A topic on which every scientist has its own opinion with own sets of data. A topic where it’s not clearly understood that on what results to believe.

However, I’m not any kind of scientist but, I like this topic a lot. So after going through a lots of research paper I tried to explain the most feasible mechanism through which a charge is getting transported across the base pairs of DNA.

DNA structure is made up of adenine, guanine, cytosine and thymine. Now, these bases are arranged in the form of a stack in the double helical DNA strand. The aromatic groups of these bases overlap each other to form aromatic interactions and also the pi-orbital of bases overlap because of the formation of various inter and intra strand hydrogen bonding. Now, it has been known that hydrogen bond can participate in the charge transfer of the molecule.

Also, it’s known that the minimum energy required to oxidize the base is around 1.4 volts for guanine. Also, the energy required to transfer the charge from the guanine to next guanine is less as compared to that transferred to adenine. But, as the distance between two guanine molecules increased the energy required to transfer the charge also increases and when the distance between two guanine molecules is three base pairs at that time the energy required to transfer electron to guanine is comparable to that of the energy required to transfer charge to an adenine molecule which is next to the donor guanine molecule. Also, energy required to transfer charge from adenine to adenine is very less as compared to guanine to guanine and guanine to adenine. Also, the rate of charge transfer is almost twice to that compared to guanine to guanine charge transfer and is higher to guanine to adenine transfer by eleven orders of magnitude.

Now, the next question is why the charge does not go to thymine and cytosine?

The answer which I feel is that since the energy to activate them is high so, charge doesn’t stay on it for much time, but get distributed over the base pairs with more concentration towards adenine or guanine.

I say that energy is higher for both thymine and cytosine because both have only one ring respectively while adenine and guanine have two rings each which causes the much better distribution of charge in case of guanine and adenine as compared to thymine and cytosine.