Absorption spectra of the common nucleotides. The plots show molar extinction coefficients at pH 7.0 as a function of wavelength for the nucleoside 5’-monophosphates. The molar extinction coefficient, ε (epsilon; units m−1cm−1), measures the amount of light absorbed by a 1 m solution with a light path length of 1 cm. The table shows the molar extinction coefficients at 260 nm for the plotted nucleotides.