Chicken egg white lysozyme structural and functional changes in its interaction with different size super paramagnetic nanoparticles (SPION)

Lysozyme is an antibacterial enzyme and a part of the innate immune system in animals. This protein includes on polypeptide chain with 14.3 kD weight and 129 amino acids and five helical structure, which have important roles in lysozyme activity. The amino acid sequence and 3D structure of Hen Egg Withe Lysozyme had known in 1965, so its structure, folding and stability have been well known and investigated till now. On the other hand, accessibility, small size and high solubility in aqueous environment makes HEW-Lysozyme a suitable model protein in structural and functional study of proteins. Superparamagnetic iron oxide nanoparticles (SPIONs) with Fe3O4 molecular composition are taken into consideration in protein interactions and drug delivery. In attention to importance of SPIONs in nanomedicine and drug delivery systems, investigation in interaction between SPION and a model protein and structural and functional changes could be helpful. SPIONs with 20, 50 and 100 nm size were chosen. UV-visible spectroscopy study showed a protein-nanoparticle interaction. Circular dichroism was used in order to measure changes in the secondary structure of lysozyme in interaction with SPIONs and showed a remarkable decrease in helical structure of the protein. Activity and enzymatic properties of SPION bonded lysozyme changed due to helical decrease.

Keywords:

Lysozyme , protein structure , protein function , Nano-Bio interaction , SPION