Evidence of changes in hydrophilic/hydrophobic balance and in chemical activity of HSA induced by thermal treatments

Abstract

Samples of human serum albumin (HSA) obtained as a result of heat denaturation followed by refolding controlled by a cooling of the protein solution were studied by several methods: chromatographic measurements, kinetic of the reaction with a water soluble free radical and by electron paramagnetic resonance (EPR) spectroscopy. In this context the interaction of this protein with β-cyclodextrin (β-CD) and sodium dodecyl sulfate (SDS) was also investigated. Reversed phase thin layer chromatography (RP-TLC) showed changes in lipophylicity of HSA, which are related with the existence of different ensembles of conformers. The UV-Vis absorption spectra had shown the broadening of absorption band of the protein and a hyperchrom effect in the presence of SDS; β-CD reduces the effect of SDS on protein UV-Vis spectra.Kinetic measurements related to the reaction of HSA with a water soluble DPPH type free radical provided evidence that reactivity of the HSA denaturated conformers is higher compared with the natural conformer. The affinity of SDS to the albumins surface and the effect of β-CD on the SDS/protein aggregates were also evident by changes in the EPR spectra of the spin probe CAT16.

EPR and Circular Dichroism Solution Studies on the Interactions of Bovine Serum Albumin with Ionic Surfactants and β-Cyclodextrin

“…The ability of cyclodextrins to prevent or slow a protein aggregation process or otherwise inhibit the interaction between a protein and hydrophobic molecules has already been reported. , Cyclodextrins are capable of complexing hydrophobic moieties, which might be present in some cases at the surface of a protein. In our previous studies on the radical scavenging activity of BSA and HSA, a strong interaction between β-CD and albumins was not revealed. , …”

“…The EPR spectra of CAT16 in BSA solutions reflect a superposition of (a) a component with narrow lines corresponding to the free CAT16 in solution, and (b) a component with broader lines due to restricted mobility, corresponding to the spin probe “bound” to albumin. The interaction of CAT16 with BSA is comparable to that of CAT16 with HSA, as the spectrum of CAT16 in a solution of 10 mg/mL HSA exhibits similar features . The experimental spectra of CAT16 in BSA solutions can be deconvoluted by subtracting the spectrum of CAT16 in buffer solution from the spectrum recorded in BSA (Figure ).…”

“…The interaction of CAT16 with BSA is comparable to that of CAT16 with HSA, as the spectrum of CAT16 in a solution of 10 mg/mL HSA exhibits similar features. 39 The experimental spectra of CAT16 in BSA solutions can be deconvoluted by subtracting the spectrum of CAT16 in buffer solution from the spectrum recorded in BSA (Figure 3). The difference spectrum corresponds to the complex CAT16/BSA and reveals an anisotropic motion.…”

Antioxidant activity of rosemary extracts in solution and embedded in polymeric systems

“…The antioxidant activity of rosemary extract in water was tested in water using the water soluble derivative of DPPH, DPPH-SO 3 Na, which was previously used to evaluate the effect of temperature on the ability of albumins to reduce it (Ionita & Sahini, 2004;Sahini & Ionita, 2011). The UV-VIS spectra for a solution of DPPH-SO 3 Na in water recorded over 3 h revealed that the absorbance at the maximum absorption band of 520 nm was almost constant.…”

Environmental Aspects of Zoonotic Diseases

“…Walter et al (2011) recently reported an indirect proof of clay's role in prions' infectivity perpetuation by analyzing prion-infected deer herd data in the USA in relation to clay soil content. These components have been shown to change proteins' hydrophilic/hydrophobic balance and modulate the oligomerization of membrane proteins in lipid bilayers, which may explain why under basic conditions prions are inactivated (Sahini and Ionita, 2011;Otzen et al, 2007). In environmental water ecosystem (urban sewage and seawater) prions have been shown to have limited survival compared to in buffered solutions such as phosphate buffered saline (Maluquer de Motes et al, 2008).…”