title: Complex coacervates of lactotransferrin and β-lactoglobulin.
abstract: OBJECTIVE
  Oppositely charged proteins should interact and form complex coacervates or precipitates at the correct mixing ratios and under defined pH conditions.
  
  
  METHODS
  The cationic protein lactotransferrin (LF) was mixed with the anionic protein β-lactoglobulin (B-Lg) at a range of pH and mixing ratios. Complexation was monitored through turbidity and zeta potential measurements.
  
  
  RESULTS
  Complexation between LF and B-Lg did occur and complex coacervates were formed. This behaviour for globular proteins is rare. The charge ratio's of LF:B-Lg varies with pH due to changing (de) protonation of the proteins. Nevertheless we found that the complexes have a constant stoichiometry LF:B-Lg=1:3 at all pH's, due to charge regularization. At the turbidity maximum the zeta potential of complexes is close to zero, indicating charge neutrality; this is required when the complexes form a new concentrated liquid phase, as this must be electrically neutral. Complexes were formed in pH region 5-7.3. On addition of salt (NaCl) complexation is diminished and disappears at a salt concentration of about 100 mMol. The coacervate phase has a very viscous consistency. If we consider the proteins as colloidal particles then the formed complex coacervate phase may have a structure that resembles a molten salt comparable to, for example, AlCl3.
authors: Fonterra Research and Development Centre, Private Bag 11029, Dairy Farm Road, Palmerston North, New Zealand. Electronic address: skelte.anema@fonterra.com.
authors: Skelte G
authors: SG
authors: Anema
authors: Van 't Hoff Laboratory for Physical and Colloid Chemistry, Padualaan 8, Utrecht University, The Netherlands; NIZO Food Research, PO Box 20, 6710 BA Ede, The Netherlands. Electronic address: C.G.deKruif@UU.NL.
authors: C G Kees
authors: CG
authors: de Kruif
mesh_terms: D006863:Hydrogen-Ion Concentration; D007781:Lactoferrin / Q000737:chemistry*; D007782:Lactoglobulins / Q000737:chemistry*
chemical_list: D007782:Lactoglobulins; D007781:Lactoferrin
keywords: Complex coacervation; Lactoferrin; Lactotransferrin; Molten salt structure; pH; β-Lactoglobulin