Human serum albumin at the air-water interface and its interaction with nanoparticles

Abstract

The adsorption mechanism and structure of human serum albumin (fatted and defatted variants) at the air-water interface was investigated using a combination of complementary x-ray and neutron reflectometry. The studies showed that the presence of fatty acid alters the surface activity of the protein. From x-ray and neutron reflectivity measurements, human serum albumin (regardless of the presence or absence of fatty acid) showed an adsorbed structure that is inconsistent with its native solution state. Studies with denaturants found that the air-water interface has a denaturing effect on the tertiary structure of the protein, equivalent to a 1 M guanidinium chloride solution. The interaction of human serum albumin with negatively charged silica nanoparticles were shown to be highly electrostatic in nature and the strength of their interaction can be controlled by the solution pH. Contrast variation in neutron reflectivity was applied to extract compositional information about the binding ratios of serum albumin to silica nanoparticles under different protein concentrations.