Electronic structure and biological activity of nucleobases.

HeI and HeII photoelectron spectra of 6-chloro-1,3-dimethyluracil have been measured. The assignment of the spectrum was made by comparison with photoelectron spectra of related compounds and by high-level OVGF calculations. The electronic structure changes in substituted nucleobases are discussed on the basis of photoelectron spectroscopic data. The electronic structure data are compared with structure-activity relationships regarding enzyme inhibition and complex formation. The electronic structure data give some insight into the nature of binding between nucleobases' derivatives and different enzymes whose activity they inhibit.