An amino acid residue (other than glycine) has no symmetry elements. The general operation of conversion of one residue of a single chain into a second residue equivalent to the first is accordingly a rotation about an axis accompanied by translation along the axis. Hence the only configurations for a chain compatible with our postulate of equivalence of the residues are helical configurations.

In teaching, you do not want to COVER things, you want to UNCOVER them. The best way to get good ideas is to have lots of ideas.

Nations keep agreements, keep their treaties so long as they continue to do them good.

You can't have good ideas unless you have lots of ideas.

Life ... is a relationship between molecules.

There is no safe amount of radiation. Even small amounts do harm.

It has been recognized that hydrogen bonds restrain protein molecules to their native configurations, and I believe that as the methods of structural chemistry are further applied to physiological problems it will be found that the significance of the hydrogen bond for physiology is greater than that of any other single structural feature.