Characterization of the anticoagulant actions of a semisynthetic curdlan sulfate

Carboxymethylated Gums and Derivatization: Strategies and Significance in Drug Delivery and Tissue Engineering

Natural polysaccharides have been widely exploited in drug delivery and tissue engineering research. They exhibit excellent biocompatibility and fewer adverse effects; however, it is challenging to assess their bioactivities to that of manufactured synthetics because of their intrinsic physicochemical characteristics. Studies showed that the carboxymethylation of polysaccharides considerably increases the aqueous solubility and bioactivities of inherent polysaccharides and offers structural diversity, but it also has some limitations that can be resolved by derivatization or the grafting of carboxymethylated gums. The swelling ratio, flocculation capacity, viscosity, partition coefficient, metal absorption properties, and thermosensitivity of natural polysaccharides have been improved as a result of these changes. In order to create better and functionally enhanced polysaccharides, researchers have modified the structures and properties of carboxymethylated gums. This review summarizes the various ways of modifying carboxymethylated gums, explores the impact that molecular modifications have on their physicochemical characteristics and bioactivities, and sheds light on various applications for the derivatives of carboxymethylated polysaccharides.

Sulfated Galactans from Gracilaria fisheri with Supplementation of Octanoyl Promote Wound Healing Activity In Vitro and In Vivo

Sulfated galactans (SG) isolated from Gracilaria fisheri is partially degraded (DSG), and subsequentially supplemented with octanoyl (DSGO) and sulfate (DSGS) groups. The molecular weights of DSG, DSGO, and DSGS are 7.87, 152.79, and 97.07 kDa, respectively. The modification is confirmed using FTIR and NMR, while in vitro wound healing activity is assessed using scratched wound fibroblasts. The results reveal that DSGO exhibits highest percentage of wound closure in scratched fibroblast L929 cells. Furthermore, DSGO is able to promote proliferation and accelerate migration of scratched fibroblasts, which correspond to the regulation of proteins and mRNA (Ki67, p-FAK, vimentin, and E-cadherin) determined by Western blotting and qPCR analysis. The superior wound healing activity of DSGO is also confirmed in excision wound of rats. The results demonstrate that DSGO significantly enhances the percentage of wound closure, re-epithelialization, and collagen arrangement, increases α-smoth muscle actin (α-SMA) and vimentin expression, and decreases that of tumor necrosis factor-α (TNF-α) at the wound site. The results suggest that degraded SG supplemented with medium-chain fatty acids of octanoyl group may pass through the membrane, subsequently activating the mediators associated with proliferation and migration of fibroblasts, which can potentially lead to the promotion of wound healing activity.

Cognition of polysaccharides from confusion to clarity: when the next "omic" will come?

With the accelerated pace of modern life, people are facing more and more health pressure. The study of polysaccharides seemed a good choice as a potential treasure trove. Polysaccharides, one of the four basic substances (proteins, nucleic acids, lipids and carbohydrates) that constitute life activities, are obviously an underrated macromolecular substance with great potential. Compared with protein and nucleic acid, the research of polysaccharides is still in the primary stage. The relationship between structure and function of polysaccharides is not clear. In this review, we highlighted the main methods of extraction, purification and structure identification of polysaccharides; summarized their biological activities including immunoregulation, hypoglycemic, anti-tumor, anti-virus, anti-coagulation, and so on. Particularly, the relationship between their structures and activities was described. In addition, the applications of polysaccharides in health food, medicine and cosmetics were also reviewed. This review can help polysaccharide researchers quickly understand the whole process of polysaccharides research, and also provide a reference for the comprehensive utilization of polysaccharides. We need to standardize the research of polysaccharides to make the experimental data more universal, and take it as important references in the review process. Glycomic may appear as the next "omic" after genomic and proteomic in the future. This review provides support for the advancement of glycomics.

