides, sulfates, and phosphates) at two ionic strength values, 0.6 M and 6 mM, as cases of high- and low-salinity water. Interfacial tension, interfacial viscoelasticity and interface stability were analyzed as functions of aging time using pendant drop, dilatational rheology, and liquid bridge techniques, respectively. Results show that solutions with higher ionic strength led to the formation of more rigid interfaces, i.e. higher elastic modulus, and faster formation kinetics. In the low-salinity regime, solutions with polyvalent anions produce more viscoelastic interfaces at faster rates than solutions with monovalent anions. Finally, an excellent correlation (R2 greater than 0.97) between the relative stability of the interfacial film, predicted in liquid bridge tests, and the ratio of interfacial tension and interfacial elastic modulus was found.

Adsorption Performance of a Multimodal Anion-Exchange Chromatography Membrane: Effect of Liquid Phase Composition and Separation Mode.

Membrane chromatography is a modern, high-throughput separation method that finds important applications in therapeutic protein purification. Multimodal, salt-tolerant membranes are the most recent innovation in chromatographic membrane adsorbents. Due to the complex structure of their ligands and the bimodal texture of their carriers, their adsorption properties have not been sufficiently investigated. This work deals with the equilibrium and kinetic properties of a multimodal anion-exchange chromatography membrane, Sartobind STIC. Single- and two-component adsorption experiments were carried out with bovine serum albumin (BSA) and salmon DNA as model target and impurity components. The effect of the Hofmeister series ions and ionic strength on the BSA/DNA adsorption was investigated in micromembrane flow experiments. A significant difference was observed between the effects of monovalent and polyvalent ions when strong kosmotropic salts with polyvalent anions acted as strong displacers of BSA. On the contrary, DNA binding was rather high at elevated ionic strength, independent of the salt type. Two-component micromembrane experiments confirmed very high selectivity of DNA binding at a rather low sodium sulfate feed content and at pH 8. The strength of binding was examined in more than a dozen different desorption experiments. While BSA was desorbed relatively easily using high salt concentrations independent of buffer type and pH, while DNA was desorbed only in a very limited measure under any conditions. Separation experiments in a laboratory membrane module were carried out for the feed containing 1 g/L of BSA, 0.3 g/L of DNA, and 0.15 M of sodium sulfate. The negative flow-through mode was found to be more advantageous than the bind-elute mode, as BSA was obtained with 99% purity and a 97% yield. Membrane reuse was investigated in three adsorption-desorption-regeneration cycles.

Impact of Arginine–Phosphate Interactions on the Reentrant Condensation of Disordered Proteins

Re-entrant condensation results in the formation of a condensed protein regime between two critical ion concentrations. The process is driven by neutralization and inversion of the protein charge by oppositely charged ions. Re-entrant condensation of cationic proteins by the polyvalent anions, pyrophosphate and tripolyphosphate, has previously been observed, but not for citrate, which has similar charge and size compared to the polyphosphates. Therefore, besides electrostatic interactions, other specific interactions between the polyphosphate ions and proteins must contribute. Here, we show that additional attractive interactions between arginine and tripolyphosphate determine the re-entrant condensation and decondensation boundaries of the cationic, intrinsically disordered saliva protein, histatin 5. Furthermore, we show by small-angle X-ray scattering (SAXS) that polyvalent anions cause compaction of histatin 5, as would be expected based solely on electrostatic interactions. Hence, we conclude that arginine–phosphate-specific interactions not only regulate solution properties but also influence the conformational ensemble of histatin 5, which is shown to vary with the number of arginine residues. Together, the results presented here provide further insight into an organizational mechanism that can be used to tune protein interactions in solution of both naturally occurring and synthetic proteins.

Insight into the mechanism of low molecular weight organic acids-mediated release of phosphorus and potassium from biochars

A crucial mechanism for the application of biochar in soil improvement is the direct release of nutrients from biochar. Low molecular weight organic acids (LMWOAs) ubiquitously exist in soil. However, the mechanism of LMWOAs-mediated release of nutrients from biochars remains little known. Ten biochars with different mineral element stoichiometric ratio were produced, and four LMWOAs [acetic (HAc), glycolic (GA), tartaric (TA), and citric acids (CA)] were employed, to enunciate the influence mechanism of LMWOAs on the release of phosphorus and potassium from biochar. The results showed that HAc suppressed the release of P from biochars, while TA and CA facilitated the release of P from biochars with high ratios of polyvalent metals to P. A new mechanism was proposed that the deprotonated HAc combined with the dissolved HPO42− or H2PO4− to form a complex through hydrogen bond and cation bridging. The hydrophobic methyl group of HAc was exposed outside of the complex, which decreased the water-solubility of phosphate. Meanwhile, a high ratio of polyvalent metals to P benefited more P to combine with polyvalent metals, which decreased the water-solubility of P, but the deprotonated TA and CA are polyvalent anions that could substitute this part of P by anion exchange. Also, LMWOAs promoted the release of K from biochars with low K/(P + S) ratios, possibly due to unionized carboxyl of LMWOAs served as a hydrogen bond donor to displace K out of biochars. This study gives a deep understanding of the fate of biochar originated nutrients response to LMWOAs.

