Modelling of guanine-derivative--protein interaction complexes as a basis of drug design

In rational drug design the study of protein-ligand-interactions is one of the most important approaches to get knowledge of SAR. On this study N2-Phenylthioguanines were synthesized by Schiemann reaction from thioguanine followed by a substitution of the fluorine by aniline-derivatives. The activity of these HSV1 TK inhibitors was determined by kinetic measurements of thymidine phosphorylation. The N2-Phenylthioguanines gave the same activity as the oxoanalogues. Interaction energies between thymidine and HSV1 TK were measured by microcalorimetry. Results of the measurement showed negative delta G and delta H values which indicates that the binding of the natural substrate occurs spontaneously and is enthalpy driven.