Enzymatic Degradation of Gracilariopsis lemaneiformis Polysaccharide and the Antioxidant Activity of Its Degradation Products

Gracilariopsis lemaneiformis polysaccharides (GLP) were degraded using pectinase, glucoamylase, cellulase, xylanase, and β-dextranase into low-molecular-weight polysaccharides, namely, GPP, GGP, GCP, GXP, and GDP, respectively, and their antioxidant capacities were investigated. The degraded GLP showed higher antioxidant activities than natural GLP, and GDP exhibited the highest antioxidant activity. After the optimization of degradation conditions through single-factor and orthogonal optimization experiments, four polysaccharide fractions (GDP1, GDP2, GDP3, and GDP4) with high antioxidant abilities (hydroxyl radical scavenging activity, DPPH radical scavenging activity, reduction capacity, and total antioxidant capacity) were obtained. Their cytoprotective activities against H2O2-induced oxidative damage in human fetal lung fibroblast 1 (HFL1) cells were examined. Results suggested that GDP pretreatment can significantly improve cell viability, reduce reactive oxygen species and malonaldehyde levels, improve antioxidant enzyme activity and mitochondria membrane potential, and alleviate oxidative damage in HFL1 cells. Thus, the enzyme degradation of GLP with β-dextranase can significantly improve its antioxidant activity, and GDP might be a suitable source of natural antioxidants.

Hydrogen Peroxide Effects on Natural-Sourced Polysacchrides: Free Radical Formation/Production, Degradation Process, and Reaction Mechanism-A Critical Synopsis

Numerous reactive oxygen species (ROS) entities exist, and hydrogen peroxide (H2O2) is very key among them as it is well known to possess a stable but poor reactivity capable of generating free radicals. Considered among reactive atoms, molecules, and compounds with electron-rich sites, free radicals emerging from metabolic reactions during cellular respirations can induce oxidative stress and cause cellular structure damage, resulting in diverse life-threatening diseases when produced in excess. Therefore, an antioxidant is needed to curb the overproduction of free radicals especially in biological systems (in vivo and in vitro). Despite the inherent properties limiting its bioactivities, polysaccharides from natural sources increasingly gain research attention given their position as a functional ingredient. Improving the functionality and bioactivity of polysaccharides have been established through degradation of their molecular integrity. In this critical synopsis; we articulate the effects of H2O2 on the degradation of polysaccharides from natural sources. Specifically, the synopsis focused on free radical formation/production, polysaccharide degradation processes with H2O2, the effects of polysaccharide degradation on the structural characteristics; physicochemical properties; and bioactivities; in addition to the antioxidant capability. The degradation mechanisms involving polysaccharide's antioxidative property; with some examples and their respective sources are briefly summarised.

Hybrid Curdlan Poly(γ -Glutamic Acid) Nanoassembly for Immune Modulation in Macrophage

A nanoformulation composed of curdlan, a linear polysaccharide of 1,3-β-linked d-glucose units, hydrogen bonded to poly(γ -glutamic acid) (PGA), was developed to stimulate macrophage. Curdlan/PGA nanoparticles (C-NP) are formulated by physically blending curdlan (0.2 mg mL^-1 in 0.4 m NaOH) with PGA (0.8 mg mL^-1 ). Forster resonance energy transfer (FRET) analysis demonstrates a heterospecies interpolymer complex formed between curdlan and PGA. The ¹ H-NMR spectra display significant peak broadening as well as downfield chemical shifts of the hydroxyl proton resonances of curdlan, indicating potential intermolecular hydrogen bonding interactions. In addition, the cross peaks in ¹ H-¹ H 2D-NOESY suggest intermolecular associations between the OH-2/OH-4 hydroxyl groups of curdlan and the carboxylic-/amide-groups of PGA via hydrogen bonding. Intracellular uptake of C-NP occurs over time in human monocyte-derived macrophage (MDM). Furthermore, C-NP nanoparticles dose-dependently increase gene expression for TNF-α, IL-6, and IL-8 at 24 h in MDM. C-NP nanoparticles also stimulate the release of IL-lβ, MCP-1, TNF-α, IL-8, IL-12p70, IL-17, IL-18, and IL-23 from MDM. Overall, this is the first demonstration of a simplistic nanoformulation formed by hydrogen bonding between curdlan and PGA that modulates cytokine gene expression and release of cytokines from MDM.