Получение медьсодержащих полимерных комплексов на основе хитозана, перспективных для сельскохозяйственных применений

It is well-known, due to the geological features in a number of regions of the Russian Federation, there may be a shortage of certain microelements and other important “nutrients” in animal diets. The main approach to solve this problem is to use special feed additives. At present, preparations based on organic sources, for example, metal-polymer complexes, are considered a promising alternative. The purpose of this study is to develop an improved method for preparation of the copper-containing polysaccharide complexes and to study their most important parameters. Using CuCl2 as an example, it was shown that the formation of chitosan hydrogels is possible without the usage of potentially hazardous cross-linking agents (for example, glutaraldehyde) or polyvalent anions (for example, SO4 2–), which provide non-covalent cross-linking of chitosan due to electrostatic interactions with NH3 + in its composition. It was found that, upon frontal «gelation» of a 2% chitosan solution (MM 400±100 kDa) in acetic acid (1 vol%), the formation of stable metal gels is observed provided that the content of CuCl2 and ethanol in the precipitant solution is more than 40 mg/ml or more than 24 vol.%, respectively (Vchitosan = Vprecipitant). The obtained complexes are stable in aqueous-alcoholic solutions and swell in water up to destruction (pH 5,5). After additional treatment with an aqueous 1,5% ammonia solution, complexes practically do not swell in solutions with ≥ pH 5,5 (at least τ = 6 days) and dissolve at pH ≤ 4,2. Thus, the use of these complexes is able to provide the release of Cu2 + not in the rumen (pH 6,3–7,2), but in the abomasum (pH ~ 3), which can increase the bioavailability of copper. The development of an improved method for obtaining metal-polysaccharide complexes in a gel form that does not contain «ballast» (in terms of nutritional value and physiology of farm animals) anions (for example, SO4 2–) opens up new opportunities for the development of highly effective feed additives for animal husbandry.

Controlling Phase Separation of Lysozyme with Polyvalent Anions.

The ability of polyvalent anions to influence protein-protein interactions and protein net charge was investigated through solubility and turbidity experiments, determination of osmotic second virial coefficients ( B22), and ζ-potential values for lysozyme solutions. B22 values showed that all anions reduce protein-protein repulsion between positively charged lysozyme molecules, and those anions with higher net valencies are more effective. The polyvalent anions pyrophosphate and tripolyphosphate were observed to induce protein reentrant condensation, which has been previously observed with negatively charged proteins in the presence of trivalent cations. Reentrant condensation is a phenomenon in which low concentrations of polyvalent ions induce protein precipitation, but further increasing polyvalent ion concentration causes the protein precipitate to resolubilize. Interestingly, citrate does not induce lysozyme reentrant condensation despite having a similar charge, size, and shape to pyrophosphate. We observe qualitative differences in protein behavior when compared against negatively charged proteins in solutions of trivalent cations. The polyphosphate ions induce a much stronger protein-protein attraction, which correlates with the occurrence of a liquid-gel transition that replaces the liquid-liquid transition observed with trivalent cations. The results indicate that solutions of polyphosphate ions provide a model system for exploring the link between the protein-phase diagram and model interaction potentials and also highlight the importance that ion-specific effects can have on protein solubility.

Like-charge attraction and opposite-charge decomplexation between polymers and DNA molecules.

