Every molecule/atom regardless of whether or NOT it is polar, has some attraction for another molecule/atom albeit a week attraction. One can think about it as follows: in two separate atoms electrons are in motion around a nucleus. If the atoms are far away from each other that motion is unrelated in both molecules. as they approach each other, on the other hand, the electric fields start to interact and the motion becomes more similar. (electrons of one atoms would be repelled by the electron of the neighbor) . Thus they INDUCE a dipole in each other.... and therefore a favorable dipolar interaction.
From the description alone it is easy to understand that this is a VERY short range interaction. They must be near enough to each other to initiate similar electron motion. The interaction depends on the inverse of the SIXTH power of distance. (1/r6).
Aslo Included in this equation is the repulsive interaction. The origin of this tem is that atoms are just plain getting TOO close. This is the steric interaction that was described at the beginning of this module.
It was stated at the top that this is a weak interaction. Indeed it is. For example.....Two molecules of Helium gas have so little attraction for one another that they must be cooled to 4 degrees above absolute zero (-456 degree below 0 Fahrenheit or -269 degree below 0 centigrade) in order to make them into a liquid!!!
So a single interaction is extremely week. On the other hand, proteins are made of thousands of atoms tied together. This leads to thousands of weak interactions and can lead to a stable structure. I view this rather like Velcro. Here you have two strips of cloth: one with loops and one with hooks. If you had just one hook / loop pair, you would hardly even notice the amount of effort that it takes to pull the strips apart. But in the real product there are THOUSANDS of hook / loop pairs. Although each ONE contributes a small amount to the holding force, the sum of all of the hook /loop pairs is quite substantial.