0000000000276303
AUTHOR
Yurij A. Antonov
Joint Aqueous Solutions of Dextran and Bovine Serum Albumin: Coexistence of Three Liquid Phases
The phase diagram of the system water/dextran (DEX)/BSA was measured as well as modeled. On the experimental side, cloud points were determined and the coexisting phases were analyzed. The theoretical calculations use an approach capable of describing solutions of chain polymers and of globular proteins with the same formalism. The required thermodynamic input comes from experiments concerning the binary subsystems, except for the polymer blend for which one interaction parameter had to be adjusted. Both sources of information yield the same essential features: the existence of a large composition area of immiscibility, starting from the subsystem DEX/BSA and extending well into the region …
Inducing mixing of water-in water BSA/dextran emulsion by a strong polyelectrolyte
Abstract We examine whether a small amount of strong polyelectrolyte (dextran sulfate sodium salt/DSS/) can induce mixing in water-in-water bovine serum albumin/dextran (BSA/DEX) emulsion and how intermacromolecular interactions affect its the rheological properties. Addition of DSS to water-in-water emulsion at pH 5.4 leads to its mixing at the DSS/BSA weight ratio, ( q ( DSS / BSA ) ) ≥ 0.07 , a noticeable increase in viscosity and storage modulus (G′). Mixing is reversible: increasing the ionic strength leads to phase separation in the water/BSA/DEX/DSS system. The increase in viscoelasticity results from the interaction of DSS with both macromolecular compounds of the emulsion. We assum…
Phase behavior of aqueous solutions of bovine serum albumin in the presence of dextran, at rest, and under shear.
The demixing conditions for aqueous solutions of bovine serum albumin (BSA, fraction V) and for joint solutions of BSA plus dextran (DEX, M(w) = 2000 kg/mol) were determined by turbidimetric measurements as a function of composition, temperature, and shear rate. Aqueous solutions of BSA phase separate upon heating. Within the region of BSA concentrations between 0.05 and 32 wt %, the demixing temperature, T1, falls from ca. 65 degrees C to an almost constant value of 45 degrees C. Adding DEX to the BSA solutions reduces the homogeneous region of the mixture drastically where the amount of DEX required to lower T1 to 25 degrees C decreases rapidly as the concentration of BSA is raised. Exper…
Liquid/Gas and Liquid/Liquid Phase Equilibria of the System Water/Bovine Serum Albumin
The thermodynamic behavior of the system H2O/BSA was studied at 25 °C within the entire composition range: vapor pressure measurements via head space sampling gas chromatography demonstrate that the attainment of equilibria takes more than one week. A miscibility gap was detected via turbidity and the coexisting phases were analyzed. At 6 °C the two phase region extends from ca. 34 to 40 wt % BSA; it shrinks upon heating. The polymer rich phase is locally ordered, as can be seen under the optical microscope using crossed polarizers. The Flory-Huggins theory turns out to be inappropriate for the modeling of experimental results. A phenomenological expression is employed which uses three adju…
Calorimetric and structural investigation of the interaction between bovine serum albumin and high molecular weight dextran in water.
This work studies specific interactions between a small globular protein and a highly flexible, branched polysaccharide using differential scanning calorimetry (DSC), circular dichroism (CD), fluorescence, and turbidimetry measurements. It uses the system water/bovine serum albumin (BSA)/dextran (D 2000) as a model. Dextran molecules are able to form interpolymeric complexes with BSA in water at both low and high temperatures if the polysaccharide is in excess and if the protein exists in its associated state. It leads to a partial destabilization of the secondary and tertiary structures of the protein and an additional exposure of the hydrophobic tryptophan residues to the surface of globu…