We scrutinize the effect of polyvalent ions on polymer-DNA interactions. We extend a recently developed test-charge theory [S. Buyukdagli et al., Phys. Rev. E 94, 042502 (2016)1539-375510.1103/PhysRevE.94.042502] to the case of a stiff polymer interacting with a DNA molecule in an electrolyte mixture. The theory accounts for one-loop level electrostatic correlation effects such as the ionic cloud deformation around the strongly charged DNA molecule as well as image-charge forces induced by the low DNA permittivity. Our model can reproduce and explain various characteristics of the experimental phase diagrams for polymer solutions. First, the addition of polyvalent cations to the electrolyte solution results in the attraction of the negatively charged polymer by the DNA molecule. The glue of the like-charge attraction is the enhanced shielding of the polymer charges by the dense counterion layer at the DNA surface. Second, through the shielding of the DNA-induced electrostatic potential, mono- and polyvalent cations of large concentration both suppress the like-charge attraction. Within the same formalism, we also predict a new opposite-charge repulsion effect between the DNA molecule and a positively charged polymer. In the presence of polyvalent anions such as sulfate or phosphate, their repulsion by the DNA charges leads to the charge screening deficiency of the region around the DNA molecule. This translates into a repulsive force that results in the decomplexation of the polymer from DNA. This opposite-charge repulsion phenomenon can be verified by current experiments and the underlying mechanism can be beneficial to gene therapeutic applications where the control over polymer-DNA interactions is the key factor.

Cloud point behavior of thermosensitive triblock copolymer L61 in the presence of electrolytes

ABSTRACTHerein the effect of additives on the cloud point of thermosensitive copolymer Poly (ethylene oxide)–Poly (propylene oxide)–Poly (ethylene oxide) (PEO–PPO–PEO, L61) was investigated, including NaCl, NaOH, NaBr, Na2CO3, Na3PO4, Na2SO4, Na2HPO4, ZnSO4, FeSO4 and MnSO4 at different concentrations. It was found that the cloud point of L61 was lowered by adding the electrolytes and decreased linearly with increasing electrolytes concentration. In these systems, the addition of polyvalent anions resulted in a more pronounced salting-out effect than monovalent anions. A depression in the cloud point of L61 in the presence of multivalent electrolytes was observed in a trend of > >Cl−. Meanwhile, the ability of divalent anion lower cloud point evaluated by Gibbs free energy was appropriated, and the order as follows: > > . The capacity of divalent cation to reduce the cloud point followed the order Zn2+>Fe2+>Mn2+.

The effects of apolipoprotein B depletion on HDL subspecies composition and function

HDL cholesterol (HDL-C) efflux function may be a more robust biomarker of coronary artery disease risk than HDL-C. To study HDL function, apoB-containing lipoproteins are precipitated from serum. Whether apoB precipitation affects HDL subspecies composition and function has not been thoroughly investigated. We studied the effects of four common apoB precipitation methods [polyethylene glycol (PEG), dextran sulfate/magnesium chloride (MgCl2), heparin sodium/manganese chloride (MnCl2), and LipoSep immunoprecipitation (IP)] on HDL subspecies composition, apolipoproteins, and function (cholesterol efflux and reduction of LDL oxidation). PEG dramatically shifted the size distribution of HDL and apolipoproteins (assessed by two independent methods), while leaving substantial amounts of reagent in the sample. PEG also changed the distribution of cholesterol efflux and LDL oxidation across size fractions, but not overall efflux across the HDL range. Dextran sulfate/MgCl2, heparin sodium/MnCl2, and LipoSep IP did not change the size distribution of HDL subspecies, but altered the quantity of a subset of apolipoproteins. Thus, each of the apoB precipitation methods affected HDL composition and/or size distribution. We conclude that careful evaluation is needed when selecting apoB depletion methods for existing and future bioassays of HDL function.

Improved colorimetric dual-emission and endued piezofluorochromism by inserting a phenyl between 9-anthryl and terpyridine

Tridentate terpyridine is a functional building unit, and 9-anthylterpyridine has been used as ratiometric fluorescent sensor for Cd(II) and secondary sensor for pyrophosphate detection. Here we have inserted a phenyl unit between 9-anthryl and terpyridine to synthesize a new terpyridine derivative, 4-(9-anthryl)phenyl terpyridine (ATP) to investigate the effect of structure change on optical properties. The results show that ATP not only remains the selectively colorimetric fluorescence sensing to Cd2+ but also the interval of two emission bands from ATP and ATP–Cd(II) complex can be enlarged significantly to 185 nm. Unlike 9-anthylterpyridine–Cd(II) complex, ATP–Cd(II) complex could be decomplexed by most polyvalent anions. Moreover, the insertion of a phenyl ring can render ATP–Cd(II) complex remarkable piezofluorochromism with grinding-induced spectral shift of 54 nm. X-ray diffraction and differential scanning calorimetry experiments confirm the phase transformation between crystalline and amorphous states upon external stimuli is responsible for reversible PFC behavior.

