A highly stable covalent conjugated heparin biochip for heparin-protein interaction studies.
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Albumins↗
Biomedical subjects
Robert J Linhardt
Publications and source records attributed to Robert J Linhardt.
Human single chain antibodies against heparin: selection, characterization, and effect on coagulation.
Heparin, located in mast cells and basophilic granulocytes, is widely used as an anticoagulant. It belongs to a class of linear polysaccharides called glycosaminoglycans (GAGs). Using phage display technology, we have selected 19 unique human antiheparin antibodies. Some antibodies react almost exclusively with heparin, others also react with the structurally related heparan sulfate, and some with chondroitin sulfate. In all cases, sulfate groups are essential for binding. For activity of some antibodies, O-sulfation is more important than N-sulfation. Antibodies are reactive with heparin in mast cells. Each antibody showed a defined staining pattern on cryosections of rat kidney, pancreas, and testis. Enzymatic digestion with glycosidases on tissue sections further indicated that the antibodies are specific for GAGs. All antibodies recognize a unique epitope. The effect of the antibodies on heparin as an anticoagulant was also studied. There were 3 antibodies that were very effective inhibitors of heparin action in the activated partial thromboplastin time (APTT) clotting assay, and their effect was related to the amount of heparin bound. Some antibodies reacted strongly with the pentasaccharide, which interacts with antithrombin III. The human antibodies selected represent unique tools to study the structure, location, and function of heparin and related GAGs, and some may be used as blocking agents.
Animals↗
Pretreatment procedure for the microdetermination of chondroitin sulfate in plasma and urine.
A new, simple, and rapid pretreatment method for the determination of chondroitin sulfate, dermatan sulfate, and hyaluronan from urine and blood plasma samples has been developed. Plasma proteins were first converted into small peptides by digestion using a nonspecific protease, actinase E, and the resulting small peptides were removed by centrifugal filtration. The retained, residual crude glycosaminoglycans, including chondroitin/dermatan sulfates and hyaluronan, were converted into unsaturated disaccharides through the action of chondroitin sulfate lyses. Next, these disaccharides were recovered and purified using centrifugal filtration together with DeltaDi-UA2S, added as an internal standard. The filtered disaccharide mixture was analyzed by HPLC with fluorometric postcolumn derivatization using 2-cyanoacetamide as a fluorogenic reagent. This method was applied to a pharmacokinetic study of chondroitin sulfate administered intravenously to mice. The half-life of the administered chondroitin sulfates, having molecular masses from 6 to 50 kDa, varied depending on their molecular sizes. This new method should be useful for studies on the metabolic fate of exogenously administered glycosaminoglycans in small experimental animals.
Animals↗
Structural studies on kappa-carrageenan derived oligosaccharides.
Oligosaccharides were prepared through mild hydrochloric acid hydrolysis of kappa-carrageenan from Kappaphycus striatum carrageenan. Three oligosaccharides were purified by strong-anion exchange high-performance chromatography. Their structure was elucidated using mass spectral and NMR data. Negative-ion electrospray ionization (ESI) mass spectra at different fragmentor voltages provided the molecular weight of the compounds and unraveled the fragmentation pattern of the kappa-carrageenan oligosaccharides. 2D NMR techniques, including 1H-(1)H COSY, 1H-(1)H TOCSY and 13C-(1)H HMQC, were performed to determine the structure of a trisulfated pentasaccharide. 1D NMR and ESIMS were used to determine the structures of a kappa-carrageenan-derived pentasaccharide, heptasaccharide, and an undecasaccharide. All the oligosaccharides characterized have a 4-O-sulfo-D-galactopyranose residue at both the reducing and nonreducing ends.
Carbohydrate Conformation↗
Determination of the composition of the oligosaccharide phosphate fraction of Pichia (Hansenula) holstii NRRL Y-2448 phosphomannan by capillary electrophoresis and HPLC.
