Abstract
Biomacromolecule activity is usually related to its ability to keep a specific structure. However, in solution, many parameters (pH, ionic strength) and external compounds (polyelectrolytes, nanoparticles) can modify biomacromolecule structure as well as acid/base properties, thus resulting in a loss of activity and denaturation. In this paper, the impact of neutral and charged nanoparticles (NPs) is investigated by Monte Carlo simulations on polypeptide (PP) chains with primary structure based on bovine serum albumin. The influence of pH, salt valency, and NP surface charge density is systematically studied. It is found that the PP is extended at extreme pH, when no complex formation is observed, and folded at physiological pH. PP adsorption around oppositely-charged NPs strongly limits chain structural changes and modifies its acid/base properties. At physiological pH, the complex formation occurs only with positively-charged NPs. The presence of salts, in particular those with trivalent cations, introduces additional electrostatic interactions, resulting in a mitigation of the impact of negative NPs. Thus, the corona structure is less dense with locally-desorbed segments. On the contrary, very limited impact of salt cation valency is observed when NPs are positive, due to the absence of competitive effects between multivalent cations and NP.
Highlights
Serum albumins, the most abundant plasma proteins in the mammalian circulatory system synthesized in the liver, have been a subject of interest for many years
We propose here an original model to systematically follow the evolution of PP conformational and acid/base properties in presence of NPs, counterions, and salt
The PP chain is considered adsorbed if at least one amino acids (AAs) center is situated within the AdsL layer for more than 50% of the Monte Carlo (MC) steps during the production period
Summary
The most abundant plasma proteins in the mammalian circulatory system synthesized in the liver, have been a subject of interest for many years. Other short-range interactions, such as van der Waals, hydrophobic, hydrophilic, and structural, play a role in the formation of complexes [21] In this context, serum albumin proteins can be found destabilized with silver NPs but stable with gold NPs, which can be used to stop HSA unfolding by ultraviolet radiation [22,23]. Salt screening effects modify long-range interactions between proteins and NPs, and impact protein–protein repulsions, which can result in a more efficient fibrillation process of serum albumins [28,29]. [39], the model was extended to investigate the effect of chain hydrophobicity and charge distribution in the interaction processes with NPs. Intermediate and hydrophilic backbones were found extended at extreme pH and folded at physiological pH. The PP chain is considered adsorbed if at least one AA center is situated within the AdsL layer for more than 50% of the MC steps during the production period
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