Synthesis of mono-, di- and tri-O-sulfated N-acetyllactosamines in a form suitable for glycochip printing

Specificity of viscumin revised. As probed with a printed glycan array

Viscumin, a lectin used in anti-cancer therapy, was originally considered as βGal recognizing protein; later, an ability to bind 6'-sialyl N-acetyllactosamine (6'SLN) terminated gangliosides was found. Here we probed viscumin with a printed glycan array (PGA) containing a large number of mammalian sulfated glycans, and found a strong binding to glycans with 6-O-SuGal moiety as lactose, N-acetyllactosamine (LN), di-N-acetyllactosamine (LacdiNAc), and even 6-O-SuGalNAcα (but not SiaTn). Also, the ability to bind some of αGal terminated glycans, including Galα1-3Galβ1-4GlcNAc, was observed. Unexpectedly, only weak interaction was detected with parent neutral β-galactosides including LN-LN-LN and branched (LN)₂LN oligolactosamines; in the light of these data, one should not confidently classify viscumin as a β-galactoside-binding lectin. Carrying out PGA in the presence of neutral or sulfated/sialylated glycan, together with sequential elution from lactose-sepharose and consideration of the protein structure, lead to the conclusion that two glycan-binding sites of viscumin have different specificities, one of which prefers charged sulfated and sialylated moieties.

Synthesis of 13 C-labelled sulfated N-acetyl-d-lactosamines to aid in the diagnosis of mucopolysaccharidosis diseases

Morquio A syndrome is an autosomal mucopolysaccharide storage disorder that leads to accumulation of keratan sulfate. Diagnosis of this disease can be aided by measuring the levels of keratan sulfate in the urine. This requires the liquid chromatography tandem mass spectrometry (LCMS/MS) measurement of sulfated N-acetyl-d-lactosamines in the urine after cleavage of the keratan sulfate with keratanase II. Quantification requires isotopically-labelled internal standards. The synthesis of these ¹³ C₆ -labelled standards from ¹³ C₆ -galactose and N-acetylglucosamine is described. The required protected disaccharide is prepared utilising a regioselective, high yielding β-galactosylation of a partially protected glucosamine acceptor and an inverse addition protocol. Subsequent synthesis of the ¹³ C₆ -labelled mono and disulfated N-acetyllactosamines was achieved in five and eight steps, respectively, from this intermediate to provide internal standards for the LCMS/MS quantification of keratan sulfate in urine.

Structural studies of the interaction of Crataeva tapia bark protein with heparin and other glycosaminoglycans

CrataBL, a protein isolated from Crataeva tapia bark, which is both a serine protease inhibitor and a lectin, has been previously shown to exhibit a number of interesting biological properties, including anti-inflammatory, analgesic, antitumor, and insecticidal activities. Using a glycan array, we have now shown that only sulfated carbohydrates are effectively bound by CrataBL. Because this protein was recently shown to delay clot formation by impairing the intrinsic pathway of the coagulation cascade, we considered that its natural ligand might be heparin. Heparin is a glycosaminoglycan (GAG) that interacts with a number of proteins, including thrombin and antithrombin III, which have a critical, essential pharmacological role in regulating blood coagulation. We have thus employed surface plasmon resonance to improve our understanding of the binding interaction between the heparin polysaccharide and CrataBL. Kinetic analysis shows that CrataBL displays strong heparin binding affinity (KD = 49 nM). Competition studies using different size heparin-derived oligosaccharides showed that the binding of CrataBL to heparin is chain length-dependent. Full chain heparin with 40 saccharides or large oligosaccharides, having 16-18 saccharide residues, show strong binding affinity for CrataBL. Heparin-derived disaccharides through tetradecasaccharides show considerably lower binding affinity. Other highly sulfated GAGs, including chondroitin sulfate E and dermatan 4,6-disulfate, showed CrataBL binding affinity comparable to that of heparin. Less highly sulfated GAGs, heparan sulfate, chondroitin sulfate A and C, and dermatan sulfate displayed modest binding affinity as did chondroitin sulfate D. Studies using chemically modified heparin show that N-sulfo and 6-O-sulfo groups on heparin are essential for CrataBL-heparin interaction.

Both influenza hemagglutinin and polymerase acidic genes are important for delayed pandemic 2009 H1N1 virus clearance in the ferret model

We previously showed that a pandemic virus, A/Tennessee/560/09(H1N1), had the potential to adapt to human bronchial epithelial cells by the acquisition of hemagglutinin (HA) K154Q and polymerase acidic (PA) protein L295P mutations that conferred a more virulent phenotype. To better elucidate the role of each mutations, we generated recombinant viruses carrying single mutations or both mutations concurrently. The replication of all mutant viruses was significantly higher than that of the wild-type A/Tennessee/560/09 virus in human cells. The HA K154Q mutation reduced the receptor binding affinity of A/Tennessee/560/09 virus to 6-Su-6'SLN and biantennary 6'SLN receptors. In ferrets, H1N1 virus with HA K154Q and PA L295P mutations exhibited significantly higher titers in the upper respiratory tract compared to all other viruses 6 days post-infection. Our results suggest that both single mutations HA K154Q and PA L295P are necessary for delayed virus clearance of A/Tennessee/560/09(H1N1) influenza virus in a ferret animal model.

Chemical synthesis of 6(GlcNAc)- and 6(Gal)-O-sulfated SiaLe(X) tetrasaccharides in spacer-armed form

Practical synthesis of tetrasaccharide sulfates, 6((GlcNAc))-O-Su-SiaLe(X)-OCH(2)CH(2)CH(2)NH(2) and 6((Gal))-O-Su-SiaLe(X)-OCH(2)CH(2)CH(2)NH(2) (Su( )SO(3)H), selectin ligands, and leu- kocyte trafficking agents is presented. Both sulfates were synthesized starting from the same precursor, protected SiaLe(x), by the conventional procedures of carbohydrate chemistry. The sulfated SiaLe(x) derivative was modified at the spacer group to give 6((Gal))-O-Su-SiaLe(x)- OCH(2)CH(2)CH(2)NH-COCH(2)CH(2)C[triple bond]CH, convenient for "click chemistry" mode conjugation with an azido carrier, particularly, for the synthesis of an immunogen.