Comments in a discussion: differential rates of D- and L-tyrosine crystallization.

We earlier reported that we had observed quantifiable differences in crystallization rates of D and L tyrosine. It has been suggested that these results were due to the presence of impurities. Here we argue that it is premature to conclude that impurities entirely explain the results. More generally, there is an accumulating weight of evidence that D and L enantiomers display unexpected differences in their physical properties and behavior. These should be taken into account as we attempt to understand the origin of biochirality.