Abiotic Stimuli-Responsive Protein Affinity Reagent for IgG.

We describe an approach for the discovery of protein affinity reagents (PARs). Abiotic synthetic hydrogel copolymers can be "tuned" for selective protein capture by the type and ratios of functional monomers included in their polymerization and by the polymerization conditions (i.e., pH). By screening libraries of hydrogel nanoparticles (NPs) containing charged and hydrophobic groups against a protein target (IgG), a stimuli-responsive PAR is selected. The robust carbon backbone synthetic copolymer is rapidly synthesized in the chemistry laboratory from readily available monomers. The production of the PAR does not require living cells and is free from biological contamination. The capture and release of the protein by the copolymer NP is reversible. IgG is sequestered from human serum at pH 6.5 and following a wash step, the purified protein is released by elevating the pH to 7.3. The binding and release of the protein occur without denaturation. The abiotic material functions as a selective PAR for the F(ab')2 domain of IgG for pull-down and immunoprecipitation experiments and for isolation and purification of proteins from complex biological mixtures.

Engineering the Protein Corona of a Synthetic Polymer Nanoparticle for Broad-Spectrum Sequestration and Neutralization of Venomous Biomacromolecules.

Biochemical diversity of venom extracts often occurs within a small number of shared protein families. Developing a sequestrant capable of broad-spectrum neutralization across various protein isoforms within these protein families is a necessary step in creating broad-spectrum antivenom. Using directed synthetic evolution to optimize a nanoparticle (NP) formulation capable of sequestering and neutralizing venomous phospholipase A2 (PLA2), we demonstrate that broad-spectrum neutralization and sequestration of venomous biomacromolecules is possible via a single optimized NP formulation. Furthermore, this optimized NP showed selectivity for venomous PLA2 over abundant serum proteins, was not cytotoxic, and showed substantially long dissociation rates from PLA2. These findings suggest that it may show efficacy as an in vivo venom sequestrant and may serve as a generalized lipid-mediated toxin sequestrant.

Syntheses of sulfo-glycodendrimers using click chemistry and their biological evaluation.

A series of novel glycol-clusters containing sulfonated N-acetyl-D-glucosamine (GlcNAc) have been synthesized using click chemistry. Three dendrimers with aromatic dendrons were synthesized using chlorination, azidation and click chemistries. The resulting dendrimers were modified with azide-terminated sulfonated GlcNAc using click chemistry. The sulfonated dendrimers showed affinity for proteins, including the lectin wheat germ agglutinin and amyloid beta peptide (1-42). The dendrimers of G1 and G2 in particular showed the largest affinity for the proteins. The addition of the sulfonated GlcNAc dendrimers of G1 and G2 exhibited an inhibition effect on the aggregation of the amyloid beta peptide, reduced the b-sheet conformation, and led to a reduction in the level of nanofiber formation.

Aggregation of Alzheimer amyloid beta peptide (1-42) on the multivalent sulfonated sugar interface.

The mechanism of amyloidosis of amyloid beta (1-42) (Abeta (1-42)) was investigated by the well-defined glycocluster interface. We prepared monovalent, divalent, and trivalent 6-sulfo-N-acetyl-d-glucosamine (6S-GlcNAc) immobilized substrates. The morphology and secondary structure of Abeta (1-42) aggregates on the substrates were investigated by dynamic-mode AFM and FTIR-RAS. Abeta (1-42) interactions with multivalent sugars were evaluated by surface plasmon resonance, and the cytotoxicity of Abeta (1-42) to HeLa cells was evaluated by MTT assay. Morphological images showed, interestingly, that Abeta (1-42) aggregates had a tendency to form globules rather than fibrils as the valency of 6S-GlcNAc on the substrate was increased. The SPR measurements indicated that this morphological change of Abeta (1-42) was related to the change of binding mode, and the binding mode was dependent on the multivalency of the sugar. Globular Abeta (1-42) was more toxic than fibrillar Abeta (1-42) to HeLa cells. These results suggested that the multivalency of sugars for the amyloidosis of Abeta (1-42) was significant in its morphology and aggregation effects at the surface of the cell membrane mimic.