Biomedical subjects

R J Linhardt

Publications and source records attributed to R J Linhardt.

At least 145 records · Page 8Linked to original sources

PubMed1992

Lectin affinity electrophoresis for the separation of fluorescently labeled sugar derivatives.

Lectin affinity electrophoresis was applied to the separation of charged, fluorescent conjugates of disaccharides. Four fluorescent conjugates were prepared by reductive amination of alpha-D-Man-(1----3)-D-Man, alpha-D-Gal-(1----4)-D-Glc, alpha-D-Gal-(1----6)-D-Glc, and beta-D-Gal-(1----4)-D-Glc in the presence of 7-amino-1,3-naphthalenedisulfonic acid. These charged fluorescent-disaccharide conjugates all have identical molecular weight and in the absence of conconavalin A lectin failed to separate either by agarose or by polyacrylamide gel electrophoresis. In the presence of either free or immobilized concanavalin A, agarose gel electrophoresis and polyacrylamide gel electrophoresis could separate the fluorescent conjugate of alpha-D-Man-(1----3)-D-Man from that of alpha-D-Gal-(1----4)-D-Gal, alpha-D-Gal-(1----6)-D-Glc, and beta-D-Gal-(1----4)-D-Glc.

2-Naphthylamine↗

PubMed1991

Structural features of dermatan sulfates and their relationship to anticoagulant and antithrombotic activities.

Dermatan sulfate is a polydisperse, microheterogeneous sufated copolymer of N-acetyl-D-galactopyranose and idopyranosyluronic acid that is currently under clinical investigation as a new antithrombotic agent. The structure and activity of two pairs of dermatan sulfates, isolated from bovine and porcine mucosa, were studied. One dermatan sulfate from each species demonstrated high in vivo antithrombotic activity in the rat vena cava assay. The in vitro anticoagulant activity of each dermatan sulfate was determined using activated partial thromboplastin time (APTT), thrombin time (TT) (5 units), calcium thrombin time (CaTT) (5 units), Heptest, anti-factor Xa and anti-factor IIa antithrombin assays and heparin cofactor II amidolytic assays. The coagulation-based assays gave the best correlation to in vivo antithrombotic activity. The physical and chemical properties of each dermatan sulfate were determined using 1H-NMR and 13C-NMR spectroscopy, molecular weight determination, potentiometric titration, chemical degradative analysis, chondroitin lyase degradative analysis and oligosaccharide mapping. These analyses indicated that the major difference between dermatan sulfates from a particular species having high and low in vivo antithrombotic activity was their iduronic acid content. The relation between increased iduronic acid content and increased in vivo antithrombotic activity may be the result of the conformational flexibility of this residue.

Animals↗

PubMed1991

Determination of the pKa of glucuronic acid and the carboxy groups of heparin by 13C-nuclear-magnetic-resonance spectroscopy.

As part of our continuing studies on heparin, the present paper uses 13C-n.m.r. spectroscopy to examine the acidity of heparin's uronic acid carboxylate groups. Heparin contains three different uronic acids. In porcine mucosal heparin these account for approx. 91, 7 and 2 mol% of the total uronic acid residues. These are alpha-L-idopyranosyluronic acid 2-sulphate, beta-D-glucopyranosyluronic acid and alpha-L-idopyranosyluronic acid. The pKa values of their carboxylate groups were determined as 3.13 (using heparin), 2.79 (using heparin) and 3.0 (predicted by using model compounds) respectively. 18C-n.m.r. spectroscopy, performed at various pH values, provided a convenient method of simultaneously determining the pKa of multiple carboxylate groups, of similar acidity, within heparin D-Glucopyranosyluronic acid and heparin-derived di-, tetra- and hexa-saccharides were used as model compounds to determine pKa values of the different carboxy groups. The results suggested that molecular size had an effect on pKa. Unambiguous assignment of carboxy carbon resonances were accomplished through the use of two-dimensional n.m.r. spectroscopy. Finally, application of this method to the simplest model compound, D-glucopyranosyluronic acid, permitted the determination of the pKa of both its alpha- and beta-anomers.

