CHARACTERIZATION OF L-ISOLEUCINE CRYSTAL MORPHOLOGY FROM MOLECULAR MODELING

An accurate prediction of the L-isoleucine crystal morphology is demon strated through the application of a molecular mechanics simulation us ing a suitable force field. The model prediction is validated against crystals grown by several experimental methods and in multiple environ ments. Semiempirical quantum chemistry techniques were required for de termination of the electronic structure of the isoleucine molecules. S table simulated crystal morphologies were obtained upon application of the point atomic charges from these techniques. Additionally, no expl icit hydrogen bonding energy term was needed for energy minimization o r morphology prediction of the amino acid crystal when using these ato mic charges. The significant nonbonded energy within the crystal deman ded morphology calculation procedures that considered these contributi ons to the crystal lattice energy. Attachment energy morphology calcul ations performed on the potential energy minimized model using the gen eric DREIDING2.21 force field and developed minimization protocol with the derived partial charges ultimately proved successful in simulatin g the macroscopic L-isoleucine crystal shape. (C) 1998 Elsevier Scienc e B.V. All rights reserved.