Sulfate Analogue Research Articles

Influence of Common Anions on the Coordination of Metal Cations in Polyalcohols

Polyalcohols (polyols), such as ethylene glycol, have mild reducing ability. They are used in the so‐called polyol process to produce metallic nanoparticles of various kinds. In these syntheses, the effective reduction potential of the polyol strongly depends on the presence of other anions. Those anions compete against the polyol molecules for the direct bonding to the metal cations. As an indicator for the coordination behavior of polyols, we crystallized and structurally characterized 19 new coordination compounds with Mn, Co, Ni, Cu, Zn, Cd, Pb, or Bi. 15 of these compounds comprise nitrate ions, the others acetate ions. Compared to the already known chloride and sulfate analogues, nitrate shows an intermediate coordination affinity towards the metal cations considered here. While no direct metal–nitrate coordination occurs with Co2+, Ni2+, and Zn2+, mixed nitrate–polyol coordination environments are found for Mn2+, Cu2+, Cd2+, and Bi3+. Because of its strong chelating property, the acetate ion always coordinates the metal cation, competing with the polyol. The first mononuclear and dinuclear metal acetate diol coordination compounds were obtained with Co2+ and Cu2+, respectively. The coordination affinity of nitrate and acetate ligands in solid metal polyol complexes fully corresponds with our recent observations of the anion‐dependent reduction behavior of copper(II) salts in polyols.

Concise chemoenzymatic synthesis of heparan sulfate analogues as potent BACE-1 inhibitors

Heparan sulfate (HS) and heparin, representative members of the glycosaminoglycans, possess distinct biological functions in terms of their specific interactions with hundreds of binding proteins. However, the structural properties of HS and heparin are complex due to their variable repeating motifs, different chain lengths and sulfation patterns. A concise chemoenzymatic approach has been developed to obtain well-defined low molecular weight (LMW) HS analogues. Pasteurella multocida heparosan synthase-2 (PmHS2) was utilized to fabricate the HS backbones with controllable chain lengths ranging from 14mer to 26mer. Moreover, regioselective and overall sulfation were conducted by chemical approach. The persulfated HS analogues exhibited more potent beta-site amyloid precursor protein (APP)-cleaving enzyme-1 (BACE-1) inhibitory activity than heparin and enoxaparin, and enhanced BACE-1 inhibitions were also found with the increasing molecular size of the HS analogues. This approach supplies the promising LMW HS analogues for the potential development of novel anti-Alzheimer's drugs.

Cross-Species Analysis of Glycosaminoglycan Binding Proteins Reveals Some Animal Models Are "More Equal" than Others.

Glycosaminoglycan (GAG) mimetics are synthetic or semi-synthetic analogues of heparin or heparan sulfate, which are designed to interact with GAG binding sites on proteins. The preclinical stages of drug development rely on efficacy and toxicity assessment in animals and aim to apply these findings to clinical studies. However, such data may not always reflect the human situation possibly because the GAG binding site on the protein ligand in animals and humans could differ. Possible inter-species differences in the GAG-binding sites on antithrombin III, heparanase, and chemokines of the CCL and CXCL families were examined by sequence alignments, molecular modelling and assessment of surface electrostatic potentials to determine if one species of laboratory animal is likely to result in more clinically relevant data than another. For each protein, current understanding of GAG binding is reviewed from a protein structure and function perspective. This combinatorial analysis shows chemokine dimers and oligomers can present different GAG binding surfaces for the same target protein, whereas a cleft-like GAG binding site will differently influence the types of GAG structures that bind and the species preferable for preclinical work. Such analyses will allow an informed choice of animal(s) for preclinical studies of GAG mimetic drugs.

Porcine Circovirus 2 Uses a Multitude of Weak Binding Sites To Interact with Heparan Sulfate, and the Interactions Do Not Follow the Symmetry of the Capsid.

