A minimal length rigid helical peptide motif allows rational design of modular surfactants

Sudipta Mondal,Linda J.W Shimon,Lihi Adler-Abramovich,Daniel Nir Bloch,Yoav Atsmon-Raz,Ehud Gazit,Guy Jacoby,Oren Regev,Maxim Varenik,Yifat Miller,Roy Beck

doi:10.1038/ncomms14018

Sudipta Mondal, Linda J.W Shimon + Show 9 more

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https://doi.org/10.1038/ncomms14018

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Abstract

Extensive work has been invested in the design of bio-inspired peptide emulsifiers. Yet, none of the formulated surfactants were based on the utilization of the robust conformation and self-assembly tendencies presented by the hydrophobins, which exhibited highest surface activity among all known proteins. Here we show that a minimalist design scheme could be employed to fabricate rigid helical peptides to mimic the rigid conformation and the helical amphipathic organization. These designer building blocks, containing natural non-coded α-aminoisobutyric acid (Aib), form superhelical assemblies as confirmed by crystallography and microscopy. The peptide sequence is amenable to structural modularity and provides the highest stable emulsions reported so far for peptide and protein emulsifiers. Moreover, we establish the ability of short peptides to perform the dual functions of emulsifiers and thickeners, a feature that typically requires synergistic effects of surfactants and polysaccharides. This work provides a different paradigm for the molecular engineering of bioemulsifiers.

Highlights

Extensive work has been invested in the design of bio-inspired peptide emulsifiers
Stability in emulsion formulation is accomplished by the addition of non-adsorbing polymers, such as different polysaccharides, including carboxymethyl cellulose and xanthan gum, which increases the viscosity of the bulk continuous phase to retard the coalescence of droplets and creaming—the major destabilizing processes[7]
A recent finding suggested that commonly used food grade surfactants such as Tween-80 and carboxymethyl cellulose are linked to the increase in inflammatory bowel disease observed since the mid-twentieth century and induced low-grade inflammation and obesity-metabolic syndrome in wild-type hosts[8]

Summary

Introduction

None of the formulated surfactants were based on the utilization of the robust conformation and self-assembly tendencies presented by the hydrophobins, which exhibited highest surface activity among all known proteins. Hydrophobins represent the second class of protein surfactants that maintained the native conformational state throughout the interfacial self-assembly processes[14] They exhibit the highest surface activity among all known proteins and shows preferential adsorptions at the hydrophobic–hydrophilic interfaces in the presence of other proteins[15]. The design of de novo peptide-based emulsifiers has focused on mimicking proteins with flexible backbone conformations In such pioneering approach, Middelberg and colleagues[18,19] developed a helical peptide surfactant comprising 21 amino acids that formed a switchable cohesive interfacial film assisted by metal ions and produced oil-in-water emulsions with stability against coalescence over 20 h on standing. In an unparalleled manifestation of the structure–function relationship, we observe that the peptide retains its excellent emulsification behaviour even after structural modifications at the core positions

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