Yellow-fluorescing pterin

Chromatograms of a standard mixture of blue-fluorescing pterins are shown in Figs. 6.1.6 (isocratic) and 6.1.7a (column-switching). Figure 6.1.8 shows yellow-fluorescing pterins. 

Fig. 6.1.8a-c HPLC of the yellow-fluorescing pterins, a Standard mixture b control cerebrospinal fluid (CSF) c CSF sepiapterin reductase deficiency. HS -Hydroxyse-piapterin, S sepiapterin, X xanthopterin... 

Jacobson s found that an orange-yellow fluorescence, which he was able to localize in the argentaffin cells of the alimentary tract, was produced by certain pterines. These were related to the pterine substance, folic acid. 

Purines absorb only ultraviolet light and they contribute to structural colors (white and silver) in animals. Pterines are generally yellow, orange, or red pigments. Because they are amphoteric molecules, the absorption spectra depend on the pH and present three or two absorption maxima, usually one in the visible region. Sepiapterin has an absorption maximum at 340 nm in O.IM NaOH and at 410 nm in O.IM HCl." Leucopterin has three maxima 240, 285, and 340 nm. Xanthopterin has two 255 and 391 nm. Because they are conjugated with proteins, pterins show bathochromic shifts in vivo. They also present fluorescence when excited with UV light. 

Intimations of an active metabolic role came from a closer examination of insects pterins were also abundant in actively metabolizing tissues. Thus the yellow pterin in the female reproductive ducts and testes sheath of certain races of Drosophila seemed identical with the yellow pigment in the wild-t3q>e eyes (Graf et al., 1955) the tissues generally of Drosophila have a deep violet-blue fluorescence (Hadorn and Schwinck, 1956). Identification... 

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