Porcine circovirus 2 (PCV2) is the smallest pathogenic virus capable of autonomous replication within its host. Infections result in immunosuppression and subsequent death of the host and are initiated via the attachment of the PCV2 icosahedral capsid to heparan sulfate (HS) and chondroitin sulfate B (CSB) glycosaminoglycans on the cell surface. However, the underlying mechanism of structural recognition remains to be explored. Using heparin, a routinely used analog of heparan sulfate, we demonstrate that increasing lengths of heparin exhibit a greater affinity toward PCV2. Our competition assays indicate that dextran sulfate (8 kDa) has a higher affinity for PCV2 than heparin (12 kDa), chondroitin sulfate B (41 kDa), hyaluronic acid (1.6 MDa), and dextran (6 kDa). This suggests that polymers high in sulfate content are capable of competing with the PCV2-heparan sulfate interaction and, thus, have the potential to inhibit PCV2 infection. Finally, we visualized the interaction between heparin and the PCV2 capsid using cryo-electron microscopy single-particle analysis, symmetry expansion, and focused classification. The image reconstructions provide the first example of an asymmetric distribution of heparin on the surface of an icosahedral virus capsid. We demonstrate that each of the 60 capsid subunits that generate the T=1 capsid can bind heparin via one of five binding sites. However, not all of the binding sites were occupied by heparin, and only one-third to two-thirds of the binding sites were occupied. The binding sites are defined by arginine, lysine, and polar amino acids. Mutating the arginine, lysine, and polar amino acids to alanine diminished the binding capacity of PCV2 to heparin.IMPORTANCE It has been demonstrated that porcine circovirus 2 (PCV2) attaches to cells via heparan sulfate (HS) and chondroitin sulfate B (CSB) glycosaminoglycans; however, the underlying structural mechanism describing the HS/CSB recognition by PCV2 remains to be explored. We used cryo-electron microscopy with single-particle analysis, symmetry expansion, and focused classification to visualize the interaction between the PCV2 capsid and heparin, an analog of heparan sulfate, to better than 3.6-Å resolution. We observed that the interaction between PCV2 and heparin does not adhere to the icosahedral symmetry of the capsid. To the best of our knowledge, this is the first example where the interaction between heparin and an icosahedral capsid does not follow the symmetry elements of the capsid. Our findings also suggest that anionic polymers, such as dextran sulfate, may act to inhibit PCV2 infection.

Structure-activity relationship of leucyladenylate sulfamate analogues as leucyl-tRNA synthetase (LRS)-targeting inhibitors of Mammalian target of rapamycin complex 1 (mTORC1).

Leucyl-tRNA synthetase (LRS) plays an important role in amino acid-dependent mTORC1 signaling, which is known to be associated with cellular metabolism and proliferation. Therefore, LRS-targeting small molecules that can suppress mTORC1 activation may provide an alternative strategy to current anticancer therapy. In this work, we developed a library of leucyladenylate sulfate analogues by extensively modifying three different pharmacophoric regions comprising adenine, ribose and leucine. Several effective compounds were identified by cell-based mTORC1 activation assays and further tested for anticancer activity. The selected compounds mostly exhibited selective cytotoxicity toward five different cancer cell lines, supporting the hypothesis that the LRS-mediated mTORC1 pathway is a promising alternative target to current therapeutic approaches.

Unravel a neuroactive sHA sulfation pattern with neurogenesis activity by a library of defined oligosaccharides

Sulfated hyaluronic acid (sHA) is chemically synthetic mimetic of glycosaminoglycan (GAG) presenting promising biological functions. Specific sulfation pattern, termed as sulfation code plays critical roles in regulating the binding mode between GAG and proteins. As a structural analogue of chondroitin sulfate (CS), sHA bears much higher molecular weight and is nearly free of other proteoglycan contaminants. These properties make sHA a better bioscaffold to build safer and more functionalized material. However, chemical sulfonation process on naked HA polysaccharide produces random sulfation patterns which makes it difficult in disclosing the SAR. Herein, we utilized sHA and CS oligosaccharides with defined sulfation pattern to unravel the SAR between sHA and neurogenesis. We demonstrate sHA tetrasaccharide bearing 6-O-sulfation (sHA-6S) but not other sulfation patterns bind to growth factors at nanomolar range and promote the neurite outgrowth of rat E18 hippocampal neurons in vitro. Furthermore, synthetic sHA polysaccharide enriched in 6-O-sulfation also promote the hippocampal neurite outgrowth in vitro. Our work provides an effective method to disclose the bioactive sulfation pattern of sHA. Our results indicate that a specific sHA sulfation pattern could direct important physiological processes and open the way for the application of sHA-6S in neuroscience and medicine.

