John Hopfield: On the surface of the ten-thousand atom molecule, there is a slight change. A small group of a few atoms on the edge of
the molecule is replaced by another small group of atoms. That's all that happens - an exchange of a few atoms. Yet it's
enough to make people very ill. The effect of the change is to create a sticky point between on abnormal molecule and its
neighbor, causing molecules to pile up on each other.
Normal red cells shaped like discs can easily pass through the small blood vessels of the body. When hemoglobin molecules
stick together, the red cells that carry them get distorted so badly that they have difficulty getting through the narrow
passageways. Parts of the body are deprived of precious oxygen.
There are thousands upon thousands of ways that two molecules might bind. And for the moment, the complete mechanical and
structural story of sickling remains a mystery. But knowing where the problem begins, where the first change occurs on the
molecule, can be of help in finding a chemical method for reversing the process and helping to cure the first known molecular
disease.
