Linear and nonlinear microrheology of lysozyme layers forming at the air-water interface

We report experiments studying the mechanical evolution of layers of the protein lysozyme adsorbing at the air-water interface using passive and active microrheology techniques to investigate the linear and nonlinear rheological response, respectively. Following formation of a new interface, the lin...

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Veröffentlicht in:Soft matter 2014-09, Vol.1 (36), p.751-76
Hauptverfasser: Allan, Daniel B, Firester, Daniel M, Allard, Victor P, Reich, Daniel H, Stebe, Kathleen J, Leheny, Robert L
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Sprache:eng
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Zusammenfassung:We report experiments studying the mechanical evolution of layers of the protein lysozyme adsorbing at the air-water interface using passive and active microrheology techniques to investigate the linear and nonlinear rheological response, respectively. Following formation of a new interface, the linear shear rheology, which we interrogate through the Brownian motion of spherical colloids at the interface, becomes viscoelastic with a complex modulus that has approximately power-law frequency dependence. The power-law exponent characterizing this frequency dependence decreases steadily with increasing layer age. Meanwhile, the nonlinear microrheology, probed via the rotational motion of magnetic nanowires at the interface, reveals a layer response characteristic of a shear-thinning power-law fluid with a flow index that decreases with age. We discuss two possible frameworks for understanding this mechanical evolution: gelation and the formation of a soft glass phase. Microrheology tracks the evolution in the linear and nonlinear mechanical properties of layers of the protein lysozyme adsorbing at the air-water interface as the layers undergo a viscoelastic transition.
ISSN:1744-683X
1744-6848
DOI:10.1039/c4sm00484a