Glycoprotein Mimics with Tunable Functionalization through Global Amino Acid Substitution and Copper Click Chemistry

Glycoproteins and their mimics are challenging to produce because of their large number of polysaccharide side chains that form a densely grafted protein-polysaccharide brush architecture. Herein a new approach to protein bioconjugate synthesis is demonstrated that can approach the functionalization densities of natural glycoproteins through oligosaccharide grafting. Global amino acid substitution is used to replace the methionine residues in a methionine-enriched elastin-like polypeptide with homopropargylglycine (HPG); the substitution was found to replace 93% of the 41 methionines in the protein sequence as well as broaden and increase the thermoresponsive transition. A series of saccharides were conjugated to the recombinant protein backbones through copper(I)-catalyzed alkyne-azide cycloaddition to determine reactivity trends, with 83-100% glycosylation of HPGs. Only an acetyl-protected sialyllactose moiety showed a lower level of 42% HPG glycosylation that is attributed to steric hindrance. The recombinant glycoproteins reproduced the key biofunctional properties of their natural counterparts such as viral inhibition and lectin binding.

Antiviral Agents from Multivalent Presentation of Sialyl Oligosaccharides on Brush Polymers

Bioinspired brush polymers containing α-2,6-linked sialic acids at the side chain termini were synthesized by protection-group-free, ring-opening metathesis polymerization. Polymers showed strain-selective antiviral activity through multivalent presentation of the sialosides. The multivalent effect was further controlled by independently varying the degree of polymerization, the number density of sialic acids, and the length of side chains in the brush polymers. Optimizing the three-dimensional sialoside spacing for better binding to hemagglutinin trimers was of critical importance to enhance the multivalent effect and the antiviral activity determined by hemagglutination inhibition assays and in vitro infection assays. By taking advantage of their structural similarities with native mucins, these brush polymers can be used as model systems to dissect the intricate design principles in natural mucins.

2,6-Diacylnaphthalene-1,8:4,5-bis(dicarboximides): synthesis, reduction potentials, and core extension

2,6-Diacyl derivatives of naphthalene-1,8:4,5-bis(dicarboximide)s have been synthesized via Stille coupling reactions of the corresponding 2,6-distannyl derivative with acyl halides. Reaction of these diketones with hydrazine gave phthalazino[6,7,8,1-lmna]pyridazino[5,4,3-gh][3,8]phenanthroline-5,11(4H,10H)-dione fused-ring derivatives. The products were characterized by UV-vis absorption spectroscopy and electrochemistry, modeled using density functional theory calculations, and, in some cases, studied and compared using single-crystal X-ray diffraction.