Luciferin absorption spectra

Fig. 1.4 Absorption spectrum of a spent luminescence solution of firefly luciferin containing luciferase-oxyluciferin after dialysis in 0.1 M potassium phosphate, pH 7.8. Replotted from the data of Gates and DeLuca, 1975, with permission from Elsevier.

Fig. 3.1.4 Bioluminescence spectrum of Cypridina luciferin catalyzed by Cypridina luciferase (A), the fluorescence excitation spectrum of oxyluciferin in the presence of luciferase (B), the fluorescence emission spectrum of the same solution as B (C), and the absorption spectrum of oxyluciferin (D). The fluorescence of oxyluciferin alone and luciferase alone are negligibly weak. Measurement conditions A, luciferin (lpg/ml) plus a trace amount of luciferase in 20 mM sodium phosphate buffer, pH 7.2, containing 0.2 M NaCl B and C, oxyluciferin (20 pM) plus luciferase (0.2mg/ml) in 20 mM sodium phosphate buffer, pH 7.2, containing 0.2 M NaCl D, oxyluciferin (41 pM) in 20 mM Tris-HCl buffer, pH 7.6, containing 0.2 M NaCl. All are at 20°C.

Oxyluciferin. During the luminescence reaction catalyzed by luciferase, luciferin is converted into a fluorescent compound, oxyluciferin, accompanied by the emission of greenish-blue light that spectrally matches the fluorescence of oxyluciferin (Fig. 7.2.6). The absorption spectrum of oxyluciferin is shown in Figs. 7.2.1 and 7.2.2. 

Fig. 7.2.7 Absorption spectrum of the violet compound produced by the treatment of Odontosyllis luciferin with arylsulfatase, in 50 mM acetate buffer, pH 5.05. From Trainor, 1979.

Fig. 8.4 Absorption spectrum of dinoflagellate luciferin, and the spectral changes caused by luminescence reaction after the addition of luciferase, in 0.2 M phosphate buffer, pH 6.3, containing 0.1 mM EDTA and BSA (O.lmg/ml) (Nakamura et al., 1989). Reproduced from Hastings, 1989, with permission from the American Chemical Society and John Wiley Sons Ltd.

The luciferin showed an absorption spectrum identical with that of the fluorescent substance F of euphausiid (Xmax 388 nm), and gave... 

Fig. 9.13 Absorption spectrum of one of the luciferin precursors of Mycena cit-ricolor in methanol (dash-dot line, A.max 369 nm). The absorption and fluorescence emission spectra of the decylamine-activation product of the same precursor in neutral aqueous solution (solid lines abs. Amax 372 nm and fl. Xmax 460 nm), and in ethanol (broken lines abs. Amax 375 nm and fl. Amax 522 nm). The chemiluminescence spectrum of the same activation product (dotted line, A.max 580 nm). The dotted line (7max 320 nm) is the absorption spectrum of M. citricolor natural luciferin reported by Kuwabara and Wassink (1966).

Tsuji, F. I. (1955). The absorption spectrum of reduced and oxidized Cypridina luciferin, isolated by a new method. Arch. Biochem. Biophys. 59 452-464. 

Fig. 2. Changes in absorption spectrum of purified luciferin cf Cypridina during autoxidation (a) without visible luminescence, and during the light-emitting oxidation...

Odontosyllis luciferin is colorless and shows an absorption maximum at about 330 nm in aqueous ethanol (Figs. 7.2.1 and 7.2.2), and it undergoes various spectrum changes upon spontaneous oxidation... 

When a methanolic solution of luciferin was left at -20° C in the presence of air, most of the luciferin was oxidized in three days, based on its 1H-NMR spectrum. The air oxidation product was purified by HPLC on a TSK DEAE-5PW column using 35% acetonitrile containing 85mM NaCl and 3mM NaHCC>3. The purified product in the HPLC eluent showed absorption maxima at 237nm... 

The emitting molecule, decarboxyketoludferin, has been isolated and synthesized. When it is excited photochemically by photon absorption in basic solution (pH > 7.5-8.0), it fluoresces, giving a fluorescence emission specfrum that is identical to the emission spectrum produced by the interaction of firefly luciferin and firefly luciferase. The emitting form of decarboxykefoluciferin has thus been identified as the enol dianion. In neutral or acidic solution, the emission spectrum of decarboxyketo-luciferin does not match the emission spectrum of the bioluminescent system. 

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