Aggregation Behavior of Bovine κ- and β‑Casein Studied with Small Angle Neutron Scattering, Light Scattering, and Cryogenic Transmission Electron Microscopy

• Published in: Langmuir Vol. 28; no. 38; pp. 13577 - 13589
• Main Authors: Ossowski, Sofie, Jackson, Andrew, Obiols-Rabasa, Marc, Holt, Carl, Lenton, Samuel, Porcar, Lionel, Paulsson, Marie, Nylander, Tommy
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 25.09.2012
• Subjects: agitation; Animals; Annan teknik; beta-casein; calcium; calcium phosphates; Caseins - chemistry; Cattle; Chemical Sciences; Chemistry; Colloidal state and disperse state; Engineering and Technology; Exact sciences and technology; Fysikalisk kemi; Fysikalisk kemi (Här ingår: Yt- och kolloidkemi); General and physical chemistry; kappa-casein; Kemi; Light; light scattering; micelles; Micelles. Thin films; Microscopy, Electron, Transmission; Natural Sciences; Naturvetenskap; neutrons; Other Engineering and Technologies; Physical Chemistry; Physical Chemistry (including Surface- and Colloid Chemistry); Scattering, Radiation; Teknik; Temperature; transmission electron microscopy; Self assembly; Agitation; Structure stability; Bovine; Calcium; Growth; Light scattering; Micelle; Calcium phosphate; Protein; Aggregation; Vertebrata; Self association; Mammalia; Transmission electron microscopy; Casein; Small angle neutron scattering; Neutron scattering; Artiodactyla; Structure; Ungulata
• ISSN: 0743-7463; 1520-5827; 1520-5827
• DOI: 10.1021/la302416p

In the native bovine casein micelle the calcium sensitive caseins (αS1-, αS2- and β-casein) sequester amorphous calcium phosphate in nanometer-sized clusters, whereas the calcium-insensitive κ-casein limits the growth of the micelle. In this paper, we further investigate the self-association of κ- and β-casein, which are two of the key proteins that control the substructure of the milk casein micelle, using neutron and light scattering techniques and cryogenic transmission electron microscopy. Results demonstrate that κ-casein can, apart from the known self-assembly, form amyloid-like fibrils already at temperatures of 25 °C when subject to agitation. This extended aggregation behavior of κ-casein is inhibited by β-casein, as reported by others. These findings have implications for the structure and stability of casein micelles. The neutron scattering data was used to gain information on the self-assembly structure of κ-casein. β-Casein shows similar self-association behavior as κ-casein, but unlike κ-casein, the self-association exhibits temperature dependence within the studied temperatures (6 and 25 °C). Here, we will discuss our extended study of the known self-assembly of casein in the context of the fibrillation of κ-casein.