Sulfobutylether-β-cyclodextrin/chitosan nano- and microparticles and their physicochemical characteristics

Metastable polymer/cyclodextrin nano- and microparticles (NPs) were prepared from low molecular weight chitosan (CS), Mw about 10kDa, and sulfobutylether β-cyclodextrin (SBEβCD). CS is a cationic polysaccharide containing numerous protonated amino groups (pKa about 6.5). SBEβCD is a β-cyclodextrin derivative with six to seven negatively charged sulfobutyl ether groups per cyclodextrin molecule. Ionotropic gelation technique was used to prepare the NPs. The NP matrix was composed of low molecular weight cationic CS polysaccharide cross-linked with polyvalent anions (SBEβCD). The diameter of the NPs ranged from 200 to almost 1000nm and was controlled by the CS:SBEβCD molar ratio during NP preparation. Hydrocortisone (HC) is a lipophilic drug with limited aqueous solubility (0.3mg/ml). HC displayed AL-type phase-solubility diagrams in aqueous solutions containing either SBEβCD or CS, although CS had negligible solubilizing effect. The ability of the NPs to encapsulate HC decreased with increasing CS concentration during preparation of the NPs even though the SBEβCD content of the NPs increased with increasing CS concentration. This decrease in HC encapsulation was related to the concentration; the ionic crosslinking provides better encapsulation at low initial SBEβCD and CS concentrations.

Acute depletion of plasma membrane phospholipids—dissecting the roles of PtdIns(4)P and PtdIns(4,5)P2

Acute depletion of plasma membrane phospholipids—dissecting the roles of PtdIns(4)P and PtdIns(4,5)P2

Palladium in the Gap: Cluster Assemblies with Band Edges Localized on Linkers

Cluster-assembled materials composed of [Pd2As14]4– polyvalent anions, where a palladium dimer links two As7 clusters, have been synthesized in zero- and two-dimensional architectures. Their dimensionality was controlled through the selection of the counterions, and their structures were characterized by single-crystal X-ray diffraction. Reflectance spectroscopy measurements indicate that the zero- and two-dimensional assemblies have band gaps of 1.35 and 1.15 eV, respectively, and are smaller than the 1.80 eV gap of the As73– cluster. Theoretical investigations reveal that the frontier orbitals of the cluster building blocks are located primarily on the Pd dimer. Further, these orbitals are embedded inside the intrinsic band gap of the As73– clusters, reducing the band gap energy with edge states that are localized on the Pd sites. It is suggested that such a periodic array of narrow localized states may lead to interesting transport and optical properties as the carriers may become localized at these sites.

Analysis of the Bacterial Luciferase Mobile Loop by Replica-Exchange Molecular Dynamics

Bacterial luciferase contains an extended 29-residue mobile loop. Movements of this loop are governed by binding of either flavin mononucleotide (FMNH 2) or polyvalent anions. To understand this process, loop dynamics were investigated using replica-exchange molecular dynamics that yielded conformational ensembles in either the presence or absence of FMNH 2. The resulting data were analyzed using clustering and network analysis. We observed the closed conformations that are visited only in the simulations with the ligand. Yet the mobile loop is intrinsically flexible, and FMNH 2 binding modifies the relative populations of conformations. This model provides unique information regarding the function of a crystallographically disordered segment of the loop near the binding site. Structures at or near the fringe of this network were compatible with flavin binding or release. Finally, we demonstrate that the crystallographically observed conformation of the mobile loop bound to oxidized flavin was influenced by crystal packing. Thus, our study has revealed what we believe are novel conformations of the mobile loop and additional context for experimentally determined structures.

Stabilization and swelling of hagfish slime mucin vesicles

When agitated, Atlantic hagfish (Myxine glutinosa) produce large quantities of slime that consists of hydrated bundles of protein filaments and membrane-bound mucin vesicles from numerous slime glands. When the slime exudate contacts seawater, the thread bundles unravel and the mucin vesicles swell and rupture. Little is known about the mechanisms of vesicle rupture in seawater and stabilization within the gland, although it is believed that the vesicle membrane is permeable to most ions except polyvalent anions. We hypothesized that the most abundant compounds within the slime gland exudate have a stabilizing effect on the mucin vesicles. To test this hypothesis, we measured the chemical composition of the fluid component of hagfish slime exudate and conducted functional assays with these solutes to test their ability to keep the vesicles in a condensed state. We found K(+) concentrations that were elevated relative to plasma, and Na(+), Cl(-) and Ca(2+) concentrations that were considerably lower. Our analysis also revealed high levels of methylamines such as trimethylamine oxide (TMAO), betaine and dimethylglycine, which had a combined concentration of 388 mmol l(-1) in the glandular fluid. In vitro rupture assays demonstrated that both TMAO and betaine had a significant effect on rupture, but neither was capable of completely abolishing mucin swelling and rupture, even at high concentrations. This suggests that some other mechanism such as the chemical microenvironment within gland mucous cells, or hydrostatic pressure is responsible for stabilization of the vesicles within the gland.

