6.12 The midpoint potential of a protein was found to have the following pH dependence. If
this is interpreted as arising from a change in protonation of the cofactor, estimate the pKA
value.
pH Em(mV)2 450
3 430
4 370
5 305
6 250
7 220
8 210
9 2106.13 If reduced cytochrome is added to the oxidized bacterial reaction center, can an electron
be transferred? Assume that the two proteins can dock properly.
6.14 If reduced cytochrome is added to the oxidized photosystem II, can an electron be transferred?
Assume that the two proteins can dock properly.
6.15 Calculate the ionic strength of 0.5 M NaCl.
6.16 Calculate the ionic strength of 0.5 M MgCl 2.
6.17 Discuss why the proposed motion of the Rieske FeS protein plays a role in the function of
the cytochrome bc 1 complex.
6.18 How would the results from fluorescently labeled actin attached to ATP synthase compare
with the biochemical data?