PURINES AND PTERIDINES FROM THE REFLECTING PIGMENT OF THE ARTHROPOD RETINA

¹ The Biological Laboratories, Reed College, Portland, Oregon; and Marine Biological Laboratory Woods Hole, Mass.

1. The chemical nature of the retinal reflecting pigment was studied in Homarus and in Limulus. In crustaceans the reflecting pigment has been thought to be guanine, but the solubility and chemical properties of this pigment from Homarus do not agree with those for guanine.

2. Use of paper chromatographic methods shows the presence of five substances in the reflecting pigment of Homarus, three of which are absorbent or quenching in ultraviolet light and two of which are fluorescent.

3. Histochemical treatment with methenamine-silver and incubation studies with uricase identify one of the three ultraviolet-absorbent compounds as uric acid. Comparisons of R_f indices of the other two ultraviolet-absorbent compounds with those of reference purines show them to be xanthine and hypoxanthine. Identifications of all three were verified by determining the ultraviolet absorption spectra of the retinal purines eluted from paper chromatograms.

4. One of the two fluorescent components of Homarus reflecting pigments is xanthopterin, identified both by its R_f indices after chromatographic development in a variety of solvent systems, and by its absorption spectrum. The second fluorescent compound, probably a pteridine, has not been identified, but its absorption spectrum shows maxima at 245 mµ and 353 mµ in 0.1 N HCl; in alkali these maxima are shifted to 255 mµ and 390 mµ.

5. Retinal reflecting pigment from Limulus is guanine.