Simple Ionic Interaction Research Articles

Synthesis and adsorption performance of functionalized chitosan and carboxyethylsilanetriol hybrids

A novel adsorbent from cationic chitosan derivative and anionic silica precursor was fabricated to remove methylene blue (MB). The hybrid material was prepared from N-guanidinium chitosan acetate (GChi) and carboxyethylsilanetriol sodium salt by a simple ionic interaction followed by sol–gel approach. Multiple characterization methods were used to analyze the morphology and the structure of the well-prepared functionalized material. Batch experiments were conducted to optimize the various operational parameters. The Langmuir isotherm was used to fit the data, and it predicted monolayer adsorption with a maximum capacity of 334 mg g−1. A pseudo-second-order equation fit the adsorption process well. Chitosan/silica hybrids containing carboxylic groups are efficient and cost-effective adsorbents for cationic dyes adsorption from aqueous solutions.

The Na⋅⋅⋅B Bond in NaBH3−: A Different Type of Bond

AbstractA newly introduced Na−B bond in NaBH3− has been a challenge for the chemical bonding community. Here, a series of MBH3− (M=Li, Na, K) species and NaB(CN)3− are studied within the context of quantum chemical topology approaches. The analyses suggest that M–B interaction cannot be classified as an ordinary covalent, dative, or even simple ionic interaction. The interactions are controlled by coulombic forces between the metals and the substituents on boron, for example, H or CN, more than the direct M–B interaction. On the other hand, while the characteristics of the (3, −1) critical points of the bonds are comparable to weak hydrogen bonds, not covalent bonds, the metal and boron share a substantial sum of electrons. To the best of the author's knowledge, the characteristics of these bonds are unprecedented among known molecules. Considering all paradoxical properties of these bonds, they are herein described as ionic‐enforced covalent bonds.

The Na⋅⋅⋅B Bond in NaBH3 - : A Different Type of Bond.

A newly introduced Na-B bond in NaBH3 - has been a challenge for the chemical bonding community. Here, a series of MBH3 - (M=Li, Na, K) species and NaB(CN)3 - are studied within the context of quantum chemical topology approaches. The analyses suggest that M-B interaction cannot be classified as an ordinary covalent, dative, or even simple ionic interaction. The interactions are controlled by coulombic forces between the metals and the substituents on boron, for example, H or CN, more than the direct M-B interaction. On the other hand, while the characteristics of the (3, -1) critical points of the bonds are comparable to weak hydrogen bonds, not covalent bonds, the metal and boron share a substantial sum of electrons. To the best of the author's knowledge, the characteristics of these bonds are unprecedented among known molecules. Considering all paradoxical properties of these bonds, they are herein described as ionic-enforced covalent bonds.

The Control of Drug Release and Vascular Endothelialization after Hyaluronic Acid-Coated Paclitaxel Multi-Layer Coating Stent Implantation in Porcine Coronary Restenosis Model.

Background and ObjectivesHyaluronic acid (HA) is highly biocompatible with cells and the extracellular matrix. In contrast to degradation products of a synthetic polymer, degradation products of HA do not acidify the local environment. The aim of this study was to fabricate an HA-coated paclitaxel (PTX)-eluting stent via simple ionic interactions and to evaluate its effects in vitro and in vivo.Materials and MethodsHA and catechol were conjugated by means of an activation agent, and then the stent was immersed in this solution (resulting in a HA-coated stent). After that, PTX was immobilized on the HA-coated stent (resulting in a hyaluronic acid-coated paclitaxel-eluting stent [H-PTX stent]). Study groups were divided into 4 groups: bare metal stent (BMS), HA, H-PTX, and poly (L-lactide)-coated paclitaxel-eluting stent (P-PTX). Stents were randomly implanted in a porcine coronary artery. After 4 weeks, vessels surrounding the stents were isolated and subjected to various analyses.ResultsSmoothness of the surface was maintained after expansion of the stent. In contrast to a previous study on a PTX-eluting stent, in this study, the PTX was effectively released up to 14 days (a half amount of PTX in 4 days). The proliferation of smooth muscle cells was successfully inhibited (by 80.5±12.11% at 7 days of culture as compared to the control) by PTX released from the stent. Animal experiments showed that the H-PTX stent does not induce an obvious inflammatory response. Nevertheless, restenosis was clearly decreased in the H-PTX stent group (9.8±3.25%) compared to the bare-metal stent group (29.7±8.11%).ConclusionA stent was stably coated with PTX via simple ionic interactions with HA. Restenosis was decreased in the H-PTX group. These results suggest that HA, a natural polymer, is suitable for fabrication of drug-eluting stents (without inflammation) as an alternative to a synthetic polymer.

