Interfacial and Emulsifying Properties of Designed β-Strand Peptides

The structural and surfactant properties of a series of amphipathic β-strand peptides have been studied as a function of pH. Each nine-residue peptide has a framework of hydrophobic proline and phenylalanine amino acid residues, alternating with acidic or basic amino acids to give a sequence closely...

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Bibliographic Details
Published in:Langmuir 2010-12, Vol.26 (23), p.17997-18007
Main Author: Dexter, Annette F
Format: Article
Language:English
Subjects:
Adsorption
Chemistry
Circular Dichroism
Colloids: Surfactants and Self-Assembly, Dispersions, Emulsions, Foams
Emulsifying Agents - chemistry
Emulsions
Exact sciences and technology
General and physical chemistry
Hydrogen-Ion Concentration
Ions
Models, Statistical
Peptides - chemistry
Phenylalanine - chemistry
Proline - chemistry
Protein Conformation
Protein Structure, Secondary
Surface physical chemistry
Surface Properties
Surface-Active Agents - chemistry
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Summary:The structural and surfactant properties of a series of amphipathic β-strand peptides have been studied as a function of pH. Each nine-residue peptide has a framework of hydrophobic proline and phenylalanine amino acid residues, alternating with acidic or basic amino acids to give a sequence closely related to known β-sheet formers. Surface activity, interfacial mechanical properties, electronic circular dichroism (ECD), droplet sizing and zeta potential measurements were used to gain an overview of the peptide behavior as the molecular charge varied from ±4 to 0 with pH. ECD data suggest that the peptides form polyproline-type helices in bulk aqueous solution when highly charged, but may fold to β-hairpins rather than β-sheets when uncharged. In the uncharged state, the peptides adsorb readily at a macroscopic fluid interface to form mechanically strong interfacial films, but tend to give large droplet sizes on emulsification, apparently due to flocculation at a low droplet zeta potential. In contrast, highly charged peptide states gave a low interfacial coverage, but retained good emulsifying activity as judged by droplet size. Best emulsification was generally seen for intermediate charged states of the peptides, possibly representing a compromise between droplet zeta potential and interfacial binding affinity. The emulsifying properties of β-strand peptides have not been previously reported. Understanding the interfacial properties of such peptides is important to their potential development as biosurfactants.
ISSN:0743-7463
1520-5827
DOI:10.1021/la103471j