The effects of pH, temperature, and buffer concentration on the self-assembling behavior, secondary structure, and surface hydrophobicity of donkey and bovine β-casein

Bovine milk β‐casein: Structure, properties, isolation, and targeted application of isolated products

“…Digestibility and sources of nutrient supply β-Casein has a variety of important biological functions due to its special structure and versatile properties (Zhang et al, 2024). First of all, β-casein, as an important component of casein in breast milk protein, has a high similarity to the composition and structure of breast β-casein, which can provide abundant amino acids for mammals (Liu, Li, et al, 2014).…”

The Aggregated and Micellar Forms of β-Casein Purified from Donkey and Bovine Milk Present Potential as Carriers for Bioactive Nutritional Compounds

“…In particular, the donkey β-CN self-association and micellization are mainly due to the polyproline II helical structure that allow protein−protein interactions and to the promotion of a hydrophobic α-helix in the C-terminal domain. 43 The secondary structure composition of donkey β-CN at pH and temperature values ranging from 6.0 to 9.0 and 10 to 40 °C, respectively, is shown in Table 2.…”

“…Additionally, our previous research characterized the secondary structure of donkey and bovine β-CN using circular dichroism spectroscopy, showing that with decreasing pH values and increasing temperature, the α-helix content increases while the unordered structure decreases. 43 The polyproline II helical structure could favor protein−protein interactions, along with the promotion of a hydrophobic αhelix in the C-terminal domain and play a significant role as a structural determinant in the self-association and micellization of donkey and bovine β-CNs.…”

“…This evidence was proved by spectrofluorimetric analysis that showed how at the lowest pH value (6.0), the highest temperature (40 °C) and at a ionic strength of 250 mM there is a structural rearrangement that leads to an increment of the surface hydrophobicity. 43 It was thus concluded that the micellization of β-CN depends on both hydrophobic interactions and electrostatic repulsions since at low pH (6.0) the acidic residues are protonated, and this leads to a reduction of the phosphoserine residues charges on the N-terminal domain of β-CN, consequently the electrostatic repulsions are diminished and the self-assembling into micelles is favored.…”

“…These results indicate that in both donkey and bovine β-CNs pH of 6 and the temperature of 40 °C are the conditions that favor the micellization process that is accompanied by an increment of the ordered secondary structure (mainly a-helix) and poly (Pro)­II helix-like conformations. In particular, the donkey β-CN self-association and micellization are mainly due to the polyproline II helical structure that allow protein–protein interactions and to the promotion of a hydrophobic α-helix in the C-terminal domain …”