Effect of salts on the formation and properties of microcrystalline cellulose and chitosan gels 10th EWLP, Stockholm, Sweden, August 25–28, 2008

Abstract The difference in the effect of salts on the formation and properties of gels based on microcrystalline cellulose (MCC) and microcrystalline chitosan (MCCh) was investigated. Bleached sulphate pulp from wood and chitosan obtained from exoskeletons of crustaceans served as raw materials. These were destructed by a thermocatalytic method to the levelling-off degree of polymerisation and then dispersed in solutions of different salts. At a sufficiently high concentration, gels with a liquid crystalline structure were formed. For MCC, the gels are stronger when the dispersion solution contains polyvalent cations, which decrease the negative charge on the cellulose surface caused by the carboxyl groups present there. As a result, the mutual repulsing forces between the cellulose particles decrease and the lattice formed by them becomes stronger. For MCCh, strong gels with a great viscosity are formed when the dispersion solution contains polyvalent anions, which decrease the positive charge on the chitosan surface caused by amine groups. The effect of salts depends also on their concentration in the solution.

Hybrid Anion Exchange Fibers with Dual Binding Sites: Simultaneous and Reversible Sorption of Perchlorate and Arsenate

When multiple trace contaminants of significantly different chemical properties are present in a single source of contaminated water, designing an engineered sorbent for their simultaneous removal poses a major challenge. Physical–chemical properties of the sorption sites need to be tailored and expanded for preferential binding of more than one contaminant in such cases. The scientific challenge becomes increasingly complex when the sorbent requires to be reusable through intermittent regenerations. In this study, hydrated Fe(III) oxide or HFO nanoparticles were dispersed within an ion exchange fiber containing covalently attached quaternary ammonium functional groups. The resulting hybrid anion exchange fiber (HAIX-F) showed very high sorption affinity for both perchlorate and arsenate in the presence of orders of magnitude greater concentrations of competing sulfate and chloride anions. A series of experimental studies validated that relatively hydrophobic perchlorate was selectively bound to quaternary ammonium functional groups while arsenate uptake took place onto HFO surfaces through ligand exchange. The most significant finding of the study was that perchlorate and arsenate could be desorbed efficiently but separately from each other in a simple-to-operate two-step regeneration using conventional regenerants, namely, sodium hydroxide and sodium chloride solutions. In contrast, spherical anion exchange resins are not amenable to such high regeneration efficiency for perchlorate due to significantly longer diffusion path lengths. The unique sorption and desorption behaviors of HAIX-F can be easily extended to other applications where hydrophobic or polyvalent anions [e.g., pentachlorophenate, uranium(VI) oxyanion, benzenesulfonate] are simultaneously present with environmentally significant ligands, such as phosphate, oxalate, vanadate.

Extracellular DNA and F-actin as targets in antibiofilm cystic fibrosis therapy

Evaluation of: Parks QM, Young RL, Poch KR, Malcolm KC, Vasil ML, Nick JA: Neutrophil enhancement of Pseudomonas aeruginosa biofilm development: human F-actin and DNA as targets for therapy. J. Med. Microbiol. 58(4), 492–502 (2009). Pseudomonas aeruginosa infection and biofilm formation in the cystic fibrosis lung occurs in association with an exuberant inflammatory response in a neutrophil-rich environment. The presence of DNA/F-actin bundles, formed by components released from necrotic neutrophils, was shown to stimulate biofilm formation by P. aeruginosa. Soluble polyvalent anions can sequester polyvalent cations and dissolve DNA/F-actin bundles, and treatment with polyvalent anions was shown to disrupt neutrophil-induced P. aeruginosa biofilms. In addition, polyvalent anions could also prevent the formation of neutrophil-induced P. aeruginosa biofilms. While young neutrophil-induced P. aeruginosa biofilms could be disrupted by treatment with polyvalent anions or DNase, older neutrophil-induced biofilms, or biofilms formed by a mucoid P. aeruginosa variant, were less susceptible to treatment with polyvalent anions or DNase, but they could be efficiently disrupted by polyvalent anion–DNase combination treatment. The synergistic effect of the combined polyvalent anion–DNase treatment is most likely due to the capacity of polyvalent anions to dissociate DNA/F-actin bundles with bacteria and polysaccharides, leading to exposure of a greater number of DNase cleavage sites on the extracellular DNA. It is conceivable that treatment with soluble polyvalent anions as an adjunct to DNase treatment will represent an improvement in cystic fibrosis therapy.