Computational Modeling of the Molecular Complex Formed by DIPAIN II and T-2 Toxin

A fluorescence enhancement in the visible range under UV excitation has been observed in 2-(diphenylacetyl)-1,3-indanedione-l-(p-(dimethylamino)benzaldazine) (DIPAIN) II and its derivatives when associating with trichothecene mycotoxins on the solid support. Chromatographic study has shown that it is the molecular complex formed by weak association between DIPAIN II and 12,13-epoxytrichothec-9-ene-3,4,8,15-tetraol 4,15-diacetate 8-(3-methylbutanoate) (T-2) toxin that is directly related to the enhanced fluorescence activity. Previously, a model was proposed by other group to predict a mechanism of the interaction between the molecules in the complex. In this model, five functional groups and regions of DIPAIN II were identified as possible interaction sites with the toxin compounds. More than one area could interact with the compound at the same time. Inspired by these ideas, three mixture conformations of DIPAIN II and T-2 toxin are generated and studied in this paper. The initial geometric structures of two molecules were constructed according to the published papers, and optimization was performed using the Hartree-Fock and the density functional theories followed by calculations of the excited-state energy. The optimization results indicate that there is no chemical bonding between DIPAIN II and T-2 toxin. Nonbonded interactions between T-2 toxin and DIPAIN II could be responsible for the fluorescence enhancement. This conclusion is in agreement with the prediction of the model. The excitation energies are consistent with the experiment results.