Chemical Phenomena↗

PubMed1991

A new method for sequencing linear oligosaccharides on gels using charged, fluorescent conjugates.

A new method is described for sequencing linear oligosaccharides on gels using charged, fluorescent conjugates. The reducing ends of various mono-, di-, tri-, and tetra-saccharides were conjugated with monopotassium 7-amino-1,3-naphthalenedisulfonate (a fluorescent and negatively charged compound) by reductive amination using sodium cyanoborohydride. The sugar conjugates were purified by preparative gradient polyacrylamide gel electrophoresis followed by a newly developed technique involving their semi-dry transfer to positively charged nylon membranes and elution with sodium chloride. The structures of a monosaccharide- and trisaccharide-conjugate were established by f.a.b.-m.s. and 2D n.m.r. Seven linear oligosaccharide-fluorescent conjugates were treated sequentially with exoglycosidases and with endoglycosidases. Analysis of the products by gel electrophoresis provided sequence information. These methods may be useful for sequencing oligosaccharides that are chemically or enzymically (endoglycosidase) released from glycoproteins, glycolipids, and proteoglycans.

Carbohydrate Sequence↗

PubMed1991

Antithrombin III regulates complement activity in vitro.

Heparin, a polyion, exerts its main activity to inhibit coagulation through a serine protease inhibitor, antithrombin III. Previous studies have clearly shown that heparin in the absence of antithrombin III also has the capacity to regulate C activity. The present studies examined the ability of purified human antithrombin III to regulate classical and alternative pathways of C, alone and in the presence of heparin. Antithrombin III alone inhibited generation of both pathways in a dose-related manner; antithrombin III at 8 micrograms/10(7) cellular intermediates inhibited generation of the classical and alternative pathway convertases by 60 and 42%, respectively. Antithrombin III and heparin augmented each other's capacity to inhibit generation of both convertases in a dose-related manner. Antithrombin III did not appear to inhibit on the basis of charge because it is only slightly anionic (isoelectric pH value, 5.0); instead, antithrombin III may have acted as a serine protease inhibitor of the proteolytic enzymes of the C cascades. Antithrombin III acted only to inhibit formation of the alternative pathway convertase but had no activity on terminal lysis by this pathway; similarly, antithrombin III inhibited preformed EAC1,4b,2a,3b but had no activity on classical pathway cellular intermediates containing additional components. Finally, antithrombin III inhibited consumption of factor B hemolytic activity in a reaction mixture that also contained factor D and C3b, suggesting that factor D activity was also inhibited. These studies demonstrate the capacity of antithrombin III to regulate C and suggest that, in concert with heparin, antithrombin III may play an important role in the regulation of C in vivo.

Antithrombin III↗

PubMed1991

Capillary electrophoresis for the analysis of chondroitin sulfate- and dermatan sulfate-derived disaccharides.

High-voltage capillary zone electrophoresis (CZE) has been used for the first time in the analysis of non-, mono-, di-, and trisulfated disaccharides derived from chondroitin sulfate, dermatan sulfate, and hyaluronic acid. These glycosaminoglycans are first depolymerized using polysaccharide lyases. The resulting unsaturated disaccharide products can be detected by their ultraviolet absorbance at 232 nm. Different retention times were obtained for each unsaturated disaccharide analyzed by CZE. The application of a constant voltage across a 70-cm fused silica capillary using a single, simple buffer system resolved an eight-component mixture within 40 min. Quantitation of disaccharides derived from chondroitin sulfate using chondroitin ABC lyase (EC 4.2.2.4) and mixtures of unsaturated disaccharide standards was possible requiring only picogram quantities of sample. The disaccharides examined had a net charge of from -1 to -4 and were resolved primarily on the basis of net charge and secondarily on the basis of charge distribution. Two unsulfated disaccharides both containing the same unsaturated uronic acid residue were analyzed. One was from chondroitin having an N-acetylgalactosyl residue and one from hyaluronate having an N-acetylglycosyl residue. Despite the fact that they differed only by the chirality at one center, these disaccharides were resolved by CZE. CZE is a fast and simple method that represents a powerful new tool for analysis and separation of acidic disaccharide components of glycosaminoglycans.

