I just came across this in the Editor’s Choice section of Science magazine (Oct 2, 2009, p. 19):
Getting a Grip on Nitrogen
Chirality is associated more with carbon than with nitrogen centers, as the latter atoms tend to invert their configurations fairly rapidly on account of their unbonded electron pair. Recently, relatively slow nitrogen inversion was observed in cyclic oligomers of four or six … amino acids … on account of hydrogen bonding among the substituents. Mocquet et al. now show that swapping in a single analogous [amino acid] residue that is chiral at carbon disrupts the collective inversion mechanism and thereby dramatically stabilizes the chrial nitrogen conformations throughout the ring.
Notice how the “editor” misuses the word “conformation” when referring to nitrogen “configuration”? Oh well. Probably a physicist.