Experimental evidence leading to an alternative explanation of why D-tyrosine sometimes crystallizes faster than its L-enantiomer.

On the occasions when D-tyrosine is observed to crystallize faster than its L-enantiomer, it is the result of a diastereomeric interaction between an airborne, non-racemic, chiral influence--probably a fungal spore--and the tyrosine enantiomers, enhancing the degree of crystal nucleation of D-tyrosine over L-tyrosine. This explanation, supported by experimental evidence, is presented as a more plausible alternative to the Shinitzky-Deamer hypothesis (Shinitzky et al., Progress in biological chirality, Elsevier, Amsterdam, pp. 329-337, 2004; Deamer et al., Chirality, 19:751-763, 2007) which relies on the parity violation energy difference between enantiomers, a femtojoule to picojoule per mole theoretical energy range.