And we'll see, we'll talk about the actual protein called calmodulent that is used to detect this increase in concentration of calcium. Now, let's move on to fact number two about calcium that makes it such a prevalent secondary messenger molecule. So calcium ions interact strongly with proteins. Why? Well, calcium ions have a charge of positive two. And we know from Coulomb's law that the greater the charge is, the greater that interaction is, the greater that electrostatic force is.