Francesca Maccari

A 96-well assay for uronic acid carbazole reaction

Abstract A sensitive and reproducible 96-well assay of uronic acid permitting a rapid processing of a number of samples with a very low consumption of reagents is described for the determination of complex uronic acid-bearing polyanions such as hyaluronic acid, chondroitin sulfate, dermatan sulfate and heparin. The sensitivity of the reaction was approx. 1 μg for glucuronic acid and 2 μg for complex polysaccharides, with a linear function of glucuronic acid concentration between 1 and 100 μg. The relative coefficient of variations ranged from 1.5 to 8.7% for the assay performed in the 96-well plate. These values were found to be lower than those obtained by the conventional procedure.

Capillary electrophoresis of complex natural polysaccharides

Complex natural polysaccharides, glycosaminoglycans (GAGs), are a class of ubiquitous macromolecules that exhibit a wide range of biological functions and participate and regulate multiple cellular events and (patho)physiological processes. They are generally present either as free chains (hyaluronic acid and bacterial acidic polysaccharides) or as side chains of proteoglycans (PGs; chondroitin/dermatan sulfate, heparin/heparan sulfate, and keratan sulfate) and are most often found in cell membranes and in the extracellular matrix. The recent emergence of modern analytical tools for their study has produced a virtual explosion in the field of glycomics. CE, due to its high resolving power and sensitivity, has been useful in the analysis of intact GAGs and GAG‐derived oligosaccharides and disaccharides affording concentration and structural characterization data essential for understanding the biological functions of GAGs. In this review, novel off‐line and on‐line CE‐MS and MS/MS methods for screening of GAG‐derived oligosaccharides and disaccharides will be discussed.

Quantitative capillary electrophoresis determination of oversulfated chondroitin sulfate as a contaminant in heparin preparations.

A simple, accurate, and robust quantitative capillary electrophoresis (CE) method for the determination of oversulfated chondroitin sulfate (OSCS) as a contaminant in heparin (Hep) preparations is described. After degradation of the polysaccharides by acidic hydrolysis, the hexosamines produced (i.e., GlcN from Hep and GalN from OSCS) were derivatized with anthranilic acid (AA) and separated by means of CE in approximately 10 min with high sensitivity detection at 214 nm (limit of detection [LOD] of approximately 200 pg). Furthermore, AA-derivatized GlcN and GalN showed quite similar molar absorptivity, allowing direct and simple quantification of OSCS in Hep samples. Moreover, a preliminary step of specific enzymatic treatment by using chondroitin ABC lyase may be applied for the specific elimination of interference in the analysis due to the possible presence in Hep samples of natural chondroitin sulfate and dermatan sulfate impurities, making this analytical approach highly specific for OSCS contamination given that chondroitin ABC lyase is unable to act on this semisynthetic polymer. The CE method was validated for specificity, linearity, accuracy, precision, LOD, and limit of quantification (LOQ). Due to the very high sensitivity of CE, as little as 1% OSCS contaminant in Hep sample could be detected and quantified. Finally, a contaminated raw Hep sample was found to contain 38.9% OSCS, whereas a formulated contaminated Hep was calculated to have 39.7% OSCS.

Anomalous Structure of Urinary Glycosaminoglycans in Patients with Pseudoxanthoma Elasticum

BACKGROUND Pseudoxanthoma elasticum (PXE) is a hereditary connective tissue disease in which proteoglycans have altered properties. We investigated whether altered proteoglycan metabolism occurs in vivo and may be reflected in the urine of PXE individuals by analyzing the excreted polysaccharides. METHODS We measured sulfated glycosaminoglycans in the urine of 10 PXE-affected patients, 12 healthy carriers, and 20 healthy controls by agarose gel electrophoresis. Chondroitin sulfate and heparan sulfate disaccharides were also quantified by treatment with specific lyases and separation of products by chromatography. RESULTS Total polysaccharides were 34% lower in the urine of PXE-affected patients and 17% lower in healthy carriers than in the control group. Chondroitin sulfate was significantly (P <0.01) decreased, and heparan sulfate was significantly increased. The ratio of chondroitin sulfate to heparan sulfate was 2.7 for PXE-affected patients, 2.3 for healthy carriers, and 10.7 for controls. In PXE-affected individuals and carriers, chondroitin sulfate contained more 4-sulfated disaccharide, less 6-sulfated disaccharide, and decreased nonsulfated disaccharide. Heparan sulfate from PXE-affected individuals and healthy carriers produced significantly less N-sulfated disaccharide and more disaccharide sulfated at the C-6 position with no significant abnormality of the nonsulfated disaccharide percentage and sulfates:disaccharide ratio. CONCLUSIONS The urinary data support the concept that the inherited defect of the ABCC6/MRP6 transporter in PXE alters metabolism of key polysaccharides. Structural analysis of urinary sulfated polyanions may be useful in the diagnosis of PXE.

