Chemiluminophors

Chemiluminescence immunoassay,a technique that has rapidly gained popularity because its sensitivity is comparable to that of radioimmunoassay, is in a sense a variation of FIA. In the 1930s, the first work on chemiluminophores was published, but it was not until the 1980s that chemiluminescence was first tried in immunoassays. Due to the increased use of automated immunoassay analyzers, chemiluminescence has become one of the most common immunoassay detection methods used in the clinical laboratory setting. Chemiluminescence (also called bioluminescence when it occurs in fireflies and some dinoflagellates, coelente-rates, and fungi) is fluorescence. However, what is... 

Okamoto H, Owari M, Kimura M, Satake, K. Preparation of a crown-ether-modified lophine peroxide as a guest-sensitive novel chemiluminophore and modulation of its chemiluminescence by metal cations. Tetrahedron Lett 2001 42 7453-5. 

GENERATION OF HIGH-ENERGY CHEMILUMINOPHORES IN AMBIENT LIGHT... 

The material presented herein encompasses the energy accumulation in organic processes through the formation of high-energy chemiluminophores (X in Scheme 1), the latter species are furnished by intermediate dioxetanes and pertinent photoisomers and photodimers. 

Generation of High-Energy Chemiluminophores in Ambient Light 149... 

The interaction of both Rg and Rg isomers with bases is exothermic however, the energy released in the reaction of Rg with HO is not sufficient for the electronic excitation of the hydrazone anion, the chemiluminescence emitter. The PM3 computations reveal that the enthalpy of the Rg formation exceeds that of the Rg species by 130 kJ/mol, which covers the energy deficiency for the excitation of the light emitter. Thus, the Rg species constitutes the putative high-energy chemiluminophore, which is readily generated in the ambient light. 

Luminol can be used to derivatize analytes (for immunoassay or HPLC) through substitution at the primary amine but this results in a 10- to 100-fold decrease in chemiluminescence efficiency. Isoluminol (6-amino-2,3-dihydro-l,4-phthalazinedi-one) is somewhat less efficient than luminol however, it does not suffer a decrease in efficiency upon binding. Aminobutylethylisoluminol (ABEI, (9) is a useful precolumn labeling reagent for amines and carboxylic acids because the hydrocarbon spacer isolates the chemiluminophore from the analyte. 

Further enhancement in detection sensitivity of reporter enzymes is achievable by enzyme amplification or cascade reactions often termed enzyme cycling assays. One approach is to use alkaline phosphatase as the reporter enzyme. Phosphatase cleavage of NADP forms NAD, which enters cyclic reactions catalyzed by alcohol dehydrogenase and diaphorase. Each turnover of phosphatase substrate initiates a cascade resulting in numerous detectable product molecules. Such approaches, perhaps incorporating chemiluminophores as the terminal product, hold promise for further extension of the sensitivity of immunoenzymatic methods. 

Dioxetane and 1,2-dioxetanone are key chemical structures in many chemiluminescent and bioluminescent systems. The molecular structure of these systems bears the chemiluminophore properties of the chemi/bioluminescent molecules based on them, providing a channel for a thermally activated chemical reaction that produces a compound in an electronically excited state.The efficiency of the chemiluminescent process in 1,2-dioxetane and dioxetanone is however low and requires an electron-donor group to increase the quantum yield of luminescence. In addition, it is observed experimentally that the triplet emission is significantly more favourable than singlet emission in these small systems. From a theoretical standpoint, the general aspects of the... 

Li et and Chen et studied the bioluminescence of coe-lenterazine. Whereas the former work focused only on the absorption and emission properties of the product of the reaction (coelenteramide), the latter study also analysed relevant aspects of the mechanism, particularly, the origin and differences among chemiluminescence, bioluminescence and fluorescence in aequorin. On the basis of the TDDFT/ MM findings and the previous CASPT2 results on a small model and TDDFT results of the chemiluminophore in vacuo,the proposed mechanism (Fig. 12) has the characteristics described in the following ... 

---