Specific interaction of the envelope glycoproteins E1 and E2 with liver heparan sulfate involved in the tissue tropismatic infection by hepatitis C virus

The first step in the process of infections by the hepatitis C virus (HCV) is attachment to the host cell, which is assumed to be mediated by interaction of the envelope glycoproteins E1 and E2 with cell surface glycosaminoglycans. In this study, a variety of glycosaminoglycans, heparan sulfate (HS) from various bovine tissues as well as chondroitin sulfate (CS)/dermatan sulfate from bovine liver, were used to examine the direct interaction with recombinant E1 and E2 proteins. Intriguingly, among HS preparations from various bovine tissues, only liver HS strongly bound to both E1 and E2. Since HS from liver, which is the target tissue of HCV, contains highly sulfated structures compared to HS from other tissues, the present results suggest that HS-proteoglycan on the liver cell surface appears to be one of the molecules that define the liver-specific tissue tropism of HCV infection. The interaction assay with chemically modified heparin derivatives provided evidence that the binding of the viral proteins to heparin/HS is not only mediated by simple ionic interactions, but that the 6-O-sulfation and N-sulfation are important. Heparin oligosaccharides equal to or larger than 10-mer were required to inhibit the binding. Notably, a highly sulfated CS-E preparation from squid cartilage also strongly interacted with both viral proteins and inhibited the entry of pseudotype HCV into the target cells, suggesting that the highly sulfated CS-E might be useful as an anti-HCV drug.

A comparative study of two polyelectrolyte complexes

AbstractInterpenetrating polymeric networks (IPNs) based on natural sodium alginate (NaAlg) biopolymer matrix and synthetic hydrophilic polymer were synthesized using sequential method. Poly(acryloxyethyl‐trimethylammonium chloride‐co‐2‐hydroxyethyl methacrylate) (poly(Q‐co‐H)) with high content of quaternary ammonium groups (Q units) was used as a synthetic polymer for the purpose. Since NaAlg has anionic nature and poly(Q‐co‐H) is a polycation polyelectrolyte complex (PEC) was also prepared via ion interaction between these natural and synthetic components by mixing their water solutions. The all prepared materials were characterized by thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (ATR‐FTIR). The comparative analysis of IPNs of different compositions was carried out. Behavior of IPNs was also compared to PEC, material obtained via simple ionic interaction between oppositely charged polymers. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012

Atomic force microscopy evaluation of aqueous interfaces of immobilized hyaluronan

Hyaluronan (HA) was immobilized on aminated glass surfaces in three different ways: by simple ionic interaction and by covalent linking at low density and at full density. In agreement with previous reports, in vitro experiments show that the outcome of fibroblast adhesion tests is markedly affected by the details of the coupling procedure, suggesting that different interfacial forces are operating at the aqueous/HA interface in the three cases investigated. The interfacial properties of the HA-coated surfaces were probed by force–distance curves obtained with the atomic force microscope (AFM). This approach readily shows significant differences among the tested samples, which are directly related to the coupling strategy and to results of cell adhesion tests. In particular, the range of interaction between the tip and the surface is much lower when HA is covalently linked than when it is ionically coupled, suggesting a more compact surface structure in the former case. Increasing HA surface density minimizes the interaction force between the surface and the AFM tip, likely reflecting more complete shielding by the HA chains of the underlying substrate. In summary, these measurements clearly show the different nature of the aqueous interfaces tested, and underline the role of this analytical approach in the development and control of finely tuned biomaterial surfaces.

Thrombin inhibitor design: X-ray and solution studies provide a novel P1 determinant.

The crystal structures of proflavin and 6-fluorotryptamine thrombin have been completed showing binding of both ligands at the active site S1 pocket. The structure of proflavin:thrombin was confirmatory, while the structure of 6-fluorotryptamine indicated a novel binding mode at the thrombin active site. Furthermore, speculation that the sodium atom identified in an extended solvent channel beneath the S pocket may play a role in binding of these ligands was investigated by direct proflavin titrations as well as chromogenic activity measurements as a function of sodium concentration at constant ionic strength. These results suggested a linkage between the sodium site and the S1 pocket. This observation could be due to a simple ionic interaction between Asp189 and the sodium ion or a more complicated structural rearrangement of the thrombin S1 pocket. Finally, the unique binding mode of 6-fluorotryptamine provides ideas toward the design of a neutrally charged thrombin inhibitor.

