Magnetic circular dichroism of adenine, hypoxanthine, and guanosine 5′‐diphosphate to 180 nm

The magnetic circular dichroism (MCD) of adenine, hypoxanthine, and guanosine 5′‐diphosphate reveals that, for each species, the uv‐absorption band near 200 nm is composed of at least two electronic transitions. The theory of MCD shows that the dipoles of these transitions are not parallel to one another. The transitions are assigned within the framework of current theories of the electronic structure of the purines. Knowledge of the presence of more than one transition within an absorption envelope is important in interpreting the corresponding natural CD of DNA and RNA.