Synthesis and Aggregation of Polymer-Amyloid β Conjugates

Modulating the assembly of medically relevant peptides and proteins via macromolecular engineering is an important step in modifying their overall pathological effects. The synthesis of polymer-peptide conjugates composed of the amyloidogenic Alzheimer peptide, Aβ_1-40 , and poly(oligo(ethylene glycol)_m acrylates) (m = 2,3) with different molecular weights (M_n = 1400-6600 g mol^-1 ) is presented here. The challenging conjugation of a synthetic polymer to an in situ aggregating protein is established via two different coupling strategies, only successful for polymers with molecular weights not exceeding 6600 g mol^-1 , relying on resin-based synthesis or solution-based coupling chemistries. The conjugates are characterized by high-performance liquid chromatography and matrix-assisted laser desorption ionization time-of-flight mass spectrometry. The aggregation of these polymer-Aβ_1-40 conjugates, as monitored via thioflavine-T (ThT)-fluorescence spectroscopy, is accelerated mainly upon attaching the polymers. However, the appearance of the observed fibrils is different from those composed of native Aβ_1-40, specifically with respect to length and morphology of the obtained aggregates. Instead of long, unbranched fibrils characteristic for Aβ_1-40 , bundles of short aggregates are observed for the conjugates. Finally, the ThT kinetics and morphologies of Aβ_1-40 fibrils formed in the presence of the conjugates give some mechanistic insights.