Single-Step Per-O-Sulfonation of Sugar Oligomers with Concomitant 1,6-Anhydro Bridge Formation for Binding Fibroblast Growth Factors.

Many circulating cancer-related proteins, such as fibroblast growth factors (FGFs), associate with glycosaminoglycans-particularly heparan sulfate-at the cell surface. Disaccharide analogues of heparan sulfate had previously been identified as the shortest components out of the sugars that bind to FGF-1 and FGF-2. Taking note of the typical pose of l-iduronic acid, we conceived of per-O-sulfonated analogues of such disaccharides, and devised a single-step procedure for per-O-sulfonation of unprotected sugars with concomitant 1,6-anhydro bridge formation to achieve such compounds through direct use of SO3 ⋅Et3 N as sulfonation reagent and dimethylformamide as solvent. The synthesized sugars based on the oligomaltose backbone bound FGF-1 and FGF-2 mostly at the sub-micromolar level, although the tetrasaccharide analogue achieved low-nanomolar binding with FGF-2.

Visualizing pregnenolone sulfate-like modulators of NMDA receptor function reveals intracellular and plasma-membrane localization

Positive modulators of NMDA receptors are important candidates for therapeutic development to treat psychiatric disorders including autism and schizophrenia. Sulfated neurosteroids have been studied as positive allosteric modulators of NMDA receptors for years, but we understand little about the cellular fate of these compounds, an important consideration for drug development. Here we focus on a visualizable sulfated neurosteroid analogue, KK-169. As expected of a pregnenolone sulfate analogue, the compound strongly potentiates NMDA receptor function, is an antagonist of GABAA receptors, exhibits occlusion with pregnenolone sulfate potentiation, and requires receptor domains important for pregnenolone sulfate potentiation. KK-169 exhibits somewhat higher potency than the natural parent, pregnenolone sulfate. The analogue contains a side-chain alkyne group, which we exploited for retrospective click labeling of neurons. Although the anionic sulfate group is expected to hinder cell entry, we detected significant accumulation of KK-169 in neurons with even brief incubations. Adding a photolabile diazirine group revealed that the expected plasma membrane localization of KK-169 is likely lost during fixation. Overall, our studies reveal new facets of the structure-activity relationship of neurosteroids at NMDA receptors, and their intracellular distribution suggests that sulfated neurosteroids could have unappreciated targets in addition to plasma membrane receptors.

Periodontal reconstruction by heparan sulfate mimetic-based matrix therapy in Porphyromonas gingivalis-infected mice

BackgroundPeriodontitis is a set of chronic inflammatory diseases affecting the supporting structures of the teeth, during which a persistent release of lytic enzymes and inflammatory mediators causes a self-perpetuating vicious cycle of tissue destruction and repair. A matrix-based therapy using a heparan sulfate (HS) analogue called ReGeneraTing Agent (RGTA) replaces destroyed HS by binding to available heparin-binding sites of structural molecules, leading to restoration of tissue homeostasis in several inflammatory tissue injuries, including a hamster periodontitis model. MethodsThe ability of RGTA to restore the periodontium was tested in a model of Porphyromonas gingivalis-infected Balb/cByJ mice. After 12 weeks of disease induction, mice were treated weekly with saline or RGTA (1.5 mg/kg) for 8 weeks. Data were analyzed by histomorphometry. ResultsRGTA treatment restored macroscopic bone loss. This was related to (1) a significant reduction in gingival inflammation assessed by a decrease in infiltrated connective tissue, particularly in cells expressing interleukin 1ß, an inflammatory mediator selected as a marker of inflammation; (2) a normalization of bone resorption parameters, i.e. number, activation and activity of osteoclasts, and number of preosteoclasts; (3) a powerful bone formation reaction. The Sharpey's fibers of the periodontal ligament recovered their alkaline phosphatase coating. This was obtained while P. gingivalis infection was maintained throughout the treatment period. ConclusionsRGTA treatment was able to control the chronic inflammation characteristic of periodontitis and blocked destruction of periodontal structures. It ensured tissue regeneration with recovery of the periodontium's anatomy.

