MOLECULAR-MODELS FOR THE STEREOCHEMICAL STRUCTURES OF FUMONISIN B-1 AND B-2

Assessment of the structural configuration of fumonisin B-1 (FB1) and B-2 (FB2) would allow better understanding of the behavior of these mo lecules during isolation or other handling procedures, and their inter action with binding sites or antibodies. Molecular models of the absol ute configurations of FB1 and FB2 were calculated using a CAChe WorkSy stem(TM). The electrostatic potential energy surfaces of the minimum p otential energy conformations for FB1 and FB2 also were obtained. The models reveal that the backbone and acid side chains for FB1 and FB2 f orm a spherical globular model. The folded region forms a cage-like fe ature. It is this feature that suggests that these molecules may be po tential chelators. The electrostatic potential surfaces show that most of the exposed surfaces of these molecules are hydrophobic in nature, and that there is a distinct difference between the electrostatic pot ential surfaces of the FB1 models resulting from the stereochemistry p roposed by Shier et al. (1995) and Boyle and Kishi (1995a). The electr ostatic surfaces clearly show a different orientation of the hydrophob ic tail region of the backbone for FB2 than in the models for FB1.