Carbohydrate Sequence↗

PubMed1991

Capillary zone electrophoresis for the quantitation of oligosaccharides formed through the action of chitinase.

Capillary zone electrophoresis with fluorescence detection was used to analyze the products formed by chitinase acting on N-acetylchitooligosaccharide-fluorescent conjugates. Six oligosaccharides of the structure [N-acetylglucosamine(1----4)]n (where n = 1-6) were conjugated to 7-amino-1,3-naphthalene disulfonic acid by reductive amination. Each oligosaccharide-fluorescent conjugate was purified by preparative gradient polyacrylamide gel electrophoresis, semi-dry electrotransfer to a positively-charged nylon membrane and recovered by washing the membrane with salt solution. The products formed by treating each oligosaccharide-fluorescent conjugate with chitinase were analyzed by capillary zone electrophoresis. The chitinase treatment hexasaccharide-fluorescent conjugate was also examined kinetically to study the action pattern of this enzyme.

Amination↗

PubMed1991

Disaccharide compositional analysis of heparin and heparan sulfate using capillary zone electrophoresis.

Capillary zone electrophoresis (CZE) was used to separate eight commercial disaccharide standards of the structure delta UA2X(1----4)-D-GlcNY6X (where delta UA is 4-deoxy-alpha-L-threo-hex-4-enopyranosyluronic acid, GlcN is 2-deoxy-2-aminoglucopyranose, S is sulfate, Ac is acetate, X may be S, and Y is S or Ac). These eight disaccharides had been prepared from heparin, heparan sulfate, and derivatized heparins. A similar CZE method was recently reported for the analysis of eight chondroitin and dermatan sulfate disaccharides (A. Al-Hakim and R.J. Linhardt, Anal. Biochem. 195, 68-73, 1991). Two of the standard heparin/heparan sulfate disaccharides, having an identical charge of -2, delta UA2S(1----4)-D-GlcNAc and delta UA(1----4)-D-GlcNS, were not fully resolved using standard sodium borate/boric acid buffer. This buffer had proven effective in separating chondroitin/dermatan sulfate disaccharides of identical charge. Resolution of these two heparin/heparan sulfate disaccharides could be improved by extending the capillary length, preparing the buffer in 2H2O, or eliminating boric acid. Baseline resolution was achieved in sodium dodecyl sulfate in the absence of buffer. The structure and purity of each of the eight new commercial heparin/heparan sulfate disaccharide standards were confirmed using fast-atom-bombardment mass spectrometry and high-field 1H-NMR spectroscopy. Heparin and heparan sulfate were then depolymerized using heparinase (EC 4.2.2.7), heparin lyase II (EC 4.2.2.-), heparinitase (EC 4.2.2.8), and a combination of all three enzymes. CZE analysis of the products formed provided a disaccharide composition of each glycosaminoglycan. As little as 50 fmol of disaccharide could be detected by ultraviolet absorbance.

Carbohydrate Sequence↗

PubMed1991

Electrophoresis and detection of nanogram quantities of exogenous and endogenous glycosaminoglycans in biological fluids.

Glycosaminoglycans (GAGs) including chondroitin sulfate, dermatan sulfate, heparan sulfate, heparin, and keratan sulfate types I (corneal) and II (cartilage) added to buffer, plasma and urine were enzymatically depolymerized. Enzymes, including chondroitin ABC lyase (chondroitinase ABC), heparin lyase (heparinase), heparan sulfate lyase (heparitinase), endo-beta-galactosidase and keratanase were used to depolymerize each GAG. Depolymerized GAGs and GAG mixtures were fractionated using gradient polyacrylamide gel electrophoresis. Staining with alcian blue dye resulted in a distinctive and well resolved banding pattern for each GAG. When these same gels were silver stained, an increase in detection sensitivity of 1000-fold was obtained. Picogram quantities of an oligosaccharide standard in buffer could be detected with silver staining while nanogram quantities could be detected in urine or plasma. The banding pattern observed for each depolymerized GAG was well resolved from contaminants found in these biological fluids and from intact GAGs. Endogenous GAGs present in samples of human urine and plasma were first concentrated and then enzymatically depolymerized. Chondroitin or dermatan sulfates, heparan sulfate and keratan sulfate were each detected in both concentrated plasma and urine samples.