Purification and properties of a fucoidan-binding protein from human placenta and its identification as immunoglobulin g

1. l. A fucoidan-binding protein from human placenta was purified by affinity chromatography on immobilized fucoidan. 2. 2. Characterization of molecular and immunological properties and peptide mapping indicated that the fucoidan-binding protein is an immunoglobulin G. 3. 3. Cleavage with papain and transblot analysis with labelled fucoidan ascertained binding properties of the f ab fragments. 4. 4. The specificity for fucoidan was furthermore substantiated by hapten inhibition of haemagglutination as well as by solid-phase assays with biotinylated fucoidan as ligand. The results emphasized the importance of structural features instead of simple ionic interactions. 5. 5. Chemical modification with group-specific reagents to lysine, arginine, tryptophan, tyrosine and histidine resulted in substantial inactivation, their impact being markedly reduced by the presence of fucoidan in the cases of lysine, arginine and tryptophan.

Molecular basis of the adhesion ofSalmonellaserotypes to chicken muscle fascia

The adhesion of Salmonella serotypes to chicken muscle fascia was correlated with the ability to be agglutinated by hyaluronan but not by chondroitin sulphate. Agglutination by hyaluronan was not due to simple ionic interaction nor was it inhibited by the sugars tested. Studies with LPS deficient mutants suggested that this component of the bacterial cell wall was not involved in hyaluronan agglutination. Studies using SDS‐PAGE showed that several proteins could bind hyaluronan.

Purification and properties of a Ca2+-independent sialic acid-binding lectin from human placenta with preferential affinity to O-acetylsialic acids

A Ca2+-independent sialic acid-specific lectin from two developmental stages of human placenta was similarly purified to apparent homogeneity by DEAE-cellulose chromatography, affinity chromatography on bovine submaxillary mucin, and gel filtration. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration disclosed a molecular mass of 53 kDa. The specificity of the lectin for O-acetylsialic acids was substantiated by the dependence of hemagglutination on the presence of acetylated sialic acids on the surface of mammalian erythrocytes of various sources, by hapten inhibition in hemagglutination assays with protease-treated rabbit erythrocytes and by hapten inhibition of binding of labeled N-acetylneuraminic acid-bovine serum albumin to the lectin in a solid-phase assay. Bovine and equine submaxillary mucins that contain 9(7,8)-O-acetyl and 4-O-acetylsialic acids were potent inhibitors in contrast to the non-acetylated sialic acids of ovine submaxillary mucin. Absence of inhibitory efficiency of other negatively charged substances like phosphorylated sugars, glucuronic acid, heparin, or oligodeoxynucleotides emphasized the importance of structural features instead of simple ionic interaction. In the presence of acetylation, the pattern of inhibition by gangliosides in the solid-phase assay indicated a preference to alpha-2,8- or alpha-2,6-linked sialic acids in comparison to alpha-2,3-linked moieties. Chemical modification of the lectin by group-specific reagents allowed to emphasize the role of primarily lysine residues, but also, although less pronounced, arginine, tryptophan, and carboxyl groups for ligand binding and/or maintenance of the active conformational state. Application of reagents, specific for histidine or tyrosine residues, failed to affect lectin activity.

Hydrolysis of p-nitrophenyl phenylphosphonate catalysed by bovine pancreatic deoxyribonuclease.

The ability of bovine pancreatic DNAase to hydrolyse the synthetic substrate p-nitrophenyl phenylphosphonate (NPPP) is intrinsic and is not due to the contamination of the DNAase preparation by nonspecific phosphodiesterases because the activities of DNA and NPPP hydrolysis are co-eluted from a DEAE-cellulose column with use of the Ca2+-affinity elution method and because the two activities are decreased simultaneously when the purified enzyme is treated with Cu2+/iodoacetate, an active-site-labelling agent for DNAase. NPPP hydrolysis is facilitated by the metal ion-DNAase. At relatively high Na+ concentrations, where the metal ion-DNA interaction is weak, DNA hydrolysis is also facilitated by the metal ion-DNAase. With NPPP as substrate the Michaelis constants are Km 3.7 mM for Mn2+ and Km 49 mM for Mg2+ in 0.2 M-Tris/HCl buffer, pH 7.2. Ca2+ competes with Mn2+, with Ki 64 mM. Free Cu2+ ions non-competitively inhibit DNAase-catalysed DNA or NPPP hydrolysis in the presence of Mn2+ or Mg2+ and the inhibition is not relieved by Ca2+. The affinity of Cu2+ for free DNAase is higher than that for Mn2+-DNAase. Mn2+ is not bound to DNAase via a simple ionic interaction, as Mn2+ remains bound in the presence of relatively high Na+ concentrations and induces a near-u.v. difference absorption spectrum. The kinetics of NPPP hydrolysis catalysed by Mn2+-DNAase are sigmoidal. From the Hill equation, h = 2.0 is obtained, suggesting that more than two NPPP molecules are bound per molecule of DNAase with a certain amount of co-operativity. Because DNAase in solution is a monomer with a single catalytic site, the multiple NPPP molecules on a single protein molecule are probably in one location, resulting in a co-operative interaction that may resemble that in the stacked base-pairs of double-helical DNA.

