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Schistosomiasis is an infectious disease caused by parasitic worms. Large doses are necessary to achieve adequate concentrations at the destination due to low solubility of praziquantel. We use Monte Carlo simulations to generate structures of the water that will act as a solvent around praziquantel molecule with aim to study the formation of the solvation shells of the molecule after complexation into cyclodextrin. In this work it had shown an increased of the water number around praziquantel/ -cyclodextrin complexes in relation isolated praziquantel molecule. This increase of the water number is due to hydrophilic effect of the cyclodextrin molecule.

The analysis of amino acid fragmentation is promising in the search for living organisms in other planets, which could be investigated by just scanning for specific amino acid fragments in their upper atmosphere using advanced spectroscopy techniques. Motivated by this possibility, we develop here a Density Functional Theory (DFT)‐based protocol to investigate the fragmentation of an essential constituent of cells: the L‐cysteine amino acid. After determining the structural and energetics for neutral and single ionized conformers in good agreement with data available, we propose a novel protocol based upon the analysis of Wiberg bond order indices and Bader's Quantum Theory of Atoms in Molecules (QTAIM) theory. Our results indicate that the alpha carbon is the most favorable point of fragmentation for the CH2SH and COOH radicals after a cysteine molecule single ionization.

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The possibility of finding the fragmentation routes by theoretical methods, led us to compare the molecular ions between neutral molecules of benzene, aniline, and o-, m-, and p-nitroaniline, using the Density Functional Theory (DFT), under an aug-cc-pVDZ base set and a B3LYP exchange-correlation functional. After determining the structure and electronic energy of neutral and doubly ionized species, we used a new protocol based on the analysis of Wiberg's binding indexes and the quantum theory of atoms in Bader molecules (QTAIM). Where the charge transfer and electronic distribution in aromatic monomers indicate the possibility of fragment formation in at least two pairs of carbon-carbon (CC) atoms and indicate the possible loss of the -CNH2 and -NO2 groups in the aniline and nitroaniline molecules doubly ionized.