The promising new anticancer agent, PI-88, is prepared by the sulfonation of the oligosaccharide phosphate fraction of the extracellular phosphomannan produced by the yeast Pichia (Hansenula) holstii NRRL Y-2448. The composition of the oligosaccharide phosphate fraction was determined by capillary electrophoresis (CE) with indirect UV detection using 6 mM potassium sorbate at pH 10.3 as the background electrolyte. Further confirmation of the composition was obtained by HPLC analysis of a sample dephosphorylated by treatment with alkaline phosphatase. The structure of the hexasaccharide component has been determined by isolation and NMR spectroscopic analysis of its dephosphorylated derivative. Additionally, the structure of a second, previously undetected tetrasaccharide component (a hexosamine) has been determined by isolation and NMR spectroscopic analysis of the acetate of its dephosphorylated derivative. It is demonstrated that CE is an ideal method for the quality control of the oligosaccharide phosphate fraction for use in the production of PI-88.
Antineoplastic Agents↗
Heparin-protein interactions.
Heparin, a sulfated polysaccharide belonging to the family of glycosaminoglycans, has numerous important biological activities, associated with its interaction with diverse proteins. Heparin is widely used as an anticoagulant drug based on its ability to accelerate the rate at which antithrombin inhibits serine proteases in the blood coagulation cascade. Heparin and the structurally related heparan sulfate are complex linear polymers comprised of a mixture of chains of different length, having variable sequences. Heparan sulfate is ubiquitously distributed on the surfaces of animal cells and in the extracellular matrix. It also mediates various physiologic and pathophysiologic processes. Difficulties in evaluating the role of heparin and heparan sulfate in vivo may be partly ascribed to ignorance of the detailed structure and sequence of these polysaccharides. In addition, the understanding of carbohydrate-protein interactions has lagged behind that of the more thoroughly studied protein-protein and protein-nucleic acid interactions. The recent extensive studies on the structural, kinetic, and thermodynamic aspects of the protein binding of heparin and heparan sulfate have led to an improved understanding of heparin-protein interactions. A high degree of specificity could be identified in many of these interactions. An understanding of these interactions at the molecular level is of fundamental importance in the design of new highly specific therapeutic agents. This review focuses on aspects of heparin structure and conformation, which are important for its interactions with proteins. It also describes the interaction of heparin and heparan sulfate with selected families of heparin-binding proteins.
Heparin↗
The effect of dissolved oxygen (DO) concentration on the glycosylation of recombinant protein produced by the insect cell-baculovirus expression system.
The effect of dissolved oxygen concentration on human secreted alkaline phosphatase (SEAP) glycosylation by the insect cell-baculovirus expression system was investigated in a well-controlled bioreactor. Oligomannose-type N-linked glycans (i.e., Man2 to Man6 and Man3F) were present in SEAP produced by Spodoptera frusiperda Sf-9 (Sf-9) and Trichoplusia ni BTI-Tn-5B1-4 (Tn-5B1-4) insect cell lines. The relative amounts of the most highly processed glycans (i.e., Man3F and Man2 in the SEAP from Sf-9 and Tn-5B1-4 cells, respectively) were significantly higher at 50% of air saturation than at either 10% or 190% of air saturation. That is, glycan processing was inhibited at both low and high dissolved oxygen concentrations.
Alkaline Phosphatase↗
Capillary electrophoresis for the analysis of glycosaminoglycans and glycosaminoglycan-derived oligosaccharides.
Glycosaminoglycans are a family of polydisperse, highly sulfated complex mixtures of linear polysaccharides that are involved in many life processes. Defining the structure of glycosaminoglycans is an important factor in elucidating their structure-activity relationship. Capillary electrophoresis has emerged as a highly promising technique consuming an extremely small amount of sample and capable of rapid, high-resolution separation, characterization and quantitation of analytes. Numerous capillary electrophoresis methods for analysis of intact glycosaminoglycans and glycosaminoglycan-derived oligosaccharides have been developed. These methods allow for both qualitative and quantitative analysis with a high level of sensitivity. This review is concerned with separation methods of capillary electrophoresis, detection methods and applications to several aspects of research into glycosaminoglycans and glycosaminoglycan-derived oligosaccharides. The importance of capillary electrophoresis in biological and pharmaceutical samples in glycobiology and carbohydrate biochemistry and its possible applications in disease diagnosis and monitoring chemical synthesis are described.
