So we have this hydrogen accepting group that interacts with this hydrogen donating group on the other amino acid. And here we have this hydrogen donating group that interacts with this hydrogen accepting group of the other opposing amino acid. So in the antiparallel beta sheets, we see that the NH and the co groups of an amino acid on one strand interact with the Co and NH groups of the opposing amino acid on the other strand. So we have a one to one perfect interaction between our groups on opposing amino acids. Now, how exactly can this actually exist? Well, let's imagine we have our polypeptide that runs in the following direction.