Biopolymers↗

PubMed1991

Molecular profile and mapping of dermatan sulfates from different origins.

A method for characterization and molecular profiling of acidic polysaccharides (such as dermatan sulfates) has been developed. A variety of dermatan sulfates, fractionated dermatan sulfates and low molecular weight dermatan sulfates, were examined. First, bacterial lyase-type enzymes (chondroitinase ABC) were used to depolymerize the polysaccharides. Then, mapping of these oligosaccharides (comparable to peptide mapping of proteins) was performed using gradient PAGE and SAX-HPLC. Bands and peaks observed in these maps were identified using oligosaccharide standards of defined chemical structures and physical properties. The resulting map can be used to point to structural differences among these dermatan sulfates regarding their size, charge, degree of sulfation, and contamination. Fine details of fragmentation patterns and absence or presence of contaminants were detected by silver staining of gels. These differences, particularly the content of----4)alpha-IdoA(1----3)- beta-D-GalNAc4S6S(1----sequences (detected using SAX-HPLC as delta UA(1----3)-beta-D-GalNAc4S6S) may play an important role influencing the activity of dermatan sulfates to potentiate HC II inhibition of Factor IIa.

Animals↗

PubMed1990

Immobilization of C3b with retention of functional activity.

We compared eight commercially available, pre-activated affinity chromatography supports for ability to immobilize C3b that would retain functional activity. Pre-activated supports that we studied were: cyanogen bromide activated agarose, N-hydroxysuccinimide activated agarose, Reacti-Gel HW-65, Actigel A aldehyde activated agarose, thiopropyl activated agarose, 1,4-bis(2,3-epoxypropoxy) butane activated agarose, Reacti-Gel GF-2000 and tresyl activated agarose. The amount of C3b immobilized by each support varied from 81% for Actigel A aldehyde activated agarose to only 19% for Reacti-Gel GF-2000. We examined the functional capacity of the C3b immobilized on these various supports to participate in the alternative pathway. Immobilized C3b was mixed with factors D and B of the alternative pathway and examined over time for ability to consume factor B hemolytic activity. C3b immobilized on thiopropyl activated agarose consumed factor B at a rate comparable to unbound fluid phase C3b. C3b immobilized on other supports was less active in participating in factor B consumption. Thus, we have demonstrated the ability to immobilize C3b onto a solid matrix with the immobilized C3b retaining the ability to participate in the alternative pathway. This immobilized C3b can be used to fractionate substances with high C3b binding affinity.

Animals↗

PubMed1990

Structural variation in the antithrombin III binding site region and its occurrence in heparin from different sources.

A tetrasaccharide possessing a biosynthetically permissible structural variability in and adjacent to the antithrombin III (ATIII) binding site has been isolated from heparin lyase depolymerized bovine lung heparin by using strong anion-exchange high-pressure liquid chromatography (SAX-HPLC). On the basis of two-dimensional 500-MHz 1H NMR experiments, including phase-sensitive correlated spectroscopy (COSY) and rotating frame nuclear Overhauser enhancement spectroscopy (ROESY), and fast-atom bombardment mass spectrometry (FAB-MS), the primary structure of this tetrasaccharide was unambiguously established as delta UAp2S (1----4)-alpha-D-GlcNp2S6S(1----4)-beta-D-GlcAp(1----4)-alph a-D-GlcNp2S3S6S (where delta UA represents 4-deoxy-alpha-L-threo-hex-4-enopyranosyluronic acid). The 1H NMR ROESY experiment proved to be particularly valuable in offering sequence information. Heparins from a variety of species and tissue sources were examined by oligosaccharide mapping using SAX-HPLC and gradient polyacrylamide gel electrophoresis. Two of these heparins are used as anticoagulants; they are porcine intestinal mucosal heparin and bovine lung heparin. The predominant ATIII-binding site in porcine heparin contained an N-acetylated glucosamine residue. We now report the structure of the predominant ATIII-binding site in bovine heparin as----4)-alpha-D-GlcNp2S6S(1----4)-beta-D-GlcAp(1----4)-alph a-D- GlcNp2S3S6S(1----4)-alpha-L-IdoAp2S(1----4)-alpha-D-GlcNp 2S6S(1----. This study shows the presence of one or both types of ATIII-binding-site variants in all of the heparins that were examined.

