Molecular basis of drug action of some antibiotics

A molecular model for the role of nucleoside or nucleotide analogs in drug action has been developed. This model, an extension of our earlier model has been employed to examine the possibility of incorporation of the formycin class of antibiotics (formycin, formycin B and oxoformycin B) in the growing RNA chain. Interaction energy of the analogous bases has been computed for the entire available space inside the deep groove of the DNA double helix. The values of the interaction energy thus computed along with the location of the sites of possible association are compared with the recommended configuration for RNA during transcription. It has been found that only formycin which structurally and energy-wise fulfils the requirement of the model, can successfully replace adenosine during transcription. Results are in agreement with experimental findings.