Explore by Category: Alpha-Gal | LacNAc (Poly-LacNAc) | Blood Groups | N-linked Glycans | O-linked Glycans | Sialosides | Glycosaminoglycans

Common Glycan Structures

Glycans exhibit enormous structural diversity, however, among this complexity there are structures which share common monosaccharide sequence and linkage patterns. These common glycan structures include various terminal epitopes, linear extensions, and core structures such as those found on N- and O-linked glycoproteins, glycolipids, and glycosaminoglycans. The diversity of glycan structures allows them to serve as important markers for various biological processes, including pathogen recognition, cell signaling, and immune regulation.

We have an extensive portfolio of glycan products representing the diversity of these common glycan structures.

Alpha-Gal

The alpha-galactose (alpha-Gal) epitope is a disaccharide unit composed of a galactose-alpha-1,3-galactose sequence. It is a naturally abundant structure found on glycolipids and glycoproteins on the cell surface of non-primate mammals. Notably, humans and higher primates do not express the alpha-gal epitope because they lack the functional alpha-1,3-galactosyltransferase required to synthesize the glycan.

Humans can develop IgE antibodies against alpha-Gal epitopes following repeated exposure, primarily through bites from lone star ticks (Amblyomma americanum), which inject alpha-Gal into the bloodstream during feeding. Sensitization to alpha-Gal can lead to alpha-Gal syndrome, characterized by a delayed allergic reaction several hours after consuming mammalian meat or mammalian-derived products. Alpha-Gal syndrome presents challenges in healthcare settings, affecting dietary choices, medical treatments such as pharmaceuticals derived from mammalian sources, and even xenotransplantation. Ongoing research focuses on understanding the mechanisms of alpha-Gal sensitization, the role of tick bites, and potential treatment or desensitization strategies.

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LacNAc (Poly-LacNAc)

Type-II N-acetyllactosamine or LacNAc is a disaccharide structure consisting of galactose (Gal) β1,4-linked to N-acetylglucosamine (GlcNAc). Poly-LacNAc structures are characterized by repeating LacNAc units linked together in a linear fashion – (Galβ1-4GlcNAcβ1-)n3Galβ1-4GlcNAc. LacNAc and poly-LacNAc are common extensions found on oligosaccharide chains attached to N- and O-linked glycoproteins, and glycolipids. LacNAc units also serve as scaffolds for other modifications including sialylation, fucosylation, and sulfation. LacNAc chains are ligands for glycan binding proteins, such as galectins.

We provide a variety of LacNAc extended structures including linear, N-linked, and O-linked glycans. These products can be modified at the reducing end with a range of linkers for coupling or immobilization.

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Blood Groups

The blood group glycans are specific structures that are covalently attached to glycoproteins and glycolipids on the surface of red blood cells (RBCs) and other cells. They are also found on secreted glycoproteins. These glycans are terminal structures and serve as antigens that define an individual’s blood group phenotype. The blood groups can be recognized as foreign antigens by antibodies; therefore, it is crucial to match donor and recipient phenotypes for blood transfusions and organ transplantations to prevent adverse immune reactions.

The ABO blood group system (A, B, AB, and O-type) is one of the most important and well-known systems for classifying human blood. It is based on the presence or absence of specific glycan structures. Individuals with blood type A express the trisaccharide GalNAcα1-3(Fucα1-2)Gal whereas blood type B individuals express Galα1-3(Fucα1-2)Gal. Individuals with blood type AB express both the A and B antigens. Blood type O is defined by the core disaccharide Fucα1-2Gal which lacks the α1,3-linked GalNAc or Gal residues. Individuals with blood type O are considered universal donors because their blood can be given to individuals with A or B without risk of an immune response.

The Lewis blood group system (LeX, LeA, LeY, and LeB) is another important classification of blood group antigens. The Lewis antigen glycans are also found on glycolipids and glycoproteins expressed on the surface of RBCs and in body fluids. The Lewis glycans are:

Lewis X - Galβ1-4(Fucα1-3)GlcNAc

Lewis Y - Fucα1-2 Galβ1-4(Fucα1-3)GlcNAc

Lewis A - Galβ1-3(Fucα1-4)GlcNAc

Lewis B - Fucα1-2 Galβ1-3(Fucα1-4)GlcNAc

We provide synthetic ABO and Lewis blood group glycans equipped with a variety of linkers including for example amine, azide and alkyne, biotin, NHS-activated esters, and lipid or PEGylated lipid.