Carbohydrate Conformation↗
Enhancement of paracellular transport of heparin disaccharide across Caco-2 cell monolayers.
The enhancement of paracellular transport of heparin disaccharide using several absorption enhancers across Caco-2 cell monolayers was tested. The cytotoxicity of these enhancers was also examined. The enhancing effects by Quillaja saponin, dipotassium glycyrrhizinate, 18beta-glycyrrhetinic acid, sodium caprate and taurine were determined by changes in transepithelial electrical resistance (TEER) and the amount of heparin disaccharide transported across Caco-2 cell monolayers. Among the absorption enhancers, 18beta-glycyrrhetinic acid and taurine decreased TEER and increased the permeability of heparin disaccharide in a dose-dependent and time-dependent manner with little or negligible cytotoxicity. Our results indicate that these absorption enhancers can widen the tight junction, which is a dominant paracellular absorption route of hydrophilic compounds. It is highly possible that these absorption enhancers can be applied as pharmaceutical excipients to improve the transport of macromolecules and hydrophilic drugs having difficulty in permeability across the intestinal epithelium.
Absorption↗
Preparation and anticoagulant activity of the phosphosulfomannan PI-88.
A yeast-derived phosphomannan mixture was chemically sulfonated and the composition and structure of the product mixture was studied. This phosphosulfomannan mixture, PI-88, is currently under clinical evaluation as an anti-cancer agent. Analysis using capillary electrophoresis demonstrated that PI-88 was a multi-component mixture. Gel permeation chromatography provided four fractions of PI-88 that contained components which differed in size from disaccharide to hexasaccharide, and by degree of sulfation. These fractions were characterised by spectroscopic and chromatographic methods and the structure of PI-88 is that expected based on the structure of the phosphomannan starting material. The anticoagulant activity of these fractions was evaluated and the structural requirements for activity are described.
Anticoagulants↗
Tissue distribution of [14C]sucrose octasulfate following oral administration to rats.
PURPOSE: Aluminum sucrose octasulfate (SOS) is used clinically to prevent ulcers. Under physiologic conditions, the sodium salt of this drug can be formed. Our objective was to determine whether sodium SOS was absorbed when administered orally. In addition to furthering our understanding of aluminum SOS, this study also aimed to clarify how other polyanionic drugs, such as heparin and low-molecular-weight heparins, are absorbed. METHODS: [14C]-labeled and cold sodium SOS (60 mg/kg) were given to rats by stomach tube. Radioactivity was counted in gut tissue, gut washes, and nongut tissue (i.e., lung, liver, kidney, spleen, endothelial, and plasma samples) at 3 min, 6 min, 15 min, 30 min, 60 min, 4 h, and 24 h, and in urine and feces accumulated over 4 h and 24 h. RESULTS: Peak radioactivity was found in the tissue and washes of the stomach, ileum, and colon at 6 min, 60 min, and 4 h, respectively, showing progression through the gut. Gut recovery accounted for 84% of the dose at 6 min but only 12% of the dose at 24 h, including counts from feces. Radioactivity was recovered from nongut tissue (averaging 8.6% of the dose) and accumulated urine (18% of the dose at 24 h). When total body distribution was considered, the recovery of radioactivity was greater for the endothelium than for plasma (peak percentage of the dose was 65% at 15 min, 20% at 3 min, 5% from 20 to 240 min for the vena cava, aortic endothelium, and plasma, respectively). CONCLUSIONS: Results indicate that sodium SOS is absorbed, agreeing with previous studies demonstrating the oral absorption of other sulfated polyanions. Endothelial concentrations must be considered when assessing the pharmacokinetics of these compounds. The measured plasma drug concentrations reflect the much greater amounts of drug residing with the endothelium.
Administration, Oral↗
Characterization of heparin binding by a peptide from amyloid P component using capillary electrophoresis, surface plasmon resonance and isothermal titration calorimetry.
