Approaching an experimental electron density model of the biologically active trans ‐epoxysuccinyl amide group—Substituent effects vs. crystal packing

Similarities and Differences between Crystal and Enzyme Environmental Effects on the Electron Density of Drug Molecules

The crystal interaction density is generally assumed to be a suitable measure of the polarization of a low-molecular weight ligand inside an enzyme, but this approximation has seldomly been tested and has never been quantified before. In this study, we compare the crystal interaction density and the interaction electrostatic potential for a model compound of loxistatin acid (E64c) with those inside cathepsin B, in solution, and in vacuum. We apply QM/MM calculations and experimental quantum crystallography to show that the crystal interaction density is indeed very similar to the enzyme interaction density. Less than 0.1 e are shifted between these two environments in total. However, this difference has non-negligible consequences for derived properties.

Quantifying intermolecular interactions for isoindole derivatives: substituent effect vs. crystal packing

The aim of the study was to examine noncovalent interactions in considerably different crystal packings of three isoindole compounds. Their structures were compared to three other closely-related derivatives described earlier in the literature. Here we discuss the crystal structures in the context of the hydrogen-bonded motifs and other weak interactions. The hierarchy of investigated intermolecular interactions was examined in a quantitative manner through pairwise interaction energies and energy framework analysis.