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N-linked Glycans

N-linked glycosylation is a crucial post-translational modification playing essential roles in protein folding, stability, trafficking, and function. N-linked glycans are covalently attached to proteins at specific asparagine (Asn) residues by an N-glycosidic bond. In eukaryotes, N-linked glycans are attached to the protein via a chitobiose (GlcNAc2) β-linked to Asn and are constructed of a common biantennary core pentasaccharide (Man3GlcNAc2). Biosynthesis of N-linked glycans begins in the endoplasmic reticulum (ER), where an oligosaccharide precursor (Glc3Man9GlcNAc2) is enzymatically assembled on a lipid carrier (dolichol phosphate). The precursor is then transferred from dolichol phosphate to Asn residues within the Asn-X-Ser/Thr (where X cannot be proline) motif of the nascent polypeptide chain during protein translation. After transfer, the glycan undergoes extensive processing in the ER and Golgi, where specific glycosidases and glycosyltransferases trim and modify the glycan structure to its mature form.

The three main classes of N-linked glycans, include (i) high mannose type such as Man9GlcNAc2, (ii) complex type where the terminal mannose residues of the core pentasaccharide are modified with LacNAc. The LacNAc branches can be extended and modified with other glycans such as sialic acid and fucose, (iii) hybrid type N-linked glycans have multiple mannose residues on one of the terminal mannose residues of the core pentasaccharide while the other mannose residue is modified with LacNAc.

We provide a variety of N-linked glycans. These include high mannose types such as Man9GlcNAc2-Asn and Man5GlcNAc2-Asn as well as the core pentasaccharide. We have a portfolio of complex type N-linked glycans including biantennary, poly-LacNAc extended and sialylated structures. These N-linked glycans can be modified with a variety of linkers for immobilization or conjugation.

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O-linked Glycans

Many glycoproteins carry O-GalNAc (N-acetylgalactosamine) linked glycans attached to the hydroxyl group of serine (Ser) or threonine (Thr) residues. This post-translational modification is common among glycoproteins, but this modification is prevalent in mucin type glycoproteins which have long sequences containing multiple O-GalNAc glycans. The biosynthesis of O-linked glycans is initiated by the addition of GalNAc in an α-linkage to Ser or Thr by a polypeptide GalNAc-transferase forming the structure GalNAcα1-Ser/Thr, also known as the Tn-antigen. The initial GalNAc can be elongated enzymatically to form the core O-linked glycan structures. These include:

Core-1 - Galβ1-3GalNAcα-Ser/Thr (also known as the Tf-antigen (Thomsen-Friedenreich antigen) or T-antigen).

Core-2 - Galβ1-3(Galβ1-6)GalNAcα-Ser/Thr

Core-3 - GalNAcβ1-3GalNAcα-Ser/Thr

Core-4 - GalNAcβ1-3(GalNAcβ1-6)GalNAcα-Ser/Thr

The core structures can be further enzymatically modified by the addition of sialylation, fucosylation, and LacNAc units.

We provide a variety of O-GalNAc linked glycans. These include the Tn antigen and the Core structures (1-4). These structures include sialylated, fucosylated, and LacNAc extended O-linked glycans. The products can be modified with a variety of linkers for conjugation and immobilization.

  • Sialyl Tn

    Sialyl Tn

    Sialyl Tn (Neu5Acα2-6GalNAc) antigen is an O-GalNAc linked glycan. STn antigen expression...

    Sialyl Tn

  • Core-1

    Core-1

    Core-1 (Galβ1-3GalNAc) is an O-GalNAc linked glycan. This probe can be used...

    Core-1

  • Core-2

    Core-2

    The Core-2 trisaccharide, Galβ1-3(GlcNAcβ1-6)GalNAc, is one of the common O-linked glycan cores....

    Core-2

  • Core-3

    Core-3

    The Core-3 disaccharide, GlcNAcβ1-3GalNAc, is one of the common O-linked glycan cores....

