TY - JOUR
T1 - Micellization of bovine β-casein studied by isothermal titration microcalorimetry and cryogenic transmission electron microscopy
AU - Portnaya, Irina
AU - Cogan, Uri
AU - Livney, Yoav D.
AU - Ramon, Ory
AU - Shimoni, Karin
AU - Rosenberg, Moshe
AU - Danino, Dganit
PY - 2006/7/26
Y1 - 2006/7/26
N2 - The association behavior, critical micellization concentration (CMC), and enthalpy of demicellization (ΔHdemic) of bovine β-casein were studied, for the first time by isothermal titration calorimetry, in a pH 7.0 phosphate buffer with 0.1 ionic strength and in pure water. In the buffer solutions, the CMC decreased asymptotically from 0.15 to 0.006 mM as the temperature was raised from 16 to 45°C. ΔHdemic decreased with increasing temperature between 16 and 28°C but increased from 28 to 45 °C. Thermodynamic analysis below 30°C is consistent with the Kegeles shell model, which suggests a stepwise association process. At higher temperatures, this model exhibits limitations, and the micellization becomes much more cooperative. The CMC values in water, measured between 17 and 28°C, decreased with increasing temperature and, expectedly, were higher than those found in the buffer solutions. β-Casein micelles were visualized and characterized, for the first time in their hydrated state, using advanced digital-imaging cryogenic transmission electron microscopy. The images revealed small, oblate micelles, about ∼13 nm in diameter. The micelles shape and dimensions remained nearly constant in the temperature range of 24-35°C.
AB - The association behavior, critical micellization concentration (CMC), and enthalpy of demicellization (ΔHdemic) of bovine β-casein were studied, for the first time by isothermal titration calorimetry, in a pH 7.0 phosphate buffer with 0.1 ionic strength and in pure water. In the buffer solutions, the CMC decreased asymptotically from 0.15 to 0.006 mM as the temperature was raised from 16 to 45°C. ΔHdemic decreased with increasing temperature between 16 and 28°C but increased from 28 to 45 °C. Thermodynamic analysis below 30°C is consistent with the Kegeles shell model, which suggests a stepwise association process. At higher temperatures, this model exhibits limitations, and the micellization becomes much more cooperative. The CMC values in water, measured between 17 and 28°C, decreased with increasing temperature and, expectedly, were higher than those found in the buffer solutions. β-Casein micelles were visualized and characterized, for the first time in their hydrated state, using advanced digital-imaging cryogenic transmission electron microscopy. The images revealed small, oblate micelles, about ∼13 nm in diameter. The micelles shape and dimensions remained nearly constant in the temperature range of 24-35°C.
KW - Cryo-TEM
KW - ITC
KW - Micellization
KW - Self-association
KW - β-Casein
UR - http://www.scopus.com/inward/record.url?scp=33746967183&partnerID=8YFLogxK
U2 - 10.1021/jf060119c
DO - 10.1021/jf060119c
M3 - 文章
C2 - 16848545
AN - SCOPUS:33746967183
SN - 0021-8561
VL - 54
SP - 5555
EP - 5561
JO - Journal of Agricultural and Food Chemistry
JF - Journal of Agricultural and Food Chemistry
IS - 15
ER -