Polysaccharide structural features that are critical for the binding of sulfated fucans to bindin, the adhesive protein from sea urchin sperm.

We have investigated the structural features of sulfated fucose-containing polysaccharides which are responsible for their selective binding to Strongylocentrotus purpuratus bindin. The data presented demonstrate that the sulfate esters and a molecular weight in excess of approximately 15,000 are required for high affinity binding of the fucans to bindin. Desulfation destroys the binding activity of the fucans, which can be fully restored by chemical resulfation. Fucan fragments of an average molecular weight of 15,000 were nearly as active as the starting material (Mr 10(6)). The observed IC50 value for fragments of Mr congruent to 10,000 and Mr congruent to 5,000 were 1 and 2 orders of magnitude higher, respectively. The binding of fucoidan to bindin is stable in high salt (50% at 1.2 M NaCl) whereas the binding of fucoidan to DEAE-cellulose or polylysine is inhibited by the concentrations of salt normally found in sea water (50% at 0.2 and 0.5 M NaCl, respectively). This result suggests that the binding mechanism is not a simple ionic interaction and that hydrogen bonding and cooperativity may also be important determinants of the binding mechanism. We also found that polyvinyl sulfate binds to bindin with high affinity and inhibits the bindin-mediated agglutination of sea urchin eggs. The results of these investigations suggest that the spatial orientation of the sulfate esters plays a critical role in determining the selectivity of sulfated polysaccharide binding and that the polysaccharide backbone does not play a direct role in the binding mechanism.

Role of directional Ca 2+ effect on reduced viscosities of mucus secretions from chicken trachea in vitro

Reduced viscosities of fibrillar and gelatinous type mucins produced in response to high submucosal Ca 2+ and low luminal Ca 2+ effects were significantly higher than those of corresponding types of normal mucins. The increased reduced viscosity of experimental mucin samples was due to their aggregation with unique low molecular weight ( M r 325 000 and 46 200) sulphate-rich component. The Ca 2+ appeared to exert two opposing effects on viscosity properties of mucins; whereas Ca 2+ through simple ionic interactions decreased the reduced viscosity of mucins, its ability to promote macromolecular mucin complex formation increased their reduced viscosity. Formation of Ca 2+-dependent complexes between different types of mucins appeared to be a selective phenomenon between sulphate-rich mucins and components. Ester sulphate residue content rather than N-acetylneuraminic acid residue content of these mucins and low molecular weight components showed a very good correlation with their reduced viscosity and Ca 2+-binding values.

Changing patterns of single-stranded-DNA-binding proteins in differentiating brain cortex and cerebellar neurons.

Single-stranded-DNA-binding proteins were analyzed in nuclei of differentiating rat cortex and cerebellar neurons. The developmental period investigated ranged from gestational day 19 (i.e. 3 days before term) to postnatal day 30. During this time both types of neurons undergo transition from proliferating, undifferentiated precursor cells to non-proliferating, terminally differentiated neurons. For comparison, nuclei from mature cortex glia and liver were also examined. Nuclei were isolated according to cell type, the proteins were 14C-labeled in vitro by reductive methylation and were fractionated by affinity chromatography on tandemly arranged columns of double-stranded and single-stranded DNA-cellulose. The columns were uncoupled and the proteins adsorbed to the single-stranded DNA were eluted with salt. They were then analyzed by high resolution two-dimensional gel electrophoresis followed by fluorography. This strategy ensured the selective detection of proteins that recognize single-stranded DNA specifically, and eliminated interference by proteins binding to DNA by simple ionic interaction as well as by proteins with affinity for double-stranded DNA. Many single-stranded-DNA-binding proteins showed conspicuous developmental fluctuations. In cortex neurons these took place around the time of birth and the first postnatal week, whereas in cerebellar neurons they occurred later and in a more protracted fashion. Thus, in both cortex and cerebellar neurons the protein changes followed a time course closely paralleling the arrest of cell division and the beginning of terminal differentiation. It is suggested that this approach may lead to the detection of putative regulatory proteins of the cell nucleus.