Models validation in QSAR, pharmacophore, docking, and others, can ensure the accuracy and reliability of future predictions in design and selection of molecules with biological activity. In these study, the caffeine molecule was optimized using Hartree-Fock (HF) and Density Functional Theory (DFT/B3LYP) methods, with seven basis sets. Linear correlation data, errors and RMSD values between theoretical and experimental data allowed us to classify the methods and basis sets for evaluating their correspondence with experimental data (geometric parameters, heat capacity, as well as Infrared, Raman and NMR spectra). The HF method has shown the highest correspondence with the experimental data, occupying the top-five rank of the general classification. The HF/6-31G** method was the best one classified and it can be used to model the biological activity of the caffeine molecule.

Chagas disease (CD) causes the highest burden of parasitic diseases in the Western Hemisphere and is therefore a priority for drug research and development. Platelet-activating factor (PAF) causes the CD parasite Trypanosoma cruzi to differentiate, which suggests that the parasite may express PAF receptors. Here, we explored the T. cruzi proteome for PAF receptor-like proteins. From a total of 23,000 protein sequences, we identified 29 hypothetical proteins that are predicted to have seven transmembrane domains (TMDs), which is the main characteristic of the G protein-coupled receptors (GPCRs), including the PAF receptor. The TMDs of these sequences were independently aligned with domains from 25 animal PAF receptors and the sequences were analysed for conserved residues. The conservation score mean values for the TMDs of the hypothetical proteins ranged from 31.7-44.1%, which suggests that if the putative T. cruzi PAF receptor is among the sequences identified, the TMDs are not highly conserved. These results suggest that T. cruzi contains several GPCR-like proteins and that one of these GPCRs may be a PAF receptor. Future studies may further validate the PAF receptor as a target for CD chemotherapy.