Modulating protein unfolding and refolding via the synergistic association of an anionic and a nonionic surfactant
Key Takeaways
This paper explores the complex interactions between proteins and surfactants. Through careful titration, the authors reveal how proteins undergo unfolding and refolding at varying ratios of ionic and nonionic surfactants, uncovering unexpected behaviors along the way. A deeper understanding of this interplay is essential for applications that rely on surfactants to stabilize proteins, including drug formulation, biotechnology, and beyond.
Abstract
Hypothesis
Nonionic surfactants can counter the deleterious effect that anionic surfactants have on proteins, where the folded states are retrieved from a previously unfolded state. However, further studies are required to refine our understanding of the underlying mechanism of the refolding process. While interactions between nonionic surfactants and tightly folded proteins are not anticipated, we hypothesized that intermediate stages of surfactant-induced unfolding could define new interaction mechanisms by which nonionic surfactants can further alter protein conformation.
Experiments
In this work, the behavior of three model proteins (human growth hormone, bovine serum albumin, and β-lactoglobulin) was investigated in the presence of the anionic surfactant sodium dodecylsulfate, the nonionic surfactant β-dodecylmaltoside, and mixtures of both surfactants. The transitions occurring to the proteins were determined using intrinsic fluorescence spectroscopy and far-UV circular dichroism. Based on these results, we developed a detailed interaction model for human growth hormone. Using nuclear magnetic resonance and contrast-variation small-angle neutron scattering, we studied the amino acid environment and the conformational state of the protein.
Findings
The results demonstrate the key role of surfactant cooperation in defining the conformational state of the proteins, which can shift away or toward the folded state depending on the nonionic-to-ionic surfactant ratio. Dodecylmaltoside, initially a non-interacting surfactant, can unexpectedly associate with sodium dodecylsulfate-unfolded proteins to further impact their conformation at low nonionic-to-ionic surfactant ratio. When this ratio increases, the protein begins to retrieve the folded state. However, the native conformation cannot be fully recovered due to remnant surfactant molecules still adsorbed to the protein. This study demonstrates that the conformational landscape of the protein depends on a delicate interplay between the surfactants, ultimately controlled by the ratio between them, resulting in unpredictable changes in the protein conformation.
Other Publications Featuring Labbot
Insulin Amyloid Morphology is Encoded in H-bonds and Electrostatics Interactions Ruling Protein Phase Separation
This article investigates how hydrogen bonds and electrostatic interactions between ions and proteins influence phase separation and amyloid formation. Using a combination of microscopy, small-angle X-ray scattering, and ThT fluorescence, the authors map out how different ions on the Hofmeister scale alter the aggregation landscape.
Disassembly and in vitro cell compatibility of α-lactalbumin particulates under physiologically relevant conditions
The study showcases excellent techniques and controls for accurately measuring conditions inside droplets. Additionally, it offers insights into molecular tools for fine-tuning the critical concentration of synthetic condensates and modulating the partitioning of small molecules within them.
Oxygen Partitioning into Biomolecular Condensates is Governed by Excluded Volume
In this paper, the authors demonstrate that molecular oxygen is selectively excluded from protein condensates. Investigating the underlying driving forces reveals that this partitioning is driven by excluded volume effects rather than hydrophobicity.