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Inhibiting amyloid-like aggregation through bio-conjugation of proteins with polymer surfactant

Prevention of protein aggregation and thus stabilization of proteins has large biological and biotechnological implications. Here, we show that inhibition of amyloid-like aggregates is possible in stoichiometric conjugates of polymer surfactant and bovine serum albumin (BSA) chosen as a model protein. We investigate using a combination of Thioflavin-T fluorescence spectroscopy, dynamic light scattering and FTIR spectroscopy the aggregation behavior in polymer surfactant modified and unmodified (native) BSA solutions. The BSA-polymer surfactant conjugates are stable up to 5 days under aggregation conditions, while native BSA forms amyloid fibrillar structures. Further, DLS-based micro-rheology studies performed with heat-treated 100 to 200 μM native BSA aggregates provided understanding of the equilibrium elastic and viscous moduli over a very large frequency range, reaching MHz, which are inaccessible using bulk rheology. Our results indicate that after 6 days of aggregation conditions, elastic moduli showed values between 1.2 to 3.6 Pa corresponding to an entanglement length (ξ) of 105 nm. Interestingly, heating 200 μM native BSA solution at 65 degree C for 2 days in a plastic Eppendorf resulted in self-standing films. These films exhibited strong ThT-fluorescence intensity and a predominant \b{eta}-sheet secondary structure from the FTIR studies, suggesting that self-standing microstructure resulted from hierarchical self-assembly of amyloid fibrils.