Question

(5) A myoglobin similar to the ex ample we did in class had the protonation of a histidine residue coupled to the oxidation of a heme. The histidine had a pKA of 6.0 when the heme is oxidized and 7.1 when the heme is reduced. At pH 9.5, the reduction potential of the heme s +275 mV vs NHE (a) Draw the thermodynamic box that describes this system (b) Predict the reduction potential at pH 3. (c) The net charge at the iron center really cycles between 0 and+, as the nitrogens at the center of the porphyrin ring have a total net charge of -2. Assuming a dielectric constant of 6, predict the distance between the heme iron and the histidine side chain.

Answer 1

aj When hiotidine .co卢utonatd in myogidin tt to PH dosr. When te, itouasing. Hence, heme ia oidedt