Structural characterization and antithrombin activity of dermatan sulfate purified from marine clam Scapharca inaequivalvis

Glycosaminoglycans from the body of marine clam Scapharca inaequivalvis were extracted at about 0.15- 0.18 mg/g of dry tissue, composed of dermatan sulfate (DS) (approx. 74%) and heparan sulfate (26%). After treatment with nitrous acid, DS was isolated for further complete structural characterization. Agarose-gel electrophoresis in combination with various enzymes, chondroitin ABC lyase, chondroitin B lyase, chondroitin ACII lyase from Arthrobacter aurescens, and chondroitin AC lyase from Flavobacterium heparinum, confirmed the DS nature of this polysaccharide. Furthermore, by evaluating the unsaturated disaccharides produced by the action of the various lyases, this natural polymer was found to be composed of approx. 75% of disaccharides containing iduronic acid (IdoA) mainly found in disaccharides monosulfated in position 4 of N-acetylgalactosamine (GalNAc) and disulfated in position 2 of the IdoA and 4 of GalNAc (disaccharide B typical of DS). In contrast, glucuronic acid was found to be mainly associated with the nonsulfated disaccharide (approx. 92%), while the rest formed low percentages of monosulfated disaccharides in position 4 or 6 of GalNAc preferentially located inside the chains. Generally, this GAG possesses a peculiar structure, due to the presence of significant amounts of nonsulfated disaccharide mainly located close to the nonreducing end, to the elevated percentage of the disaccharide B, and to the presence of not previously reported low amounts of the disaccharide monosulfated in position 2 of the uronic acid. S. inaequivalvis DS was also found to have a mean molecular mass of approx. 27,000 Da and a mean charge density of 1.10 that increases to 1.54 for the carbohydrate backbone composed of IdoA residues. (1)H-NMR and (13)C-NMR analyses confirmed the nature of S. inaequivalvis polymer revealed by the presence of signals related to DS corresponding to the residue of IdoA and GalNAc mainly sulfated at the C4 along with the presence of a signal belonging to the residue of H1 IdoA-2SO(4). S. inaequivalvis DS was further depolymerized by partial controlled digestion with chondroitinase ABC and separated into oligosaccharides by online HPLC/ESI-MS to obtain sequence information. The most prominent generated oligosaccharides comprised the repeating unit Delta Hex-GalNAcSO(4) thus confirming the results obtained by disaccharide analysis and the structures of the major oligosaccharides (from 6- to 10-mer) confirmed, by means of the LC-MS, the presence of approx. 20% of nonsulfated disaccharide. Furthermore, a minor but significant percentage of a monosaccharide having an m/z 300 and corresponding to GalNAcSO(4) belonging to the DS nonreducing end was observed along with saturated hexasaccharide derived from the nonreducing terminus of the intact DS ending with a uronic acid residue. Finally, S. inaequivalvis DS was calculated to possess a high heparin cofactor II activity of 169.2 +/- 10.7% fairly similar to that of several DS samples purified from porcine and bovine tissues.

Purification and characterization of hyaluronic acid from the mollusc bivalve Mytilus galloprovincialis.

Hyaluronan (hyaluronic acid, HA) was for the first time extracted, purified and characterized from the species of mollusc bivalve Mytilus galloprovincialis. HA was characterized by agarose-gel electrophoresis, 13C-NMR, HPLC and normal polarity capillary electrophoresis by evaluating the unsaturated disaccharide, DeltaDiHA (Delta-hexuronic acid-N-acetyl-glucosamine) after treatment with chondroitin ABC lyase, and by separating Delta-tetrasaccharide and Delta-hexasaccharide generated by the specific action of hyaluronate lyase from Streptomyces hyalurolyticus. The weight average molecular weight (M(w)) was found to be about 200 kDa as determined by HPSEC. HA from M. galloprovincialis was not able to interact with aggrecan from bovine cartilage to form high molecular mass aggregate and also had a very low specific viscosity, but it showed the same capacity to inhibit cell proliferation (50 microg per 10(3) human fibroblasts inhibit cell proliferation by about 50%) than high molecular mass HA. HA of M. galloprovincialis could have a physiological role in the regulation of cell functions.

