And so that is known as the hydrophobic effect. And these base cells will interact via the hydrophobic interactions and that will be a stabilizing effect. So we see that we have hydrogen bonds, we have London dispersion forces and we have the hydrophobic effect. That basically ensures that the double helix is a favorable structure. Now the only type of nonfavorable interaction is basically the interaction between the phosphate groups. So notice that this phosphate group has a negative charge, this phosphate group also has a negative charge.