Elution times and UV absorption spectra of inosine, adenosine, and guanosine nucleotides in the diode array HPLC system used for the current experiments. The optical absorbance at 250- and 259-nm wavelengths is reported as a function of elution time. The nucleotides were dissolved in medium A, at concentrations within the ranges shown on the x axis of Fig. 2, to match those extracted from the RBC samples. Typical spectra obtained for each of the three types of nucleotides tested in this run are shown at the top of the figure. Results are typical of 13 similar experiments with different nucleotide additions.