Exploiting Protein Denaturation: Albumin Hydrogels Made by Electrostatic Partial Unfolding.

摘要

The study of protein denaturation and aggregation has a tremendous potential to spur important advances in several key biomedical fronts. For example, a better understanding of the factors influencing the folding and misfolding of proteins can help us develop new approaches for the treatment of neurodegenerative diseases such as Alzheimer's, Huntington's, Parkinson's, spongiform encephalopathies and systemic amyloidoses. But knowledge we gain from these efforts will stimulate the research and development of self-assembling biomaterials for novel commercial applications.;Because of its ubiquity and clinical potential, albumin is one of the best-characterized models in protein aggregation research; yet its properties under different conditions are not fully understood. In this work, we exploited an intrinsic denaturation mechanism of albumin to fabricate a new type of albumin hydrogel. This was achieved by altering the electrostatic charges on the albumin surface leading to interdomain repulsion that exposed buried hydrophobic regions. These regions drove new quaternary assemblies that promoted hydrogel formation while preserving some of the original protein functionality within unchanged protein domains.;Using all-atom molecular dynamics simulations we showed how electrostatic forces can affect the conformation of a single albumin molecule just prior to self-assembly. The results of these simulations suggest that hydrophobic attractions and counter ion binding interactions are key to understanding the formation of this particular hydrogel. In addition, we evaluated both experimentally and computationally the residual binding affinity of the partially denatured albumin to all-trans Retinoic Acid, a cancer therapeutic with known affinity for normal albumin. This work provides critical new insights about the equilibrium conformation of albumin in its partially denatured state at low pH, and contributes significantly to our efforts to develop biocompatible protein hydrogel systems that are, driven by electrostatic partial denaturation and also exploit albumin's natural drug binding capacity.