Thermally induced conformational changes and protein–protein interactions of bovine serum albumin in aqueous solution under different pH and ionic strengths as revealed by SAXS measurements

Abstract

Thermal-induced conformational changes and protein-protein interactions of bovine serum albumin (BSA) in aqueous solution are assessed by small angle X-ray scattering (SAXS) at two pH values (7.4 and 9.0) and two ionic strengths (0.1 and 0.5). We demonstrate that Guinier analysis in two ranges of the modulus of the scattering vector allows protein melting and aggregation to be monitored simultaneously, thus providing insights into the mechanism of thermal-induced BSA aggregation. Results of the analysis suggest that at room temperature monomeric and dimeric BSA fractions are present in solution. For low concentrations (<10 mg mL) the monomeric to dimeric fraction ratio is close to 6, the same value we obtained independently in size-exclusion chromatography experiments. For elevated concentrations (20 mg mL and 40 mg mL) a decrease in the dimer fraction occurs. Following heating, dimer formation is observed prior to protein melting, while no higher order aggregates are observed in the 20-60 °C temperature range. In the vicinity of the BSA melting point, higher order aggregates appear and protein molecules exhibit an aggregation burst. Higher ionic strength makes the described effects more pronounced - dimer formation increases at lower temperatures, presumably due to partial screening of electrostatic interactions between protein molecules. Moreover, the melting temperature shifts to higher values upon increasing the protein concentration and pH, indicating that repulsive interactions stabilize the protein structure. The suggested model was verified by the assessment of parameters of protein-protein interaction potentials based on DLVO theory using the global fitting procedure.

Temperature and salt controlled tuning of protein clusters

“…solution has been observed at low protein concentrations in the absence of salt, 34,35 at the high protein concentrations investigated here, the salt-free solutions agree with the picture of an effectively monomeric system. [36][37][38] Previously, 32 cluster formation of BSA in D 2 O was observed upon approaching c* for YCl 3 at constant temperature (295 K), using incoherent QENS. A master curve for D depending only on the ratio c s /c p was found for these conditions.…”

A molecular simulation approach towards the development of universal nanocarriers by studying the pH- and electrostatic-driven changes in the dynamic structure of albumin

“…[22][23][24] Very few studies have been reported on the inter-model transitions at the molecular level for the conformational changes in the protein structure, which are dependent on both the ionic strength and pH. 1,25,26 The tertiary structural motifs of protein refer to its threedimensional structure. The motif conformations depend on many factors, i.e.…”

Functionalisation of a heat-derived and bio-inert albumin hydrogel with extracellular matrix by air plasma treatment

“…Unfortunately, increasing NaCl concentrations resulted in increasing opacity across all hydrogels types. The mechanism of gelation for heat-derived albumin hydrogels are well described in literature [28][29][30][31] , and the differences observed between these three hydrogels are most likely explained by the differences in ionic content and concentrations in all three solvents. However, it was not feasible to determine the effect of specific ions on gelation and hydrogel clarity because of the sheer multitude of permutations between ion combinations and concentrations.…”