Viscoelasticity of a protein monolayer from anisotropic surface pressure measurements.
We present a method to completely characterize the viscoelasticity of Langmuir monolayers. In contrast to existing techniques, both the compression and shear moduli are determined at the same time, in a single experiment and with a standard apparatus. This approach relies on the measurement of anisotropy in the surface pressure: the tension is measured in orientations perpendicular and parallel to the compression direction. We apply this technique to the study of beta-lactoglobulin spread monolayers, a system that has been shown to develop a shear modulus at high concentration. Beta-lactoglobulin monolayers are interesting both because of their importance in food science and because they exhibit universally slow dynamical behavior that is not fully understood. Our results confirm that the compressional modulus dominates the total viscoelastic response and also provide a complex shear modulus, emerging above a critical concentration. We are able to describe how each of the dynamical response moduli is related to the surface concentration and to the equilibrium osmotic pressure.
Cicuta
P
P
Nanoscience Center, University of Cambridge, J.J. Thomson Avenue, Cambridge CB3 0FF, UK. pc245@cam.ac.uk
Terentjev
E M
EM
D000465:Algorithms; D016880:Anisotropy; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D003198:Computer Simulation; D004548:Elasticity; D007782:Lactoglobulins / Q000032:analysis / Q000737:chemistry*; D008422:Materials Testing / Q000379:methods*; D008567:Membranes, Artificial; D008956:Models, Chemical; D011312:Pressure; D011485:Protein Binding; D013500:Surface Tension; D014783:Viscosity
D020099:Coated Materials, Biocompatible; D007782:Lactoglobulins; D008567:Membranes, Artificial
Adv Colloid Interface Sci. 2001 Jul 27;91(3):437-71
11511044
Faraday Discuss Chem Soc. 1975;59:218-29
1231999
Phys Rev Lett. 2003 Jun 13;90(23):236101
12857273
J Agric Food Chem. 2004 Jun 16;52(12):3930-7
15186119
Phys Rev Lett. 2003 Dec 31;91(26 Pt 1):268302
14754093
Nature. 2000 Jun 1;405(6786):550-1
10850709
Phys Rev Lett. 1995 Oct 2;75(14):2770-2773
10059400
Nat Mater. 2002 Nov;1(3):145-6
12618795
Adv Colloid Interface Sci. 1986 Sep;25(4):341-85
3333132
Phys Rev Lett. 2004 Jun 25;92(25 Pt 1):255503
15245024