Blue-fluorescing pterin

Fig. 6.1.1 The chemical structure of the most common blue-fluorescing pterins, including lumazin...

HPLC Gradient System with Column Switching for Blue-Fluorescing Pterins... 

Table 6.1.3 Gradient program used to control the HPLC gradient system with column switching for blue-fluorescing pterins ... 

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. 

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... 

The absorption band at 384 nm is composed of contributions of the radical species and the second chromophore, whereas the fluorescence spectra with excitation maxima at 398 nm and emission maxima at 470-480 nm are attributed to the pterin alone (146, 155). The 7,8-dihydropterin cofactor, Xmax = 360 nm when free in solution and 390 nm when protein bound, is labile at neutral pH, readily decomposing upon denaturation to form products without significant visible absorption maxima. The photoreduction described above also reduces the second cofactor but in an irreversible manner with complete loss of its fluorescence and visible absorption characteristics (157). Reduction of the blue semiquinone FAD cofactor to the fully reduced form has no effect on the absorption spectrum of the pterin, suggesting that the absorption spectrum of the second cofactor must be independent of the oxidation state of the flavin and that the two cofactors are electronically isolated from each other (157). However, reduction of the flavin radical results in an increase in the fluorescence of the second cofactor, possibly indicating that the flavin radical acts as a potent quencher of fluorescence of the 7,8-dihydropterin. 

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