Synthetic peptides based on amino-acid residues 27-38 of human serum amyloid P component represent a novel type of heparin binders as they do not contain clusters of basic amino acids or other known features associated with protein or peptide heparin binding. Here, we characterize the binding using capillary electrophoresis (CE), surface plasmon resonance (SPR), and isothermal titration calorimetry (ITC). By CE, heparin-binding activity was readily apparent for both a regular peptide and a slightly N-terminally modified form, while a sequence-scrambled peptide had no measurable binding. Dissociation constants in the 1-15 microm range were estimated, but only a minor part of the binding isotherm was covered by the experiments. SPR measurements using immobilized peptides verified heparin binding, the range of the binding constants, and the reduced binding of the sequence-scrambled peptide. Structurally defined heparin oligosaccharides were used to establish that while the tetrasaccharide is too small to exhibit strong binding, little difference in binding strength is observed between hexa- and tetradeca-saccharides. These experiments also confirmed the almost complete lack of activity of the sequence-scrambled peptide. The amino-acid sequence-dependent binding and the importance of a disulfide bond in the peptide were verified by ITC, but the experimental conditions had to be modified because of peptide precipitation and ITC yielded significantly weaker binding constants than the other methods. While the precise function of the peptide in the intact protein remains unclear, the results confirm the specificity of the glycosaminoglycan interaction with regard to peptide sequence by applying two additional biophysical techniques and showing that the N-terminal part of the peptide may be modified without changing the heparin binding capabilities.
Binding Sites↗
Structural basis for activation of fibroblast growth factor signaling by sucrose octasulfate.
Sucrose octasulfate (SOS) is believed to stimulate fibroblast growth factor (FGF) signaling by binding and stabilizing FGFs. In this report, we show that SOS induces FGF-dependent dimerization of FGF receptors (FGFRs). The crystal structure of the dimeric FGF2-FGFR1-SOS complex at 2.6-A resolution reveals a symmetric assemblage of two 1:1:1 FGF2-FGFR1-SOS ternary complexes. Within each ternary complex SOS binds to FGF and FGFR and thereby increases FGF-FGFR affinity. SOS also interacts with the adjoining FGFR and thereby promotes protein-protein interactions that stabilize dimerization. This structural finding is supported by the inability of selectively desulfated SOS molecules to promote receptor dimerization. Thus, we propose that SOS potentiates FGF signaling by imitating the dual role of heparin in increasing FGF-FGFR affinity and promoting receptor dimerization. Hence, the dimeric FGF-FGFR-SOS structure substantiates the recently proposed "two-end" model, by which heparin induces FGF-FGFR dimerization. Moreover, the FGF-FGFR-SOS structure provides an attractive template for the development of easily synthesized SOS-related heparin agonists and antagonists that may hold therapeutic potential.
Animals↗
Enzyme kinetics and glycan structural characterization of secreted alkaline phosphatase prepared using the baculovirus expression vector system.
Secreted human alkaline phosphatase (SEAP, a model protein containing a single N-glycan chain) was expressed in Spodoptera frugiperda Sf-9 (Sf-9) and Trichoplusia ni BTI-Tn-5B1-4 (Tn-5B1-4) insect cell lines infected with recombinant Autographa californica multiple nuclear polyhedrovirus expressing SEAP under control of the polyhedrin promoter. SDS-PAGE showed that both systems expressed fairly pure rSEAP products. The rSEAP expression level was 7.0 U/mL in Tn-5B1-4, higher than the 4.1 U/mL produced by Sf-9. Kinetic analysis showed that Vmax and Km of human placental SEAP were approx 10-fold higher than that of rSEAP, whereas the Vmax and Km of rSEAP prepared using both insect cell lines were comparable. To characterize the recombinant SEAP (rSEAP) glycosylation, the purified rSEAP was digested with PNGase F to release the N-glycan chains. Glycan analysis showed the presence of oligomannose-type N-linked glycans (i.e., Man(2-8)GlcNAc2 and FucMan(3 or 4)GlcNAc2) in rSEAP from Sf9 and Tn-5B1-4 cell lines. The proportions of these oligosaccharide structures were different in the two cell lines. Man4GlcNAc2 and FucMan4GlcNAc2 were the major rSEAP N-glycans produced in Sf-9 cells, while Man2GlcNAc2 was the major rSEAP N-glycan produced in Tn-5B1-4 cells.
Alkaline Phosphatase↗