Response of intestinal HT-29 cells to the trichothecene mycotoxin deoxynivalenol and its sulfated conjugates

The sulfated forms of the Fusarium toxin deoxynivalenol (DON), deoxynivalenol-3-sulfate (DON-3-Sulf) and deoxynivalenol-15-sulfate (DON-15-Sulf) were recently described, however little is known about their mechanism of action in mammalian cells. DON-3-Sulf and DON-15-Sulf were taken up by HT-29 colon carcinoma cells, although to a lesser extent compared to DON. All three compounds were found to enhance the intracellular ROS level in the dichlorofluorescein assay (≥ 1μM), even though substantial differences were observed in their cytotoxic potential. In silico modelling highlighted that DON-sulfates do not share the classical mechanism of action of DON, being unable to fit into the ribosomal pocket and trigger the classical ribotoxic stress response. However, DON-3-Sulf and DON-15-Sulf sustained a distinctive proliferative stimulus in HT-29 and activated autophagy. The mechanisms of action of DON-3-Sulf and DON-15-Sulf suggest a potential interplay between the onset of ribosomal inhibition and autophagy activation as an alternative and/or complementary mode of action for DON and its sulfated analogues.

Microenvironmental support for cell delivery to the inner ear

Transplantation of mesenchymal stromal cells (MSC) presents a promising approach not only for the replacement of lost or degenerated cells in diseased organs but also for local drug delivery. It can potentially be used to enhance the safety and efficacy of inner ear surgeries such as cochlear implantation. Options for enhancing the effects of MSC therapy include modulating cell behaviour with customized bio-matrixes or modulating their behaviour by ex vivo transfection of the cells with a variety of genes. In this study, we demonstrate that MSC delivered to the inner ear of guinea pigs or to decellularized cochleae preferentially bind to areas of high heparin concentration. This presents an opportunity for modulating cell behaviour ex vivo. We evaluated the effect of carboxymethylglucose sulfate (Cacicol®), a heparan sulfate analogue on spiral ganglion cells and MSC and demonstrated support of neuronal survival and support of stem cell proliferation.

Efficient solid acid catalysts based on sulfated tin oxides for liquid phase esterification of levulinic acid with ethanol

Tin oxide nanomaterials prepared by hydrothermal synthesis at 100 °C or 140 °C with or without template and further calcination step were modified with sulfate groups by post synthesis treatment. The catalysts were characterized by X-ray powder diffraction (XRD), N2 physisorption, UV Vis spectroscopy, TG analysis, XPS and solid state NMR spectroscopy. The acidity of the materials was characterized by temperature programmed desorption (TPD) of ammonia. The catalytic performance of nanosized SnO2 catalysts and their sulfated analogues was studied in levulinic acid (LA) esterification with ethanol. Sulfated materials show significantly higher activity compared to non-sulfated ones. It was found that the synthesis parameters (temperature, template) for preparation of the parent SnO2 nanoparticles influence significantly their textural properties and have a pronounced effect on the structural characteristics of the obtained sulfated tin oxide based materials and their catalytic performance in levulinic acid esterification. Skipping the calcination step during the preparation of parent SnO2 samples synthesized without template resulted in the formation of new, highly crystalline phase based on hydrated tin(IV) sulfate [Sn(SO4)2.xH2O], tin(IV) bisulfate [Sn(HSO4)4.xH2O] and/or tin(IV) pyrosulfate [Sn(S2O7).xH2O] species in the sulfated nanomaterials with superior catalytic performance. The formation of this new and catalytically very active phase not reported so far in the literature for sulfated tin oxide-based materials is discussed. The catalytically active sites for esterification of levulinic acid with ethanol is suggested to result from the formation of strong Brønsted and Lewis acid sites with high density in the newly registered phase. The results indicate that the chemical structure and catalytic performance of the obtained sulfated tin oxide based materials strongly depend on the treatment of the SnO2 nanoparticles before the sulfation procedure.

