Luciferins 5,5-dimethyl

Chemiluminescence is also obtained by anionic autooxidation of (41) with oxygen ia alkaline dimethyl sulfoxide (DMSO) (216). Qc has been reported to be 10% and ketone (43) and CO2 are obtained. Several analogues of luciferin have been prepared that are also chemiluminescent when they react with oxygen ia alkaline DMSO (62). 

The yellow-green chemiluminescence of firefly luciferin is evidently dependent on the enol form of the thiazolinone 109a, for 5.5-dimethyl-luciferin 116a which does not yield an enolizable ketone does not exhibit a yellow-greenish emission on addition of excess base only red emission is observed. 

Wada N, Sameshima K. Ab initio calculation for D-(-)-luciferin and its intermediates in dimethyl sulfoxide. Bioluminescence Chemiluminescence, Proceedings of the International Symposium, 11th, 2001 Singapore World Scientific Publishing Co. Ltd., 251-4. 

Firefly luciferase catalyzes oxidation of luciferin with oxygen in the presence of MgATP. Luciferin (substrate) and oxyluciferin (reaction product) are molecules with pronounced fluorescent properties, therefore, fluorescent methods are widely used to study interactions of luciferase with the substrate, the product, and their analogs. Oxyluciferin is extremely unstable in aqueous solutions, however, one may expect that oxyluciferin analogs, dimethyl oxyluciferin (DMOL) and monomethyl oxyluciferin (MMOL), are more stable. Previously we have studied spectral and fluorescence properties of DMOL in aqueous solutions and it was shown that DMOL at alkaline pH undergoes decomposition to form a product with abs = 350 nm and Xem = 500 nm. The goal of this work was to study absorption and fluorescence spectra of MMOL and stability of MMOL and DMOL in aqueous solutions, and in the complexes with the wild-type and mutant (His433Tyr)... 

THEORETICAL ANALYSIS ON THE ABSORPTION SPECTRA OF INTERMEDIATES OF FIREFLY LUCIFERIN IN DEOXYGENATED DIMETHYL SULFOXIDE... 

Shibata R, Yoshida Y, Wada N. Filter-photometry of chemiluminescence from firefly luciferin intermediate M420 in deoxygenated dimethyl sulfoxide. J Photosci 2002 9 290-2. 

Firefly luciferin (111 R = R = H, X = OH) and a number of its analogues were synthesized by previously established reaction sequences from a variety of substituted 2-cyanobenzothiazoles (109) and cysteines (110). Amongst others, homoluciferin (112) and 5, 7 -dimethyl-luciferin (113) are accessible in this way. Their adenylates were produced by the condensation of the free acids with adenosine monophosphate in the presence of dicyclohexylcarbodi-imide. These were used in detailed spec-trophotometric studies of their chemiluminescence (initiated by bases), their fluorescence, and their bioluminescence under the influence of luciferase the possible mechanisms of these processes were discussed. ... 

The reaction has fairly strict solvent limitations. Polar aprotic solvents are required, the most usual being the dialkyl phthalates and ethylene glycol dimethyl ether. Other esters are also useful, but acetone, ethanol and halogenated hydrocarbons are much less effective. Some admixture of tert. butanol (up to about 5%) has little effect, but water and other alcohols reduce the quantum yield. It is interesting that the active site of firefly luciferase is known to be particularly hydrophobic. The mechanisms of the two reactions are rather similar in that both require a highly active ester (the adenylate in the case of the firefly). Attack by peroxide occurs in both cases (m mmolecular in the luciferin) and this process may require a non-aqueous environment for maximum efficiency. Some of the most efficient oxalates are listed in Table 2. 

---