Crystal structure and growth behavior of aspartame form I-A.
H.M. Cuppen, G. Beurskens, S. Kozuka, K. Tsukamoto, J.M.M. Smits, R. de Gelder, R.P.F. Grimbergen, H. Meekes
CRYSTAL GROWTH & DESIGN 2005, 5, 3, 917-923

Abstract:
The structure, morphology, and growth behavior of aspartame form I-A are presented. This form can be obtained from a purely aqueous solution and is the form with the highest industrial importance. The aspartame molecules are arranged around large hydrophilic channels filled with water molecules. The crystal morphology of this compound is needlelike with polar growth behavior in the needle direction. The side faces show a large nucleation barrier for growth, whereas the top faces possess a much smaller barrier. Monte Carlo simulations are performed for this crystal structure, and the resulting growth rate, morphology, and polarity are all in agreement with the experimental observations.