TY - JOUR
T1 - Surface shear rheology of adsorption layers from the protein HFBII hydrophobin
T2 - Effect of added β-casein
AU - Radulova, Gergana M.
AU - Golemanov, Konstantin
AU - Danov, Krassimir D.
AU - Kralchevsky, Peter A.
AU - Stoyanov, Simeon D.
AU - Arnaudov, Luben N.
AU - Blijdenstein, Theodorus B.J.
AU - Pelan, Eddie G.
AU - Lips, Alex
PY - 2012/3/6
Y1 - 2012/3/6
N2 - The surface shear rheology of hydrophobin HFBII adsorption layers is studied in angle-ramp/relaxation regime by means of a rotational rheometer. The behavior of the system is investigated at different shear rates and concentrations of added β-casein. In angle-ramp regime, the experimental data comply with the Maxwell model of viscoelastic behavior. From the fits of the rheological curves with this model, the surface shear elasticity and viscosity, E sh and η sh, are determined at various fixed shear rates. The dependence of η sh on the rate of strain obeys the Herschel-Bulkley law. The data indicate an increasing fluidization (softening) of the layers with the rise of the shear rate. The addition of β-casein leads to more rigid adsorption layers, which exhibit a tendency of faster fluidization at increasing shear rates. In relaxation regime, the system obeys a modified Andrade's (cubic root) law, with two characteristic relaxation times. The fact that the data comply with the Maxwell model in angle-ramp regime, but follow the modified Andrade's low in relaxation regime, can be explained by the different processes occurring in the viscoelastic protein adsorption layer in these two regimes: breakage and restoration of intermolecular bonds at angle-ramp vs solidification of the layer at relaxation.
AB - The surface shear rheology of hydrophobin HFBII adsorption layers is studied in angle-ramp/relaxation regime by means of a rotational rheometer. The behavior of the system is investigated at different shear rates and concentrations of added β-casein. In angle-ramp regime, the experimental data comply with the Maxwell model of viscoelastic behavior. From the fits of the rheological curves with this model, the surface shear elasticity and viscosity, E sh and η sh, are determined at various fixed shear rates. The dependence of η sh on the rate of strain obeys the Herschel-Bulkley law. The data indicate an increasing fluidization (softening) of the layers with the rise of the shear rate. The addition of β-casein leads to more rigid adsorption layers, which exhibit a tendency of faster fluidization at increasing shear rates. In relaxation regime, the system obeys a modified Andrade's (cubic root) law, with two characteristic relaxation times. The fact that the data comply with the Maxwell model in angle-ramp regime, but follow the modified Andrade's low in relaxation regime, can be explained by the different processes occurring in the viscoelastic protein adsorption layer in these two regimes: breakage and restoration of intermolecular bonds at angle-ramp vs solidification of the layer at relaxation.
UR - http://www.scopus.com/inward/record.url?scp=84857834376&partnerID=8YFLogxK
U2 - 10.1021/la205113w
DO - 10.1021/la205113w
M3 - Article
C2 - 22320311
AN - SCOPUS:84857834376
SN - 0743-7463
VL - 28
SP - 4168
EP - 4177
JO - Langmuir
JF - Langmuir
IS - 9
ER -