Chemistry of Nucleic Acids by Harri Lönnberg

Chemistry of Nucleic Acids by Harri Lönnberg

Author:Harri Lönnberg
Language: eng
Format: epub
Publisher: De Gruyter
Published: 2020-07-05T17:25:05.545000+00:00


6.7

Glycocluster conjugates

Branched linkers are required for targeting therapeutic oligonucleotides to sugar binding proteins, lectins, on cell surface. Lectins contain several binding sites for sugar monomers and they show marked enhancement in affinity per mole of sugar compared to the corresponding monovalent ligand. The phenomenon is known as glycocluster effect. In other words, the lack of strength of an individual interaction is compensated by multivalency. To ensure high affinity binding, several sugars should be attached to a common scaffold that allows simultaneous binding of all sugar ligands to the subunits of lectin. A well-known example is an asialoglycoprotein receptor in hepatocytes that requires simultaneous binding of three N-acetylgalactosamine ligands for high affinity interaction [62] (cf. Section 11.3). A triantennary conjugate attached to the 5′-terminus of oligonucleotide has been shown to warrant efficient recognition of the receptor and internalization of the oligonucleotide [63]. The conjugate has been prepared by an active ester method in solution; a pentafluorophenyl ester of a triantennary construct of three fully acetylated N-acetylgalactosmines is reacted with a 5′-aminohexyl oligonucleotide and then subjected to ammonolytic deprotection of the sugar ligands (Figure 6.8A).



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