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    pH-Induced interfacial properties of Chaplin E from Streptomyces coelicolor

    Year: 2017

    Journal: Colloid Surf. B-Biointerfaces, Volume 160, DEC 1, page 589–597

    Authors: Dokouhaki, Mina; Hung, Andrew; Prime, Emma L.; Qiao, Greg G.; Day, Li; Gras, Sally L.

    Organizations: Australian Government; ARC Dairy Innovation Hub [IH2010005]; ARC Research Hub for Future Fibres [IH140100018]

    Keywords: Pressure/area isotherm; Surface activity; CD; BAM; TEM

    Chaplin E, or Chp E, is a surface active peptide secreted by Streptomyces coelicolor that adopts different structures depending on solution pH but the effect of these structures on the interfacial properties of Chp E is not known. In experiments paired with simulations, Chp E was found to display pH-dependent interfacial assembly and surface activity. At pH 3.0, Chp E formed an ordered non-amyloidal interfacial film with high surface activity; while at pH 10.0, Chp E self-assembled into a heterogeneous film containing randomly arranged fibrils at the interface that was less surface active compared to the film formed at pH 3.0. In simulations at pH 10.0, Chp E molecules showed a higher propensity for dimerization within the solution phase, lower rate of adsorption to the interface and tighter inter-molecular associations at the interface, consistent with the lower surface activity and smaller interfacial area coverage per molecule measured at this pH compared to at pH 3.0. A model is presented for the role of Chp E in the developmental differentiation of Streptomyces coelicolor, where Chp E contributes to changes in surface tension at low pH and the formation of fibrils on the surface of aerial hyphae at high pH. Our data also suggest Chp E could be a promising surface active agent with functional activity that can be controlled by pH. (C) 2017 Elsevier B.V. All rights reserved.
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