    Core-3

  • Core-4

    Core-4

    The Core-4 trisaccharide, GlcNAcβ1-3(GlcNAcβ1-6)GalNAc, is one of the common O-linked glycan cores....

    Core-4

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Sialosides

Sialosides, also known as sialylated glycoconjugates or sialoglycans, are a diverse group of glycoconjugates that contain sialic acid residues. Sialic acids are a family of nine-carbon acidic sugars, including N-acetyl neuraminic acid (Neu5Ac) and N-glycolyl neuraminic acid (Neu5Gc). Sialic acids are linked via glycosidic bonds (α2-3, α2-6, and α2-8) to terminal positions of glycans attached to glycoproteins and glycolipids on the cell surface and secreted proteins. These molecules are ligands for different glycan binding proteins including the Siglecs, Selectins, and influenza hemagglutinin. They play crucial roles in various biological processes including cell-cell interaction, glycoprotein stability, and immune modulation. Dysregulation of sialic acid expression including aberrant sialylation is associated with various diseases including cancer, inflammatory diseases, and neurodegenerative disorders.

We have a wide portfolio of sialylated glycans including terminal epitopes such as sialylated LacNAc, and sialosides of N- and O-linked glycans. These sialosides can be modified with a variety of linkers for conjugation or immobilization and can be used to screen glycan binding proteins such as the Siglecs or influenza hemagglutinin. Focused libraries of sialoside ligands can also be provided.

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Glycosaminoglycans

Glycosaminoglycans (GAGs) are a diverse group of linear glycans composed of repeating disaccharide units. The disaccharide consists of an amino sugar such as glucosamine (GlcN) (that is N-acetylated (GlcNAc) or N-sulfated (GlcNS)) or N-acetylgalactosamine (GalNAc) and a uronic acid such as glucuronic acid (GlcA) or iduronic acid (IdoA), or galactose (Gal). GAGs are an essential component of the extracellular matrix and connective tissues, where they play critical roles in maintaining tissue hydration, elasticity, and structural integrity. GAGs are classified into several distinct families based on their disaccharide composition and sulfation patterns:

Hyaluronan – Unlike other GAGs, hyaluronan is non-sulfated and has a simple disaccharide structure consisting of glucuronic acid and N-acetylglucosamine. Hyaluronan does not occur covalently linked to a protein core. It is a major component of synovial fluid, vitreous humor, and connective tissues, contributing to tissue hydration and lubrication.

Chondroitin Sulfate – Composed of repeating disaccharide units of glucuronic acid and N-acetylgalactosamine, which can be sulfated at various positions. They are predominantly found in cartilage, bone, and skin, where they provide mechanical support and resilience.

Dermatan Sulfate – Characterized by repeating disaccharide units of iduronic acid and N-acetylgalactosamine, this GAG is found in skin, tendons, and heart valves. It plays a role in wound healing and tissue repair.

Heparin and Heparan Sulfate – These GAGs have repeating disaccharide units of glucuronic acid (or iduronic acid) and glucosamine. Heparin is known for its potent anticoagulant properties, while heparan sulfate is involved in cell signaling and growth factor regulation.

Keratan Sulfate – Composed of sulfated repeating disaccharide units of galactose and N-acetylglucosamine (poly-N-acetyllactosamine). Keratan sulfate is primarily found in the cornea, cartilage, and bone, where it contributes to tissue transparency and strength.

GAGs are crucial for many physiological processes, and abnormalities in their metabolism or function can lead to a range of diseases. For example, mucopolysaccharidoses (MPS) are a group of inherited lysosomal storage diseases (LSDs) caused by deficiencies in specific enzymes responsible for the degradation of GAGs. This leads to the accumulation of GAGs in lysosomes and other tissues. MPS diseases are classified based on the specific enzyme deficiency and the type of GAGs that accumulate.

We have a wide portfolio of synthetic, well-defined, and highly pure GAG disaccharide and tetrasaccharide structures including reducing sugars. These compounds can be used as authentic samples or diagnostic standards for degradation products in projects developing therapeutics for GAG related lysosomal storage diseases. Focused libraries of GAG structures can also be provided.

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