Calculation and measurement of semiconduction activation energy and electron mobility in cytochrome oxidase,with evidence that charge carriers are polarons,which may couple oxidation to phosphorylation

It is shown that an electron transport reaction which is rate-limited by electron conduction 4 across a solid biological particle or membrane in accord with Ohm's law should have a first order rate constant approximately proportional to exp (E _a/KT ), whereT is absolute temperature,k is the Boltzmann constant andE _a is the activation energy for semiconduction in the solid particle, where resistance in the semiconductor is proportional to exp (E _a /KT). For two different preparations of cytochrome oxidase, this method yields an average value ofE _a =0.27 ev, which agrees well with direct conductivity measurements on dry solid enzyme, which provide an average value ofE _a =0.26 ev. Electron mobility in dry cytochrome oxidase is estimated to be approximately gm=10^t-5 cm² volt^t-1 sec^t-1. Elovich decay of current in dry cytochrome oxidase was observed, which parallels the Elovich kinetics of cytochrome oxidase activity in yeast observed previously by M:uhlig (1966). Finally, the solid state kinetic theory is used to deduce that conduction of polarons may be involved in cytochrome oxidase activity (1 polaron=1 electron + 1 phonon), which provides a link with the solid state phonon phosphorylation theory of Straub.