Unfolding and inactivation of proteins by counterions in protein-nanoparticles interaction

作者：Ghosh Goutam^*; Gaikwad Pallavi S; Panicker Lata; Nath Bimalendu B; Mukhopadhyaya Rita^*

来源：Colloids and Surfaces B: Biointerfaces , 2016, 145: 194-200.

DOI：10.1016/j.colsurfb.2016.04.053

• Functional iron oxide nanoparticles
• Structure-function relationship of proteins
• Protein's secondary structure
• Circular dichroism
• Optical density
• Bioassay

In this work, the structure and activity of proteins; such as, hen egg lysozyme (HEWL) and calf intestine alkaline phosphatase (CIAP); have been investigated after incubation with surface coated iron oxide nanoparticles (IONPs) in water. IONPs were coated with counterions bound charge-ligands and were named as the charge-ligand counterions iron oxide nanoparticles (CLC-IONPs). The coating was done with tri-lithium citrate (TLC) and tri-potassium citrate (TKC) to have negative surface charge of CLCIONPs and Li+ and K+, respectively, as counterions. To have positive surface charge, IONPs were coated with cetylpyridinium chloride (CPC) and cetylpyridinium iodide (CPI) having Cl- and I-, respectively, as counterions. The secondary structure of proteins was measured using far ultraviolet circular dichroism (CD) spectroscopy which showed that both proteins were irreversibly unfolded after incubation with CLC-IONPs. The unfolded proteins were seen to be functionally inactive, as confirmed through their activity assays, i.e., HEWL with Escherichia coli (E. coil) and CLAP with para-nitrophenyl phosphate (pNPP). Additionally, we have observed that monomeric hemoglobin (Hb) from radio-resistant insect Chironomus ramosus (ChHb) was also partially unfolded upon interaction with CLC-IONP5. This work clearly shows the role of counterions in protein inactivation via protein-nanoparticles interaction and, therefore, CLC-IONPs could be used for therapeutic purpose.

• 出版日期2016-9-1