Extraction and structural analysis of Angelica sinensis polysaccharide with low molecular weight and its lipid-lowering effect on nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD) is one of the prevalent and typical chronic liver diseases. In this study, we extracted a novel Angelica sinensis polysaccharide (ASP) with low molecular weight (MW) of 3.2 kDa through optimized "one-step" purification process. The major monosaccharide components of ASP were mannose, rhamnose, glucuronic acid, galactose, arabinose, and xylose with weight ratio of 0.23:0.17:14.41:0.39:1.68:0.87, respectively. Herein, "small" ASP could serve as an effective therapeutic option for NAFLD both in free fatty acid-induced L02 models and in high-fat diet-induced mice models. Results revealed that low MW ASP dose-dependently decreased TG, TC in vitro and TG, TC, ALT, HDL-C, and LDL-C in vivo. Oil Red O-positive area and Nile red fluorescence intensity decreased in ASP treatment groups both in vitro and in vivo which suggested ASP could reduce lipid accumulation and fatty regeneration. Hematoxylin-eosin staining results shown a decrease in hepatocytes ballooning indicating that ASP could ameliorate liver lipid degeneration. Briefly, a novel polysaccharide with low MW was successfully obtained which can prospectively act as NAFLD therapy.

Structural Characterization, Antioxidant Activity, and Biomedical Application of Astragalus Polysaccharide Degradation Products

To study the antioxidant capacity of Astragalus polysaccharides (APS) with different molecular weights, we used hydrogen peroxide to degrade original Astragalus polysaccharide (APS0) with an initial molecular weight of 11.03 kDa and obtained three degraded polysaccharides with molecular weights of 8.38 (APS1), 4.72 (APS2), and 2.60 kDa (APS3). The structures of these polysaccharides were characterized by 1H NMR, 13C NMR, FT-IR, and GC/MS. The degradation process did not cause significant changes in the main chain structure of APS. The monosaccharide component of APS before and after degradation was slightly changed. The antioxidant ability in vitro (removing hydroxyl and ABTS radicals and reducing ability) and in cells (superoxide dismutase and malondialdehyde generation) of these polysaccharides is closely related to their molecular weight. If the molecular weight of APS is very high or low, it is not conducive to their activity. Only APS2 with moderate molecular weight showed the greatest antioxidant activity and ability to repair human kidney epithelial (HK-2) cells. Therefore, APS2 can be used as a potential antistone polysaccharide drug.

Improved curdlan production with discarded bottom parts of Asparagus spear

BACKGROUND

This work evaluated the improvement of curdlan production of Agrobacterium sp. ATCC 31749 by using culture medium containing juice of discarded bottom part of green Asparagus spear (MJDA). Curdlan production was carried out using Agrobacterium sp. ATCC 31749 in flasks with different volumes of MJDA and its non-juice-adding control (CK) incubated in shaker at 30 °C, 200 rpm rotation for 168 h.

RESULTS

All MJDA media increased Agrobacterium sp. ATCC 31749 cell mass and enhanced the cells' ability to utilise sucrose, the carbon source for curdlan biosynthesis, and thereby produced higher concentration of curdlan than CK which is used for commercial production of curdlan. After 168 h of fermentation, 10% MJDA produced 40.2 g/l of curdlan whiles CK produced 21.1 g/l. Curdlan production was increased by 90.4% higher in 10% MJDA than CK. Curdlan produced by 10% MJDA contains 1.2 and 1.5 µg/ml of Asparagus flavonoids and saponins respectively as additives which have wide range of health benefits. The mass of sucrose needed to produce 1.0 g curdlan by Agrobacterium sp. ATCC 31749 in CK is 1.7-fold more than in 10% MJDA.

CONCLUSION

The results strongly revealed that 5-10% MJDA is a good curdlan fermentation media which increase curdlan production yield with cheaper cost of production and simultaneously reduce environmental waste resulting from the large scaled discarded bottom parts of green Asparagus spear during Asparagus production.

Effective Immobilization of Agrobacterium sp. IFO 13140 Cells in Loofa Sponge for Curdlan Biosynthesis

Curdlan production by Agrobacterium sp. IFO13140 immobilized on loofa sponge, alginate and loofa sponge with alginate was investigated. There was no statistically-significant difference in curdlan production when the microorganism was immobilized in different matrices. The loofa sponge was chosen because of its practical application and economy and because it provides a high stability through its continued use. The best conditions for immobilization on loofa sponge were 50 mg of cell, 200 rpm and 72 h of incubation, which provided a curdlan production 1.50-times higher than that obtained by free cells. The higher volumetric productivity was achieved by immobilized cells (0.09 g/L/h) at 150 rpm. The operating stability was evaluated, and until the fourth cycle, immobilized cells retained 87.40% of the production of the first cycle. The immobilized cells remained active after 300 days of storage at 4 °C. The results of this study demonstrate success in immobilizing cells for curdlan biosynthesis, making the process potentially suitable for industrial scale-up. Additional studies may show a possible contribution to the reduction of operating costs.

