Interaction of manganese nanoparticle with cytochrome c: A multi-spectroscopic study

In this paper, the conformational changes of cytochrome c (cyt c) upon interaction with manganese nanoparticle (Mn-NP) were examined using dynamic light scattering (DLS), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), zeta potential, fluorescence spectroscopy, and circular dichroism (CD) spectroscopy methods. DLS and TEM analysis exhibited the structure of Mn-NP was less than 50 nm. FTIR bands were similar to those reported for Mn-NP. Zeta potential measurements showed positive charge distribution for Mn-NP (4.71 ± 0.71 mV) at pH 7.8. It was revealed that the mechanism of fluorescence quenching incorporated both dynamic and static quenching. Also, binding site and binding constant increased as the temperature is raised. The positive sign of ΔH° and ΔS° suggested that hydrophobic forces are indicative forces in the interaction between cyt c and Mn-NP. Synchronous fluorescence spectra revealed that the conformation of protein was not perturbed around tryptophan (Trp) and tyrosine (Tyr) residues. CD analysis suggested that there was a conformational change at tertiary structure levels of cyt c in the vicinity of phenylalanine (Phe) residues, while the secondary structure of protein was not altered. This study facilitates a deeper insight on the interaction mechanisms between NPs and biological macromolecules.