The extensional viscoelasticity of protein-coated interfaces

Dimitrijev-Dwyer, Mirjana and Middelberg, Anton P. J. (2011) The extensional viscoelasticity of protein-coated interfaces. Soft Matter, 7 17: 7772-7781. doi:10.1039/c1sm05253e

Author Dimitrijev-Dwyer, Mirjana
Middelberg, Anton P. J.
Title The extensional viscoelasticity of protein-coated interfaces
Journal name Soft Matter   Check publisher's open access policy
ISSN 1744-683X
Publication date 2011-09-07
Sub-type Article (original research)
DOI 10.1039/c1sm05253e
Open Access Status Not Open Access
Volume 7
Issue 17
Start page 7772
End page 7781
Total pages 10
Place of publication Cambridge, United Kingdom
Publisher Royal Society of Chemistry
Language eng
Formatted abstract
In shear or dilational testing, the interfacial rheology of a protein film adsorbed at a fluid–fluid interface is often determined by its response to dynamic deformation. In order to extract characterising parameters from the response data, a model must be assumed in order to fit the response, yet the assumption is difficult to validate due to the limited strain range accessible by most instruments. In this work, a modelling approach was developed to extract characterising parameters from stress–strain curves measured in a high-strain extensional mode of deformation. This mode of testing is insensitive to interfacial tension gradients, making it particularly useful for the study of interfacially adsorbed materials, such as proteins, where the relationship between interfacial tension and interfacial rheology is complex. A four-parameter version of the Generalised Maxwell Model (GMM) for three-dimensional viscoelastic materials successfully describes the response of a two-dimensional β-lactoglobulin interfacial film over a full linear strain range of 0–100%. The GMM asserts that viscoelastic relaxation occurs on multiple timescales, and in this case the two associated time constants give new insights into the nature of interfacial rheology, and its dependence on mass transfer with the bulk solution. In particular, washing out protein from the bulk solution has little effect on the initial response of the system, but a significant effect on the larger-strain response. Fitting a smaller strain range with a less parameterised model (e.g. 0–5% strain fitted with 2 parameters, or 0–20% fitted with 3 parameters) yielded a result that was reasonable up to the strain rate fitted, although the model did not predict well the response to greater strains. The major consequence is that unless a strain range large enough to allow significant influence of viscosity on observed response is tested, unreliable values of viscosity may be determined. Three other common proteins (lysozyme, bovine serum albumin and β-casein) were also tested. In each case, the films showed viscoelastic behaviour that could be well described by the 4-parameter GMM, allowing the viscous components for these protein films to be estimated more accurately than has been possible to date.
Keyword Dynamic surface-properties
Liquid interfaces
Adsorption layers
Fluid interfaces
Hexadecane/water interface
Air/water interface
Dilational behavior
Flexible proteins
Q-Index Code C1
Q-Index Status Confirmed Code
Institutional Status UQ

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Created: Sun, 04 Sep 2011, 11:01:35 EST by System User on behalf of Centre for Biomolecular Engineering