So let's take red and blue. So if we examine the charge value on this hydrogen, because the nitrogen is more electronegative than the hydrogen, what that means is this H atom will bear a partial positive charge. And so these two side chains will basically interact. As shown in this diagram, we have electromagnetic interaction between the oxygen and the H. And what this does is it basically positions this entire side chain of histidine, 157, in the correct orientation so that the next interaction can take place. Now, what exactly is the next interaction? Well, this nitrogen contains two electrons, a lone pair of electrons.