The glass transition behavior of the globular protein bovine serum albumin.
The glass-like transition behavior of concentrated aqueous solutions of bovine serum albumin was examined using rheological techniques. At mass fractions >0.4, there was a marked concentration dependence of viscosity with a glass-like kinetic arrest observed at mass fractions in the region of 0.55. At mass fractions >0.6 the material behaved as a solid with a Young's modulus rising from approximately 20 MPa at a mass fraction of 0.62-1.1 GPa at 0.86. The solid was viscoelastic and exhibited stress relaxation with relaxation times increasing from 33 to 610 s over the same concentration range. The concentration dependence of the osmotic pressure was measured, at intermediate concentrations, using an osmotic stress technique and could be described using a hard sphere model, indicating that the intermolecular interactions were predominantly repulsive. In summary, a major structural relaxation results from the collective motion of the globules at the supra-globule length scale and, at 20 degrees C, this is arrested at water contents of 40% w/w. This appears to be analogous to the glass transition in colloidal hard spheres.
Brownsey
Geoffrey J
GJ
Institute of Food Research, Norwich Research Park, Colney, Norwich, NR4 7UA, UK.
Noel
Timothy R
TR
Parker
Roger
R
Ring
Stephen G
SG
D000818:Animals; D055592:Biophysical Phenomena; D001703:Biophysics; D002417:Cattle; D003102:Colloids; D009995:Osmosis; D017785:Photons; D011092:Polyethylene Glycols; D011312:Pressure; D012212:Rheology; D012709:Serum Albumin / Q000737:chemistry*; D013053:Spectrophotometry; D013314:Stress, Mechanical; D013997:Time Factors; D014867:Water
D003102:Colloids; D012709:Serum Albumin; D014867:Water; D011092:Polyethylene Glycols