Electron transfer between horse heart and Candida krusei cytochromes c in the free and bound states.

This research article explores the electron transfer process between horse heart and Candida krusei cytochromes c in both unbound and bound states. The findings demonstrated that electron transfer rates increased when the cytochromes were bound, hypothesizing that this is due to an increase in the collision frequency when concentrated on the phosvitin molecule.

Electron Exchange Between Two Species Cytochromes

• The study investigated the electron transfer between two species of cytochromes c, one from a horse heart and the other from a yeast species known as Candida krusei.
• The transfer process was examined under both free and bound states, with the bound state involving phosvitin, a phosphoprotein found in egg yolk.
• The researchers used difference spectrum and stopped-flow methods to observe and measure the electron transfer events.
• The results showed that electrons can be exchanged between the cytochromes c of the two species, confirming interspecies electron compatibility.

Equilibrium Constants And Electron Transfer Rates

• The equilibrium constants of the electron transfer reactions for both the free and the phosvitin-bound forms were discovered to be close to one in certain conditions. This indicates that the rates of forward and reverse reactions are approximately equal.
• Under the same conditions, the scientists estimated the electron transfer rate for the free form of cytochrome c to be between 20,000 and 30,000 per molar per second.
• The transfer rate for the phosvitin-bound form was observed to increase as the binding ratio increased, until it reached around half of the maximum. Beyond this point, the rate remained almost constant up to the maximum.

Implications Of The Findings

• The maximal electron exchange rate was found to be about 2 million per molar per second, which is between 60 and 70 times faster than the rate for the free form at the same cytochrome c concentration.
• The researchers found that the activation energy required for the electron transfer reaction was the same for both the bound and unbound forms of cytochrome c, around 10 kilocalories per mole.
• The study concluded that the acceleration of the electron transfer rate for bound cytochromes c is likely due to an increase in collision frequency when the cytochrome c is concentrated on the phosvitin molecule. This could potentially have significant implications for our understanding of electron transfer and collision processes in biochemical reactions.