Electronic Supplementary Information Theoretical Analysis of Intermolecular Interactions of Selected Residues of Triosephosphate Isomerase from Trypanosoma cruzi with its Inhibitor 3-(2-Benzothiazolylthio)-1-propanesulfonic Acid

The use of the MP2 aproximation with a small basis set is known to reproduce interaction energies for weakly bonded complexes with fairly good accuracy, when corrected for the BSSE. However, it is always a good practice to compare the results obtained in this fashion with higher-level calculations whenever they are computationally allowable. In the case of the BTT-aminoacid complexes studied in the accompanying paper, the extrapolation of the MP2 energies to the complete basis set limit (MP2/CBS) was performed as a benchmark. As shown in Table S-1, the MP2/CBS results are very similar to those obtained at the MP2/6-31++G** level. For a qualitative comparison, Figure S-1 shows the dissociation curves for the complexes of BTT with phe75A, tyr102B and arg71A obtained with the two methods which give the same description within chemical accuracy. However, the nonextrapolated approach is preferred in our work because it provides, besides the energetics of the molecular association, a description of the electron density that can be used for further analysis.