Gold and Magnetite Nanoparticles as Sensors of Conformational Changes in Proteins

The folding of proteins was investigated by using helical polypeptides attached to gold or magnetite nanoparticle surfaces. Depending on type and loading of the polypeptide on the surface of gold nanoparticles, pH, temperature, presence of different ions in the solution, and influence of different mechanical factors, conformational changes in the polypeptide occurred. The aggregation of the gold nanoparticles related to the folding of the polypeptide caused shifts in color of the solutions from red to blue that were measured by UV-Vis spectrometry. Different ligands were attached on the surface of magnetite nanoparticles. The resulting structures induced modifications in the characteristics of the superparamagnetic resonance (SRP) spectra of magnetite nanoparticles. Lineshape parameters related to the anisotropy and crystal structure revealed ligand-dependent and temperature-dependent SPR spectra. The attachment of ligands leads further to the possibility of attaching model polypeptides on the magnetite nanoparticles surface for studying protein folding