A chemically sulfated polysaccharide derived from Ganoderma lucidum induces mitochondrial-mediated apoptosis in human osteosarcoma MG63 cells

To develop new anticancer agents, we prepared a sulfated polysaccharide (SCGLP1) from the fruiting bodies of Ganoderma lucidum, and the effect of SCGLP1 on human osteosarcoma MG63 cell line was investigated. Our result showed that treatment with SCGLP1 resulted in a significant inhibitory effect on cell proliferation and cell viability of MG63 cells in a dose- and time-dependent manner and caused apoptotic death in MG63 cells through an increase in G0/G1 phase arrest, but had minor cytotoxic effect on human normal osteoblast (NHOst) cells. Western blot analysis identified that SCGLP1-induced apoptosis was associated with an increased protein expression of proapoptotic Bax and Bad, decreased expression of antiapoptotic Bcl-2 and Bcl-XL, loss of mitochondrial membrane potential (Δψm), the release of mitochondrial cytochrome c to cytosol, and cleavage of caspase-9, caspase-3, and poly(ADP-ribose) polymerase (PARP). In addition, pretreatment with the pan-caspase inhibitor (z-VAD-fmk) blocked the SCGLP1-induced apoptosis in MG63 cells. The data indicate that SCGLP1-induced apoptosis is primarily associated with caspase-3- and caspase-9-dependent apoptotic pathway.

Sulfation of Aegle marmelos gum: synthesis, physico-chemical and functional characterization

The present investigation was aimed at optimizing the conditions for preparing sulfated derivative of gum obtained from partially ripe fruits of Aegle marmelos. Elemental analysis, FTIR-ATR and NMR studies confirmed successful sulfation. The ratio of chlorosulfonic acid to pyridine exerted maximum influence on the degree of substitution followed by reaction temperature and reaction time. The sulfated derivative showed higher swelling in both acidic and alkaline pH as compared to unmodified gum. It also possessed higher negative zeta potential, higher viscosity, work of shear, firmness, consistency, cohesiveness and index of viscosity as compared to both unmodified gum as well as sodium alginate. Sulfated derivative was superior to unmodified gum and sodium alginate in terms of antimicrobial and anticoagulant activity. The sulfated sample appears to be a potential substitute over the unmodified gum sample and sodium alginate for modulating physicochemical properties of food and drug release dosage forms.

Designing nonsaccharide, allosteric activators of antithrombin for accelerated inhibition of factor Xa

Antithrombin is a key regulator of coagulation and prime target of heparins, clinically used anticoagulants. Heparins induce a two-step conformational activation of antithrombin, a process that has remained challenging to target with molecules devoid of the antithrombin-binding pentasaccharide DEFGH. Computational screening of a focused library led to the design of two tetra-sulfated N-arylacyl tetrahydroisoquinoline variants as potential nonsaccharide activators of antithrombin. A high yielding synthetic scheme based on Horner-Wadsworth-Emmons or Pictet-Spengler reactions was developed to facilitate the functionalization of the tetrahydoisoquinoline ring, which upon further amidation, deprotection, and sulfation gave the targeted nonsaccharide activators. Spectrofluorometric measurement of affinity displayed antithrombin binding affinities in the low to high micromolar range at pH 6.0, I 0.05, 25 °C. Measurement of second-order rate constants of antithrombin inhibition of factor Xa in the presence and absence of the designed activators showed antithrombin activation in the range of 8-80-fold in the pH 6.0 buffer. This work puts forward 20c, a novel tetra-sulfated N-arylacyl tetrahydroisoquinoline-based molecule, that activates AT only 3.8-fold less than that achieved with DEFGH, suggesting a strong possibility of rationally designing sulfated organic molecules as clinically relevant AT activators.

