The effect of fatty acids, ionic strength, and electric fields on the microscopic dynamics of BSA aggregates

The effects of fatty acids binding to BSA, as well as the ionic strength and weak electric field, are discussed for affecting the stability of BSA suspensions against calcium-induced aggregation. By variation of the ionic strength, in the absence of an external electric field, DLS experiments show that monomer–BSA interactions (in the essentially fatty acid-free case) are overall repulsive but that, nevertheless, aggregation occurs to some extent.

Also, the diffusive properties of different types of BSA are explored under an applied low-AC electric field by means of in situ electric small-angle depolarized DLS experiments, which reveal a significant decrease of the translational BSA–monomer diffusion coefficient with increasing frequency, while the aggregates indicate orientational motion via rotation on applying an electric field.

Figure: Depolarized normalized intensity auto-correlation functions CVH (t) of a BSA1 solution, measured by SAeDLS, with a concentration of 50 mg/mL and at a higher PBS concentration of 115 mM, in the presence of an AC external electric field for various electric field amplitudes (5 V/mm) and frequencies: (A) 5 Hz, (B) 50 Hz, (C) 500 Hz, and (D) 5 kHz. The arrow indicates an increase in the scattering wavevector for the given electric field condition.

(Frontiers in Physics, Published on 20 October 2023 DOI 10.3389/fphy.2023.1282099)