So what would happen if we add H plus ions into the nucleus? What would happen if we have an acid based reaction that takes place inside that nucleus where we have nothing but pure water and the DNA molecules? Well, basically, this curve describes this situation. This is the Titration curve for pure water. So the y axis is the PH and the x axis is the acid base reaction. So as we go along the x axis, we're essentially adding H plus ions into that solution.