Ibuprofen and Propofol Cobinding Effect on Human Serum Albumin Unfolding in Urea

Abstract

The unfolding pathway of the defatted human serum albumin (HSA) binding ibuprofen and propofol has been studied by using small-angle X-ray scattering (SAXS) and the support of circular dichroism data. A set of HSA solutions with urea concentrations between 0.00 and 9.00 M was analyzed, and the singular value decomposition method applied to the complete SAXS data set allowed us to distinguish four different states in solution. Besides the native and unfolded forms, two intermediates I1 and I2 have been identified, and the low-resolution structures of these states were obtained by exploiting both ab initio and rigid body fitting methods. The I1 structure was characterized by only one open domain (domain I, which does not host a binding site for either of the ligands), whereas I2 presents only one closed domain (domain III). A direct comparison with the unfolding pathway of the HSA:Ibu complex (Galantini et al. Biophys. Chem. 2010, 147, 111-122) pointed out that the presence of propofol as a second ligand, located in subdomain IIIB, leads to the appearance of an intermediate with two closed domains (domains II and III), which are those that accommodate the ligands. Moreover, the equilibrium between I2 and the unfolded form is slightly shifted toward higher urea concentrations. These results suggest that the cobinding significantly hinders the unfolding process.

Multi-drug delivery system based on lipid membrane mimetic coated nano-hydroxyapatite formulations

“…Ibu-BSA complex required 1.8 times of denaturant concentration to attain a 50% of unfolding and increased the free energy of stabilization compared to free BSA, Table 3. Taking into account the obtained results, Ibuprofen released from multi-drug delivery system generated a reduction of BSA unfolding in total agreement to literature data validating its activity (Del Giudice et al, 2014).…”

“…The activity of Ibuprofen released from multi-drug LMm/nano-HA formulation was evaluated analysing the BSA denaturation process according to Galantini et al (Galantini et al, 2010) and Del Giudice et al (Del Giudice et al, 2014). A 0.207 wt% solution of BSA was prepared dissolving the properly amount of BSA powder in 10 mM phosphate buffer, pH 7.4, with the addition of 11 mM sodium azide as preservative; solution was filtered with a nucleopore filter with a diameter of 100 nm before use.…”

Structural Insights into a Hemoglobin–Albumin Cluster in Aqueous Medium

“…The pair-distance distribution function p ( r ) of Hb-HSA 3 cluster was calculated as the inverse Fourier transformation of I ( q ) into real space, assuming a negligible intermolecular interference contribution (Figure B) . Similar structural SAXS studies of HSA and Hb have been reported. − All p ( r ) features of Hb-HSA 3 cluster demonstrated the existence of oblate-like particles with the maximum diameter ( D max ) of ∼17 nm. The simulated p ( r ) of Hb-HSA 3 cluster was also determined using the structure reconstructed by cryo-TEM images.…”

Structural Response of Human Serum Albumin to Oxidation: Biological Buffer to Local Formation of Hypochlorite

“…In the latter case, the average number of residues found in the extended lobe allowed us to roughly estimate that it was equivalent in size to one of the end-domains of HSA. An alternative modeling approach which assumes the known domain-structure of HSA and was used in the past to model the HSA unfolding in urea, , was then tried to fit the same scattering data. The intact HSA domains II and III and the three loops of domain I were used as structural units interconnected by flexible linkers.…”