In Situ Analysis of Weakly Bound Proteins Reveals Molecular Basis of Soft Corona Formation

Abstract

Few experimental techniques allow the analysis of the protein corona in situ. As a result, little is known on the effects of nanoparticles on weakly bound proteins that form the soft corona. Despite its biological importance, our understanding of the molecular bases driving its formation is limited. Here we show that hemoglobin can form either a hard or a soft corona on silica nanoparticles depending on the pH conditions. Using cryoTEM and synchrotron-radiation circular dichroism, we show that nanoparticles alter the structure and the stability of weakly bound proteins in situ. Molecular dynamics simulation identified the structural elements driving protein-nanoparticle interaction. Based on thermodynamic analysis, we show that nanoparticles stabilize partially unfolded protein conformations by enthalpy-driven molecular interactions. We suggest that nanoparticles alter weakly bound proteins by shifting the equilibrium towards the unfolded states at physiological temperature. We show that the classical approach based on nanoparticle separation from the biological medium fails to detect destabilization of weakly bound proteins, and therefore cannot be used to fully predict the biological effects of nanomaterials in situ.

Hard and Soft Protein Corona of Nanomaterials: Analysis and Relevance

“…In addition, they reported the antifouling properties of a zwitterionicfunctionalized NP, where only an SC was formed. Another in situ analysis was performed by Sanchez-Guzman et al [129], where they aimed to reveal the molecular basis of SC formation. In their investigation, the authors investigated the PC formed by hemoglobin on SiNPs.…”

In vivo Protein Corona Formation: Characterizations, Effects on Engineered Nanoparticles’ Biobehaviors, and Applications

“…In recent, in situ techniques were employed to character soft corona. For example, a new method using cryoTEM and synchrotron-radiation CD was developed to analyze the weakly bound proteins and reveal molecular basis of soft corona in situ (Sanchez-Guzman et al, 2020). Soft corona proteins were altered by ENPs based on shifting the equilibrium toward the unfolded states at physiological temperature.…”

The Protein Corona Leads to Deformation of Spherical Micelles

“…At this point ac ritical discussion is necessary to evaluate the meaning of these results.Afew studies have shown that the protein corona may not change the shape of nanoparticles after protein absorption. This has been demonstrated using liposomes, [34] silica particles [35] and polystyrene particles. [36] However,t hese nanoparticles are either hard and therefore unlikely to deform, or they do not have ahairy surface where proteins may entangle.I ti st herefore reasonable to believe that hairy and soft nanoparticles may indeed undergo ashape change triggered by the tension in the shell.…”