Aggregation and charging of sulfate and amidine latex particles in the presence of oxyanions

Electrophoretic mobility and time resolved light scattering are used to measure the effect on charging and aggregation of amidine and sulfate latex particles of different oxyanions namely, phosphate, arsenate, sulfate, and selenate. In the case of negatively charged sulfate latex particles oxyanions represent the coions, while they represent counterions in the case of the positively charged amidine latex. Repulsive interaction between the sulfate latex surface and the coions results in weak ion specific effects on the charging and aggregation. On the other hand the interaction of oxyanions with the amidine latex surface is highly specific. The monovalent dihydrogen phosphate ion strongly adsorbs to the positively charged surface and reverses the charge of the particle. This charge reversal leads also to the restabilization of the amidine latex suspension at the intermediate phosphate concentrations. In the case of dihydrogen arsenate the adsorption to amidine latex surface is weaker and no charge reversal and restabilization occurs. Similar differences are seen between the sulfate and selenate analogues, where selenate adsorbs more strongly to the surface as compared to the sulfate ion and invokes charge reversal. The present results indicate that ion specificity is much more pronounced in the case of counterions.

Different sources of sulfur in diets of adult cats on the urinary parameters and acid-base balance

ABSTRACT: Urolithiasis is a common disorder in the veterinary clinic and is considered as one of the most frequently cause of morbidity. This disorder is closely associated with urinary pH and nutrition plays a key role in the control of this disease, because through dietary manipulation it is possible to modify the urinary pH. Sulfur is considered macroelement with a strong influence on the acid-base status and may be crucial to control urinary pH in cats. The purpose of this study was to evaluate the effects of addition of different sources of sulfur (S) in the diet of cats on the urinary parameters and acid-base balance. Forty-two healthy adult cats were divided into 3 groups, and each group of 14 cats received 7 diets in a complete randomized block design. Calcium sulfate (CaSO4), DL-methionine (DLM) and methionine hydroxy analog (MHA) were added to a control diet in two levels (1.28g S/kg and 2.56g S/kg) to formulate 6 other experimental diets. The acid-base balance was evaluated by hemogasometry in samples of venous blood. The DLM at the highest level and MHA differed of the control diet in relation to urinary pH (P<0.05). Calcium sulfate; although, not differentiated from the control diet, has been shown to alter urinary pH despite its zero electrolyte balance. Apparently, the alkalizing effect of calcium was not sufficient to avoid sulfate acidification of the urine. Treatments showed no alteration of the acid-base balance of the animals and no affect the consumption of the diets.

Halistanol sulfates I and J, new SIRT1-3 inhibitory steroid sulfates from a marine sponge of the genus Halichondria.

Two new analogs of halistanol sulfate (1) were isolated from a marine sponge Halichondria sp. collected at Hachijo-jima Island. Structures of these new halistanol sulfates I (2) and J (3) were elucidated by spectral analyses. Compounds 1-3 showed inhibitory activity against SIRT 1-3 with IC50 ranges of 45.9-67.9, 18.9-21.1 and 21.8-37.5 μM, respectively. X-ray crystallography of the halistanol sulfate (1) and SIRT3 complex clearly indicates that 1 binds to the exosite of SIRT3 that we have discovered in this study.

Citrate-mediated sol–gel synthesis of Al-substituted sulfated zirconia catalysts for α-pinene isomerization

Solid acids are desirable heterogeneous catalysts for green chemistry, with zirconia and its sulfated analogues offering tunable Lewis/Brønsted character. A new route to sulfated ZrO2, and Al-substituted ZrO2 (SO4/AlxZrO2), via carbonization and calcination of metal citrate gels and their subsequent sulfation by (NH4)2SO4 is reported. Structural and acidic properties of these materials were characterized by XRD, Raman, XPS, TGA-MS, N2 porosimetry, and propylamine and pyridine titration. Parent and sulfated materials all adopted the tetragonal zirconia phase, with Al-substitution (evidenced by contraction of the zirconia lattice parameter) at between 0.38–3.50wt% increasing the surface area but decreasing acid strength, accompanied by an overall increase in total acid site loading and Lewis character. Low Al concentrations enhance α-pinene isomerization activity by up to 50% due to the increased acid site loading, however the Turnover Frequency (TOF) remained constant indicating a common active site. The TOF decreased for Al concentrations >3.5wt% due to a further fall in acid strength, manifest as higher selectivity to polycyclic versus monocyclic products.

