Circular dichroism of some mononucleosides

The circular dichroism (CD) and absorption spectra of uridine, thymidine, purine ribonucleoside, and the four adenine derivatives 2′‐deoxyadenosine, adenosine, adenosine‐3′,5′‐cyclic phosphate, and arabinosyl adenine were measured in water at pH 7 and pH 2. The absorption and CD spectra of the pyrimidines were simultaneously fitted to four Gaussian bands, and the dipole and rotational strengths of the electronic transitions determined. Adenine‐derivative CD spectra were determined by computer averaging six runs. The spectra showed CD bands at 268, 226, 209, and 195 nm. The band at 226 nm probably is an n–π* transition; the band at 209 nm cannot be detected without a computer. The CD and absorption spectra of purine ribonucleoside indicate three transitions in the 230–310‐nm region.