Animals↗

PubMed1990

Examination of the substrate specificity of heparin and heparan sulfate lyases.

We have examined the activities of different preparations of heparin and heparan sulfate lyases from Flavobacterium heparinum. The enzymes were incubated with oligosaccharides of known size and sequence and with complex polysaccharide substrates, and the resulting degradation products were analyzed by strong-anion-exchange high-performance liquid chromatography and by oligosaccharide mapping using gradient polyacrylamide gel electrophoresis. Heparinase (EC 4.2.2.7) purified in our laboratory and a so-called Heparinase I (Hep I) from a commercial source yielded similar oligosaccharide maps with heparin substrates and displayed specificity for di- or trisulfated disaccharides of the structure----4)-alpha-D-GlcNp2S(6R)(1----4)-alpha-L-IdoAp2S( 1----(where R = O-sulfo or OH). Oligosaccharide mapping with two different commercial preparations of heparan sulfate lyase [heparitinase (EC 4.2.2.8)] indicated close similarities in their depolymerization of heparan sulfate. Furthermore, these enzymes only degraded defined oligosaccharides at hexosaminidic linkages with glucuronic acid:----4)-alpha-D-GlcNpR(1----4)-beta-D-GlcAp(1----(where R = N-acetamido or N-sulfo). The enzymes showed activity against solitary glucuronate-containing disaccharides in otherwise highly sulfated domains including the saccharide sequence that contains the antithrombin binding region in heparin. A different commercial enzyme, Heparinase II (Hep II), displayed a broad spectrum of activity against polysaccharide and oligosaccharide substrates, but mapping data indicated that it was a separate enzyme rather than a mixture of heparinase and heparitinase/Hep III. When used in conjunction with the described separation procedures, these enzymes are powerful reagents for the structural/sequence analysis of heparin and heparan sulfate.

Carbohydrate Conformation↗

PubMed1990

Randomness in the heparin polymer: computer simulations of alternative action patterns of heparin lyase.

Heparin is a mixture of linear polysaccharides of undetermined sequence. Both biosynthetic data and computer simulation studies have established that each heparin polymer chain is comprised of oligosaccharides of defined sequence, representing ordered domains. One such ordered domian is a pentasaccharide corresponding to heparin's antithrombin III binding site. Previous computer simulation studies, performed under the assumption that heparin lyase (heparinase, EC 4.2.2.7), has a random endolytic action pattern, suggested that certain of these ordered oligosaccharide domains may themselves be nonrandomly arranged in the heparin polymer. The present work presents computer simulations of alternative action patterns for heparin lyase while assuming a random distribution of these oligosaccharide units within the heparin polymer. We consider action patterns that are determined solely by the primary structure of the substrate molecules. Results of the simulations are compared to (1) the experimental measurements of product chains formed throughout the reaction and (2) the change in weight average molecular weight Mw as a function of reaction completion as determined by absorbance at 232 nm. From the simulation of 60 action patterns for heparin lyase, we infer that one of the following statements concerning heparin and heparin lyase is true: (1) Heparin is a random arrangement of a small number of structurally defined oligosaccharide units. Heparin lyase changes its action pattern during the depolymerization of heparin (perhaps influenced by the secondary structure of substrate). (2) Heparin contain clusters of oligosaccharide sequences that are present in low concentrations (overall) in the polymer. Heparin lyase has a specificity for cleaving glycosidic linkages either exolytically at the nonreducing terminus of a chain or (endolytically) at the reducing side of these rare oligosaccharide sequence.