Sulfated Alginate as a Mimic of Sulfated Glycosaminoglycans: Binding of Growth Factors and Effect on Stem Cell Behavior.

Sulfated glycosaminoglycans (GAGs) are principal elements of the extracellular matrix, where they are involved in a plethora of signaling pathways mainly via interactions with diverse proteins such as growth factors and cytokines. However, the mechanisms that drive these interactions are not yet clear, mostly because of the difficulty to access large quantities of homogeneously sulfated natural GAGs. In this work, GAG mimics are synthesized from readily available alginate with different degrees of sulfation (DS, from 0.8 to 2.6) by simple process. The effect of the DS is determined on the binding of basic fibroblast growth factor (FGF-2). The enzyme-linked immunosorbent assay demonstrates that the binding of FGF-2 is significantly greater for alginates with high DS as compared to unmodified and low sulfated analogs. These results are further applied to engineer FGF-2-loaded substrates for stem cell culturing using the layer-by-layer approach. All films support the attachment and growth of adipose derived stem cells (ADSCs). Noteworthy, highly sulfated alginates maintain the stemness of the ADSCs that exhibit remarkably long filopodia. These results can be exploited in the engineering of novel substrates that induce targeted cell behavior via controlled protein delivery and for tissue engineering constructs applicable in various regenerative approaches.

Antiaging evaluation of a serum containing a heparan sulfate analog and control-released retinol

Antiaging evaluation of a serum containing a heparan sulfate analog and control-released retinol

Identification of function-regulating antibodies targeting the receptor protein tyrosine phosphatase sigma ectodomain.

Receptor tyrosine phosphatase sigma (RPTPσ) plays an important role in the regulation of axonal outgrowth and neural regeneration. Recent studies have identified two RPTPσ ligands, chondroitin sulfate proteoglycans (CSPGs) and heparan sulfate proteoglycans (HSPG), which can modulate RPTPσ activity by affecting its dimerization status. Here, we developed a split luciferase assay to monitor RPTPσ dimerization in living cells. Using this system, we demonstrate that heparin, an analog of heparan sulfate, induced the dimerization of RPTPσ, whereas chondroitin sulfate increased RPTPσ activity by inhibiting RPTPσ dimerization. Also, we generated several novel RPTPσ IgG monoclonal antibodies, to identify one that modulates its activity by inducing/stabilizing dimerization in living cells. Lastly, we demonstrate that this antibody promotes neurite outgrowth in SH-SY5Y cells. In summary, we demonstrated that the split luciferase RPTPσ activity assay is a novel high-throughput approach for discovering novel RPTPσ modulators that can promote axonal outgrowth and neural regeneration.

Crystal structure of dilead(II) oxochromate(VI) oxotellurate(IV).

Reaction of chromium(III) precursors with TeO2 in PbF2/PbO melts in air led to oxidation of chromium(III) to chromium(VI), whereas tellurium remained its oxidation state of IV. In the resulting title compound, Pb2(CrO4)(TeO3), the two types of anions are isolated from each other, hence a double salt is formed. The two independent Pb2+ cations exhibit coordination number nine under formation of very distorted coordination polyhedra [bond-length range = 2.363 (6)-3.276 (7) Å]. The oxochromate(VI) and oxotellurate(IV) anions have tetra-hedral and trigonal-pyramidal configurations, respectively. In the crystal structure, (001) layers of metal cations alternate with layers of TeO32- and CrO42- anions along [001], forming a three-dimensional framework structure. Pb2(CrO4)(TeO3) is isotypic with its sulfate analogue Pb2(SO4)(TeO3) and is comparatively discussed.