Spectroscopic studies on the interaction between novel polyvinylthiol-functionalized silver nanoparticles with lysozyme

• Ag-PVT nanoparticle quenched the fluorescence of lysozyme as a result of complex formation.
• Binding of Ag-PVT nanoparticles also induces secondary structural changes of the lysozyme.
• Appearance of blue shift in case of synchronous spectra signifies the involvement of hydrophobic forces in the interaction.

Silver nanoparticles were functionalized with polyvinylthiol (Ag-PVT) and their effect on the conformation of hen-egg white lysozyme was seen by means of spectroscopic techniques, viz., UV visible, fluorescence (intrinsic and synchronous), resonance Rayleigh scattering and circular dichroism. UV absorption spectra of lysozyme show a hyperchromic shift on the addition of Ag-PVT nanoparticles indicating the complex formation between the two. The interaction between lysozyme and Ag-PVT nanoparticles was takes place via static quenching with 1:1 binding ratio as revealed by the analysis of fluorescence measurements. Circular dichroism spectroscopic data show a decrease in α-helical content of lysozyme on interaction with Ag-PVT nanoparticles which was due to the partial unfolding of the protein. Synchronous fluorescence spectroscopy disclosed that the microenvironments of both tryptophan and tyrosine residues were perturbed in the presence of Ag-PVT nanoparticles and perturbation in the tryptophan environment was more prominent. Rayleigh scattering (RRS) intensity increases on increasing the Ag-PVT nanoparticles concentration till it reaches to the saturation. The RRS intensity increases four times as compared to the native protein indicating the possibility of protein aggregation at higher concentrations of nanoparticles.

Far-UV CD spectra of interaction of lysozyme with Ag-PVT.Figure optionsDownload as PowerPoint slide