Cytochrome c (cyt c) is one of the most studied conjugated proteins due to its electron-transfer properties and ability to regulate the processes involved in homeostasis or apoptosis. Here we report an electrochemical strategy for investigating the electroactivity of cyt c and its analogs with a disrupted heme moiety, i.e. apocytochrome c (acyt c) and porphyrin cytochrome c (pcyt c). The electrochemical data are supplemented with low-temperature and spin-probe electron paramagnetic resonance (EPR) spectroscopy. The main contribution of this report is a complex evaluation of cyt c reduction and oxidation at the level of surface-localized amino acid residues and the heme moiety in a single electrochemical scan. The electrochemical pattern of cyt c is substantially different to both analogs acyt c and pcyt c, which could be applicable in further studies on the redox properties and structural stability of cytochromes and other hemeproteins.

Department of Medical Chemistry and Biochemistry Faculty of Medicine and Dentistry Palacky University Hnevotinska 3 Olomouc 775 15 Czech Republic

Department of Medical Chemistry and Biochemistry Faculty of Medicine and Dentistry Palacky University Hnevotinska 3 Olomouc 775 15 Czech Republic; Faculty of Chemistry Biological and Chemical Research Centre University of Warsaw Zwirki i Wigury 101 02 089 Warsaw Poland

Faculty of Physical Chemistry University of Belgrade Studentski trg 12 16 Belgrade Serbia

Regional Centre for Applied Molecular Oncology Masaryk Memorial Cancer Institute Zluty kopec 7 Brno 656 53 Czech Republic

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Electrochemistry in sensing of molecular interactions of proteins and their behavior in an electric field