Homogeneous sulfation of bagasse cellulose in an ionic liquid and anticoagulation activity

Homogeneous sulfation of bagasse cellulose (BC) with chlorosulfonic acid-dimethylformamide was accomplished in an ionic liquid 1-butyl-3-methylimidazolium chloride ([C(4)mim]Cl). The BCS products from the sulfation had degrees of substitution (DS) in the range of 0.52-2.95 and a simultaneous substitution pattern at C-6, C-2 and C-3 positions. The sulfated BCS attained significant anticoagulation activity, causing a dose-dependent prolongation of coagulation time and inhibition of FIIa and FXa activities in human plasma. The anticoagulation activity of BCS showed a positive correlation with DS, and some of the activity indexes exceeded those of heparin.

Preparation and anticoagulation activity of sodium cellulose sulfate

Semi-synthesis of cellulose sulfate sodium (Na-MCS) was carried out by sulfation of microcrystalline cellulose (MCC) with chlorosulfonic acid-dimethylformamide complex as sulfating agent. As shown by FT-IR, NMR spectroscopy, and elemental analysis, the sulfation occurred mainly at C6, partially at C2, and no substitution at C3. The substitution degree ranged from 1.10 to 1.70 and the average molecular weight is between 1.1 and 3.5 x 10(4)Da. The anticoagulant efficacy and its possible mechanism were investigated using in vitro, in vivo coagulation assays and amidolytic tests in comparison with heparin. Results indicated that Na-MCS exhibited higher anticoagulation activity based on activated partial thromboplastin time (APTT) assay and prolonged the thrombin time (TT) to a lesser extent than heparin. No effect was detected on the prothrombin time (PT). Subcutaneous administration of Na-MCS to mice increased the clotting time (CT) in a moderate dose-dependent manner with a longer duration. Na-MCS exhibited anticoagulation activity mainly by accelerating the inhibition of antithrombin III (AT-III) on coagulation factors FIIa and FXa in plasma.

Controlled Release Biopolymers for Enhancing the Immune Response

Controlled release of biologically active compounds in the context of drug and vaccine delivery is an important area of research with broad implications in many areas of medicine. In particular, the challenges of oral delivery are of specific interest to reduce the cost and potential health risks related to parenteral administration of pharmaceuticals and vaccine formulations. We discuss the biological activities of two biopolymers, beta-glucans and emulsans, both of which offer significant potential for individual formulations related to drug impact, while in combination offer synergistic opportunities in terms of formulation and delivery. beta-Glucans have been established as potent immunomodulatory and biologically active compounds with application in a wide range of disease systems. The emulsan family of biopolymers also has significant potential in vaccine and drug delivery based on recent studies. Each of these biopolymers offers exciting opportunities to modulate biological responses via control of chemistry and physical properties achieved during biosynthesis or postsynthesis modifications. When combined into a delivery system for controlled release, synergistic outcomes may be achieved that offer new and exciting opportunities as described in the present paper. These outcomes represent the combined improvements of solubility in physiological environments and immunomodulation due to the specific chemistry and structures involved. Overall, this approach provides a new direction in controlled release wherein the biomaterial carrier, in this case emulsan, and the drug, in this case beta-glucan, play an active role both in biological activation as well as in delivery profiles.

O-palmitoylcurdlan sulfate (OPCurS)-coated liposomes for oral drug delivery

O-Palmitoylcurdlan sulfate (OPCurS) was applied to the liposomal surface to improve the stability of liposomes. To synthesize OPCurS, curdlan was chemically sulfated and then modified with a palmitoyl derivative. The synthesized OPCurS was characterized by Fourier transform-infrared spectroscopy (FT-IR). OPCurS-coated liposomes prepared by the solvent evaporation method were characterized for size, shape, surface charge, and stability in simulated gastric fluid (SGF) and sodium cholate solution. The sizes of OPCurS-coated liposomes increased with the OPCurS content of liposomes and zeta potential decreased when OPCurS was applied to the liposomal surface. With the increase in the content of OPCurS attached to the liposomal surface, the stability of liposomes in SGF and sodium cholate solution was gradually induced and the stability was most improved at a lipid/OPCurS weight ratio of 1.5. Liposomes not coated with OPCurS released 99.5+/-2.3% of the initial 5-carboxyfluorescein (5-CF) content, whereas OPCurS-coated liposomes released 53.7+/-3.7%. OPCurS on the surface of liposomes suppressed the release of 5-CF. Theses results indicate that OPCurS-coated liposomes can be effectively used as a drug delivery carrier via oral administration.

