The peak shapes of apo taTrxR (6 = 59 mV) and 2x taTrxR (6 = 62 mV) are significantly closer to the shape to a theoretical cooperative 2e~ reaction. The decrease in width relative to that in wt taTrxR agrees with our hypothesis in Chapter 3, that the redox signal at 333 K represents the combination of two cooperative 2e~ redox reactions, one per cofactor. We do not observe perfect 2e" peak shape, likely due Nike Chaussures to a slightly heterogeneous mixture of protein interactions with the electrode surface. Figure 4.6 Temperature dependent nature of apo and 2x taTrxR PFV signals in a buffer containing 50 mM HEPES pH 7.0 and 100 mM NaCl with a scan rate of 150 mV/s. (A) Peak separation as a function of temperature. (B) The average peak with at half-height (5) for oxidative and reductive scans as a function of temperature for apo taTrxR (O) and 2x taTrxR (O). Experimental data are compared with the theoretical peak width at half height (5 ~ 3.53(RT/nF)) as a function of Chaussures Nike temperature for n- 1 (—) and n = 2 (—) redox reactions. 43.5 pH dependence of apofczTrxR and 2x toTrxR midpoint potentials Using apo and 2x taTrxR, we can monitor the proton coupling of the disulfide and flavin redox reactions by measuring the midpoint potential over a range of pHs. Our previous work did include measuring the pH dependence of toTrxR midpoint potentials, however, since the redox potentials of the disulfide and flavin were indistinguishable we could not differentiate the proton coupling properties of the two cofactors.