Probing the conformational changes and peroxidase-like activity of cytochrome c upon interaction with iron nanoparticles

Herein, the interaction of iron nanoparticle (Fe-NP) with cytochrome c (Cyt c) was investigated, and a range of techniques such as dynamic light scattering (DLS), zeta potential measurements, static and synchronous fluorescence spectroscopy, near and far circular dichroism (CD) spectroscopy, and ultraviolet–visible (UV–vis) spectroscopy were used to analyze the interaction between Cyt c and Fe-NP. DLS and zeta potential measurements showed that the values of hydrodynamic radius and charge distribution of Fe-NP are 83.95 ± 3.7 nm and 4.5 ± .8 mV, respectively. The fluorescence spectroscopy results demonstrated that the binding of Fe-NP with Cyt c is mediated by hydrogen bonds and van der Waals interactions. Also Fe-NP induced conformational changes in Cyt c and reduced the melting temperature value of Cyt c from 79.18 to 71.33°C. CD experiments of interaction between Fe-NP and Cyt c revealed that the secondary structure of Cyt c with the dominant α-helix structures remained unchanged whereas the tertiary structure and heme position of Cyt c are subjected to remarkable changes. Absorption spectroscopy at 695 nm revealed that Fe-NP considerably disrupt the Fe…S(Met80) bond. In addition, the UV–vis experiment showed the peroxidase-like activity of Cyt c upon interaction with Fe-NP. Hence, the data indicate the Fe-NP results in unfolding of Cyt c and subsequent peroxidase-like activity of denatured species. It was concluded that a comprehensive study of the interaction of Fe-NP with biological system is a crucial step for their potential application as intracellular delivery carriers and medicinal agents.