Carbohydrate Conformation↗

PubMed1990

Isolation and recovery of acidic oligosaccharides from polyacrylamide gels by semi-dry electrotransfer.

Acidic oligosaccharides derived from glycosaminoglycan heparin were separated by polyacrylamide gradient gel electrophoresis (PAGE). The gel could be visualized using Alcian Blue dye to give a pattern of highly resolved, well defined bands. The particular banding pattern obtained was the result of a heparinase catalyzed depolymerization which afforded oligosaccharide products that differed in size by one disaccharide unit. The separated oligosaccharides could be recovered prior to staining by electroelution onto a positively charged nylon membrane by a semi-dry transfer procedure. Subsequent elution and quantitative recovery of individual oligosaccharides from the membrane was achieved. By using multiple membrane layers a second separation dimension was obtained, resulting in increased oligosaccharide purity proportional to transfer depth. Preparative gradient polyacrylamide gel electrophoresis followed by semi-dry electro-transfer and recovery represents a novel method for the preparation of homogeneous acidic oligosaccharides.

Alcian Blue↗

PubMed1990

Structure of amiprilose hydrochloride, a novel anti-inflammatory agent.

Amiprilose hydrochloride is a carbohydrate-derived, novel anti-inflammatory with potential application in the treatment of rheumatoid arthritis. A spectroscopy-based approach was undertaken to assign both the relative and absolute configuration of its five chiral centers. The fully assigned 13C and 1H NMR spectra of amiprilose hydrochloride was used to establish the relative stereochemistry of four of its five chiral centers held rigid in its furanose ring system. Parallel synthesis of the enantiomer of amiprilose hydrochloride from L-glucose was followed by CD spectropolarimetry to establish that no inversion of chiral centers had occurred in the synthesis. The hydrobromide salt of amiprilose and its enantiomer were prepared and, together with amiprilose hydrochloride, were crystallized. X-ray crystallographic analysis resulted in the assignment of the absolute configuration of all five chiral centers.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1990

Carbohydrate analysis of glycoproteins. A review.

Many of the products prepared by biotechnological approaches, including recombinant genetic engineering, cell tissue culture, and monoclonal technologies, are glycoproteins. As little as five years ago, glycosylation was believed to play no significant role in the function of glycoproteins. Recent large scale testing of glycoprotein-based pharmaceuticals has indicated that both the extent and type of glycosylation can play a central role in glycoprotein activity. Although methods for compositional and sequence analysis of proteins and nucleic acids are generally available, similar methods have yet to be developed for carbohydrate oligomers and polymers. This review focuses on new, developing methods for the analysis and sequencing of the carbohydrate portion of glycoproteins. Included are: (1) the release of oligosaccharides and hydrolysis of carbohydrate chains using enzymatic and chemical methods; (2) fractionation by LPLC, electrophoresis, HPLC, and lectin affinity chromatography; (3) detection through the preparation of derivatives or by new electrochemical methods; (4) analysis by spectroscopic methods, including MS and high-field NMR; and (5) their sequencing through the use of multiple, well-integrated techniques. The ultimate goal of the analytical approaches discussed is to firmly establish structure and, thus, permit the study of structure-function relationships and eventually to allow the intelligent application of carbohydrate remodeling techniques in the preparation of new glycoproteins.

Carbohydrate Conformation↗

PubMed1990

Degradation of poly(ester) microspheres.

Biodegradable polymeric microspheres have been prepared by spray drying, precipitation, rotary evaporation and press grinding methods. Erosion of microspheres of poly(lactide), poly(3-hydroxybutyrate), copolymers of lactide and glycolide, and copolymers of 3-hydroxybutyrate and 3-hydroxyvalerate at 85 degrees C and 37 degrees C have been studied using ion chromatography, nuclear magnetic resonance, residual mass measurements, viscometry and gel permeation chromatography. Such studies demonstrated that these polyester matrices degraded via (1) random chain scission and (2) release of soluble monomeric and oligomeric products. Protein release from microspheres prepared by these methods indicated that most of the protein is released before the polymer matrix loses weight.

Biodegradation, Environmental↗