Well, because it turns out that if we have that double helix structure, because these bases are too busy forming those hydrogen bonds, they are not able to absorb as much light as the bases in the dissociated form can because these bases here are not forming any bonds. And so they're free to absorb that UV radiation. So if we shine light onto this structure here, these bases will be able to absorb much more UV radiation than in this particular case. Because in this particular case, we have the stacking of these bases and we have vanderbal forces and hydrogen bonds. And those bonds will essentially decrease the amount of UV radiation that can be absorbed by those bases. So how can we measure the dissociation of DNA molecules in solution?