Comparative characteristics of a tryptophan molecule in the gas phase and water

Abstract

The L and D isomers of the tryptophan (Trp) molecule and the (Trp)⁺ cation in the gas phase and water are calculated at the DFT level to reveal the effect of water considered in the dielectric continuum approximation on the electronic characteristics of the molecule. The distribution of effective atomic charges and bond lengths enables the prediction of the most probable parts of the chemical bond cleavage during the fragmentation of the molecule under the ionizing particle flux. These data are supplemented with a calculation of fragmentation energies. Zwitterionic structures characterized by the appearance of considerable dipole moments and a change in their orientation with respect to the ground state are distinguished among the possible isomeric forms in water.