Document Detail

Compression and shear surface rheology in spread layers of beta-casein and beta-lactoglobulin.
MedLine Citation:
PMID:  17234202     Owner:  NLM     Status:  PubMed-not-MEDLINE    
We investigate the surface viscoelasticity of beta-lactoglobulin and beta-casein spread surface monolayers using a recently discovered method. Step compressions are performed, and the surface pressure is measured as a function of time. This is a common experiment for surface monolayers. However in our experiments the pressure is recorded by two perpendicular sensors, parallel and perpendicular to the compression direction. This enables us to clearly measure the time relaxation of both the compression and shear moduli, at the same time, in a single experiment, and with a standard apparatus. beta-Lactoglobulin and beta-casein monolayers are interesting because of their importance in food science and because they exhibit universally slow dynamical behavior that is still not fully understood. Our results confirm that the compressional modulus dominates the total viscoelastic response in both proteins. Indeed for beta-casein we confirm that the shear modulus is always negligible, i.e., the layer is in a fluid state. In beta-lactoglobulin a finite shear modulus emerges above a critical concentration. We emphasize that in Langmuir trough dynamic experiments the surface pressure should be measured in both the compression and the perpendicular directions.
Pietro Cicuta
Publication Detail:
Type:  Journal Article     Date:  2006-12-23
Journal Detail:
Title:  Journal of colloid and interface science     Volume:  308     ISSN:  0021-9797     ISO Abbreviation:  J Colloid Interface Sci     Publication Date:  2007 Apr 
Date Detail:
Created Date:  2007-02-12     Completed Date:  2007-05-15     Revised Date:  2009-11-11    
Medline Journal Info:
Nlm Unique ID:  0043125     Medline TA:  J Colloid Interface Sci     Country:  United States    
Other Details:
Languages:  eng     Pagination:  93-9     Citation Subset:  -    
Cavendish Laboratory and Nanoscience Center, J.J. Thomson Avenue, Cambridge CB3 0HE, UK.
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