Why is only guanine capable of forming complex structures like G-quadruplexes? What are the possible reasons behind it. In most of the references I have seen, they mentioned it can form but they did not say why it has such capacity?
I think it is because guanine has the three functions that form hydrogen bonds, multihydrogen bonds, like, CO, 2NH, NH2 functions. As a matter of fact the IR spectrum of DNA is represented almost 90 per cent by the IR spectrum of guanine!
I think it is for the 3 hydrogen bond forming centre as well as the ability to form the square planar structure(guanine tetrad) via Hoogsten base pair formation .Which give stability to the system