Alkaline transition of horse heart cytochrome c in the presence of ZnO nanoparticles

The effect of zinc oxide nanoparticles (ZnO NPs) on cytochrome c (cyt c) in alkaline pH was studied with absorption spectroscopy and UV circular dichroism (CD).Spectral data from UV–vis spectroscopy and circular dichroism indicate only small changes in the native structure of the protein at neutral pH after the interaction with ZnO nanoparticles.The stability around the heme crevice of cyt c and therefore the switch of the axial ligand Met80 to Lys which occurs in conditions of higher pH was proven following the interaction of cytochrome c with ZnO nanoparticles. The formation of cyt c-ZnO NPs complex based on electrostatic attraction was accompanied by a significant increase in the apparent pKa constant of the alkaline transition of cyt c.

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► The influence of ZnO nanoparticles to the cytochrome c in alkaline pH have been studied.
► The structural stability around the heme of cyt c assembled with ZnO nanoparticles was increased.
► The pKa constant of cyt c-ZnO complex was took place to the higher value.
► The alkaline transition of cytochrome c in the presence of ZnO nanoparticles was more cooperative.