Selectin-blocking semisynthetic sulfated polysaccharides as promising anti-inflammatory agents

Selectin-induced leucocytes rolling along the endothelial surface of blood vessels initiate a complex adhesion cascade, which is an essential step in the cellular immune response. Consequently, blocking the binding between the selectins and their ligands represents a promising strategy for suppressing pathological inflammatory reactions. This study describes the effects of an unfractionated heparin and a low-molecular-weight heparin and a series of structurally well-defined semisynthetic glucan sulfates on selectin-mediated cell-rolling with respect to inhibition. To simulate the blood flow characteristics of postcapillary venules, the rolling experiments were performed in a dynamic-flow-chamber system with immobilized selectins and selectin ligand-carrying U937 cells. The influence of the test compounds on cell rolling was measured by the percentage of adherent cells after a certain flow time and the velocity of the rolling cells. Whereas the test compounds displayed no inhibitory effect on E-selectin-mediated cell rolling, they efficiently blocked the rolling induced by P-selectin. The glucan sulfates were much more active than either unfractionated heparin or low-molecular-weight heparin, or the standard inhibitor Sialyl Lewis(X). Their inhibitory potency turned out to be strongly dependent on various structural parameters, such as sulfation pattern and molecular weight. In conclusion, the semisysnthetic glucan sulfates represent promising candidates in the development of selectin blocking agents.

Partial synthetic glucan sulfates as potential new antithrombotics: a review

Structurally defined sulfated polysaccharides were produced by partial synthesis to develop new antithrombotics as potential heparin alternatives. Glucans of different natural origins were used as starting polymers. The resulting glucan sulfates display pronounced anticoagulant effects; some of them are as active as heparin. According to studies on the structure-activity relationships, besides the molecular weight (MW) and the degree of sulfation (DS), the sulfation pattern and the polysaccharide basic structure are crucial parameters for their anticoagulant potency. Their mode of action differs from that of heparin. Depending on their individual structure, they specifically interfere with various stages of the coagulation process. In vivo, they partly exhibit antithrombotic activity similar to that of heparin. But the in vivo efficacy is not just based on their anticoagulant activity. Their profibrinolytic actions and their strong TFPI-releasing effect may considerably contribute to this overall effect. Due to their manifold interactions with the system of hemostasis, each glucan sulfate shows a structure-dependent, individual action profile. From the investigated glucan sulfates, mainly C2- and C4-sulfated, linear beta-1,3-glucan sulfates with DS > 1.0 and MW between 18 and 50 kDa proved to be most suitable for a potential use as heparin alternatives. The results of this study demonstrate the impact of the various structural parameters on the antithrombotic activity of sulfated polysaccharides. However, the biological actions of sulfated polysaccharides are not limited to hemostasis, but they also show manifold modulating effects on other biological systems. Therefore, the approach of using highly sophisticated carbohydrate drug design might be a possibility to obtain new drugs with specific action profiles.

New antithrombin-based anticoagulants

Clinically used anticoagulants are inhibitors of enzymes involved in the coagulation pathway, primarily thrombin and factor Xa. These agents can be either direct or indirect inhibitors of clotting enzymes. Heparin-based anticoagulants are indirect inhibitors that enhance the proteinase inhibitory activity of a natural anticoagulant, antithrombin. Despite its phenomenal success, current anticoagulation therapy suffers from the risk of serious bleeding. The need for safer and more effective antithrombotic agents clearly exists. The past decade has seen enormous effort directed toward discovering and/or designing new molecules with anticoagulant activity. These new molecules can be classified into (a). antithrombin and its mutants, (b). natural polysaccharides, (c). synthetic modified heparins and heparin-mimics, (d). synthetic oligosaccharides, and (e). synthetic non-sugar antithrombin activators. This review focuses on these efforts in designing or discovering new molecules that act through the antithrombin pathway of anticoagulation.

