P. Aymard et al., THE EFFECT OF TEMPERATURE AND IONIC-STRENGTH ON THE DIMERIZATION OF BETA-LACTOGLOBULIN, International journal of biological macromolecules, 19(3), 1996, pp. 213-221
Bovine beta-lactoglobulin is a globular whey protein that associates p
artly and reversibly in dimers in the native state. Static and dynamic
light scattering techniques have been used to determine the relative
amount of monomers and dimers, and to estimate their size and shape in
different conditions. The effect of the ionic strength on the dimeris
ation has been studied at pH 2, where the protein is highly charged. A
simple model, taking into account the monomer-dimer equilibrium and v
irial interactions has been used. The strength of the interactions dep
ends on the amount of added salt, i.e. ionic strength, and influences
the dimer dissociation. When the ionic strength decreases, the equilib
rium is shifted towards the monomeric form. The dissociation, however,
is only complete at very low concentration. The effect of temperature
has been studied at pH 7 and low concentration where virial interacti
ons are negligible. The dissociation increases with increasing tempera
ture (5 degrees C-76 degrees C). At high temperatures, protein-protein
aggregation is fast, even at low concentration. The temperature depen
dence can be described using a simple Van't Hoff model, even at temper
atures where aggregation occurs. The ionic strength and temperature de
pendence both indicate that beta-lactoglobulin solutions have to be co
nsidered as a mixture of monomers and dimers.