Composition and structure elucidation of human milk glycosaminoglycans

To date, there is no complete structural characterization of human milk glycosaminoglycans (GAGs) available nor do any data exist on their composition in bovine milk. Total GAGs were determined on extracts from human and bovine milk. Samples were subjected to digestion with specific enzymes, treated with nitrous acid, and analyzed by agarose-gel electrophoresis and high-performance liquid chromatography for their structural characterization. Quantitative analyses yielded ∼7 times more GAGs in human milk than in bovine milk. In particular, galactosaminoglycans, chondroitin sulfate (CS) and dermatan sulfate (DS), were found to differ considerably from one type of milk to the other. In fact, hardly any DS was observed in human milk, but a low-sulfated CS having a very low charge density of 0.36 was found. On the contrary, bovine milk galactosaminoglycans were demonstrated to be composed of ∼66% DS and 34% CS for a total charge density of 0.94. Structural analysis performed by heparinases showed a prevalence of fast-moving heparin over heparan sulfate, accounting for ∼30-40% of total GAGs in both milk samples and showing lower sulfation in human (2.03) compared with bovine (2.28). Hyaluronic acid was found in minor amounts. This study offers the first full characterization of the GAGs in human milk, providing useful data to gain a better understanding of their physiological role, as well as of their fundamental contribution to the health of the newborn.

Isolation and structural characterization of chondroitin sulfate from bony fishes.

Chondroitin sulfate (CS) was purified from the bones of common fishes, monkfish, cod, spiny dogfish, salmon and tuna, and characterized in an effort to find alternative sources and new peculiar structures of this complex biomacromolecule utilized in the pharmaceutical and nutraceutical industry. Quantitative analyses yielded a CS content ranging from 0.011% for cod up to 0.34% for monkfish. The disaccharide pattern showed the presence of nonsulfated disaccharide, monosulfated species ΔDi6s and ΔDi4s, and disulfated disaccharides in different percentages. The disulfated species ΔDi2,6dis was present in all CS extracts in a range of 1.3-10.5%. The presence of these disulfated disaccharides may be a useful marker for the marine origin of CS. The newly identified sources would certainly enable the production of CS with unique disaccharide composition and properties.

Structural characterization of chondroitin sulfate from sturgeon bone

Chondroitin sulfate (CS) was purified for the first time from the bones of sturgeon and analyzed to evaluate its structure and properties. A single polysaccharide was extracted from sturgeon bone in a concentration of 0.28-0.34% for dry tissue and characterized as CS. By means of specific chondroitinases and HPLC separation of generated unsaturated repeating disaccharides, this polymer was found to be composed of approximately 55% of disaccharide monosulfated in position 6 of the GalNAc, approximately 38% of disaccharide monosulfated in position 4 of the GalNAc, and approximately 7% of nonsulfated disaccharide. The charge density was 0.93 and the ratio of 4:6 sulfated residues was equal to 0.69, a value confirmed by (13)C NMR experiments. Chondroitinase B confirmed that the purified sturgeon CS contained mainly GlcA (>99.5%) as uronic acid. PAGE analysis showed a CS having a high molecular mass with an average value of 39,880 according to HPSEC values producing a weight average molecular weight (Mw) of 37,500. On the basis of the data collected, it is reasonable to assume that CS isolated from sturgeon bone might be potentially useful for scientific and pharmacological applications, making this bony fish, which is generally discarded after ovary collection, a useful source of this polymer. Finally, this newly identified source of CS would enable the production of this macromolecule having a particular repeating disaccharide composition, structure, and biological properties.

Glycosaminoglycan Content in Term and Preterm Milk during the First Month of Lactation

Background: In a recent study, we performed a complete structural characterization of glycosaminoglycans (GAGs) in human mature milk. However, no data are available on the total content of GAGs in human milk from healthy mothers having delivered term or preterm newborns. Objectives: In this study, we evaluated the total content of GAGs in pooled milk from healthy mothers having delivered term or preterm newborns during the first month of lactation. Methods: Highly specific and sensitive analytical approaches were used to quantify human milk total GAGs. Results: Highest GAG values are present at day 4 (9.3 and 3.8 g/l in preterm and term milk, respectively), followed by a progressive decrease up to day 30 (4.3 and 0.4 g/l). The more remarkable differences are related to the first phases of lactation in which a strong decrease in GAGs was observed between days 4 and 10 (about –73% in term and –50% in preterm newborns). Conclusions: During the first month of lactation, the absolute amount of polysaccharides was constantly and significantly higher in preterm than in term milk, with a similar behavior in the decrease. These data further indicate that human milk GAGs may have an active role in protecting newborns during the first phases of lactation.