Effect of (1-->3)- and (1-->4)-linkages of fully sulfated polysaccharides on their anticoagulant activity

Chemically fully sulfated polysaccharides including xylan (-->4Xylbeta-(1-->4)Xylbeta1-->), amylose (-->4Glcalpha-(1-->4)Glcalpha1-->), cellulose (-->4Glcbeta-(1-->4)Glcbeta1-->), curdlan (-->3Glcbeta-(1-->3)Glcbeta1-->) and galactan (-->3Galbeta-(1-->3)Galbeta1-->), which have been isolated from Korean clam, were prepared, and their anticoagulant activity was investigated. The results strongly suggest that the activity might not be depending on anomeric configuration (alpha or beta) or monosaccharide species but on the glycosidic linkage, either (1-->3) or (1-->4). 1H NMR studies of these modified polysaccharides show that the neighboring sulfate groups at the C-2 and C-3 positions might have caused the conformational changes of each monosaccharide from 4C(1) to 1C(4). Furthermore, the effect of 6-sulfate residues on the anticoagulant activity was investigated using a specific desulfated reaction for the chemically fully sulfated polysaccharides. The 6-sulfate group is very important in determining anticoagulant activity of (1-->3)-linked polysaccharides, whereas the activity is not affected by presence or absence of the 6-sulfate group in (1-->4)-linked polysaccharides.

Designing small, nonsugar activators of antithrombin using hydropathic interaction analyses

Conformational activation of antithrombin is a critical mechanism for the inhibition of factor Xa, a proteinase of the blood coagulation cascade, and is typically achieved with heparin, a polyanionic polysaccharide clinically used for anticoagulation. Although numerous efforts have been directed toward the design of better activators, a fundamental tenet of these studies has been the assumed requirement of an oligo- or a polysaccharide backbone. We demonstrate here a concept that small nonsaccharidic nonpolymeric molecules may be rationally designed to interact with and activate antithrombin for enhanced inhibition of factor Xa. The rational design strategy is based on a study of complexes of natural and mutant antithrombins with heparin-based oligosaccharides using hydropathic interaction (HINT) technique, a quantitative computerized tool for analysis of molecular interactions. A linear correlation was observed between the free energy of binding for antithrombinminus signoligosaccharide complexes and the HINT score over a wide range of approximately 13 kcal/mol, indicating strong predictive capability of the HINT technique. Using this approach, a small, nonsugar, aromatic molecule, (minus sign)-epicatechin sulfate (ECS), was designed to mimic the nonreducing end trisaccharide unit DEF of the sequence specific heparin pentasaccharide DEFGH. HINT suggested a comparable antithrombin-binding geometry and interaction profile for ECS and trisaccharide DEF. Biochemical studies indicated that ECS binds antithrombin with equilibrium dissociation constants of 10.5 and 66 microM at pH 6.0, I 0.025, and pH 7.4, I 0.035, respectively, that compare favorably with 2 and 80 microM observed for the natural activator DEF. ECS accelerates the antithrombin inhibition of factor Xa nearly 8-fold demonstrating for the first time that conformational activation of antithrombin is feasible with appropriately designed small nonsugar organic molecules. The results present unique opportunities for de novo activator design based on this first-generation lead.

Development of SPC-ELISA: a new assay principle for the study of sulfated polysaccharide-protein interactions

A sulfated polysaccharide-coating enzyme-linked immunosorbent assay (SPC-ELISA), a new screening assay for the study of interactions between sulfated polysaccharides and proteins, has been developed. Fibrinogen was used as representative for the protein. A microplate is coated with the sulfated polysaccharide to be tested and then incubated with various concentrations of fibrinogen. The bound fibrinogen is quantified by ELISA technique. The assay has been optimized with respect to coating procedure, incubation times, antibody concentrations, and detection conditions. Its capacity was demonstrated using three different sulfated polysaccharides: heparin, a sulfated glucuronogalactan extracted from a red algae, and a semisynthetic xanthan sulfate. Furthermore, the fibrinogen binding of semisynthetic laminarin sulfates with different degrees of sulfation showed good correlation with their anticoagulant effect as measured by fibrinogen clotting time. The intraassay as well as the interassay variations were lower than 8%. The binding properties observed in the SPC-ELISA correlated well with those found utilizing conventional gel permeation chromatography and fibrinogen affinity gel electrophoresis. Compared to these methods, the SPC-ELISA has several advantages: It is more rapid and far easier to perform, allows high throughput screening, and is suitable for automation. Furthermore, it is inexpensive, highly sensitive, and reproducible and has no special equipment requirements. Finally, the method represents the basis for multiple variations with regard to the target proteins as well as the detection methods.