Amyloid-Like Aggregation in Native Protein and its Suppression in the Bio-Conjugated Counterpart

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Mukhopadhyay, A 
Stoev, ID 
King, DA 
Sharma, KP 
Eiser, E 

jats:pPrevention of protein aggregation and thus stabilization of proteins has large biological and biotechnological implications. Here we introduce Dynamic Light Scattering (DLS) and DLS-based microrheology to show how native bovine serum albumin (nBSA) forms amyloid fibrils in weakly denaturing conditions as function of time, and how stoichiometric conjugation of BSA with polymer-surfactants (PSpBSA) protects the protein form such aggregation. Employing a combination of Thioflavin-T fluorescence, Fourier transform infrared spectroscopy and other methods, we show that nBSA forms filamentous aggregates with amyloid-like structure, while PSpBSA proteins remain fully dispersed with only minor changes in their folding state, even when continuously heated for up to 5 days in denaturation conditions at 65 °C. Time-resolved DLS-based microrheology studies demonstrate that suspensions of the filamentous nBSA aggregates become viscoelastic for concentrations ≥200 jats:italicμ</jats:italic>M. Our results indicate that after 6 days in aggregation conditions, the elastic modulus jats:italicG</jats:italic>′(jats:italicω</jats:italic>) of nBSA solutions went from zero initially to values of up to 3.6 Pa, indicating that the filaments become long enough to form an entangled, viscoelastic network. Interestingly, heating 200 jats:italicμ</jats:italic>M native BSA solutions at 65 °C for 2 days in Eppendorf tubes resulted in self-standing films rather than dispersed filaments. These films exhibited strong ThT-fluorescence intensities and a predominant jats:italicβ</jats:italic>-sheet secondary structure in FTIR studies, suggesting that the self-standing microstructure of the film resulted from hierarchical self-assembly of the amyloid fibrils.</jats:p>

protein aggregation, nBSA, amyloid fibrils, bio-conjugated protein, dynamic light scattering, microrheology, stability against denaturation
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Frontiers in Physics
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Frontiers Media SA