How Nanoparticles Modify Adsorbed Proteins: Impact of Silica Nanoparticles on the Hemoglobin Active Site

Abstract

The adsorption of proteins on surfaces has been studied for a long time, but the relationship between the structural and functional properties of the adsorbed protein and the adsorption mechanism remains unclear. Using hemoglobin adsorbed on silica nanoparticles, we have previously shown that hemoglobin’s affinity towards oxygen increases with adsorption. Nevertheless, it was also shown that there were no significant changes in the quaternary and secondary structures. In order to understand the change in activity, we decided in this work to focus on the active sites of hemoglobin, the heme and its iron. After measuring adsorption isotherms of porcine hemoglobin on Ludox silica nanoparticles, we analyzed the structural modifications of adsorbed hemoglobin by X-ray absorption spectroscopy and circular dichroism spectra in the Soret region. It was found that upon adsorption, there were modifications in the heme pocket environment due to changes in the angles of the heme vinyl functions. These alterations can explain the greater affinity observed.

pH-Dependent HEWL-AuNPs Interactions: Optical Study

“…A dense layer of protein changes the size of the nanoparticles, which directly affects the properties of both the particle itself and the protein [ 10 , 11 ]. It is known that when nanoparticles enter the body, the cellular response may be associated with a reaction, not to the nanoparticle material itself but to the layer of protein molecules adsorbed on the surface and the change in secondary structure [ 12 , 13 , 14 ]. Changes in the properties of proteins upon interaction with nanoparticles are thought to depend on many factors, including the properties of the medium (pH, ionic strength, redox potential, etc.)…”