Electrochemical Characterization and Bioelectrocatalytic H2O2 Sensing of Non‐Symbiotic Hexa‐Coordinated Sugar Beet Hemoglobins

Abstract

AbstractThe biological role of non‐symbiotic plant hemoglobins (Hbs) is not well understood. It may involve sensing and signaling of reactive nitrogen and oxygen species–a property that can be used in electrochemical sensing. Here, we electrochemically studied two novel non‐symbiotic Beta vulgaris Hbs: BvHb1.2 and BvHb2 expressed in E. coli. At pH 7, we observed close potentials of their Fe2+/3+ hemes, −349 mV for BvHb1.2 and −345/−457 mV vs. Ag/AgCl for the “open” penta‐/“closed” hexa‐coordinated states of BvHb2. BvHbs bound and bioelectrocatalytically reduced O2 and H2O2 at potentials significantly exceeding their Fe2+/3+ heme potentials. BvHb2, with the onset of H2O2 reduction at 370 mV, enabled O2‐interference‐free 10 μM H2O2 detection at 0 mV, with a 87 nA μM−1 cm−2 sensitivity comparable to some peroxidases. The results underpin broad electrochemical applications of BvHbs in the electroanalysis of reactive species and in electrochemical biotransformations.