Acridinium esters mechanisms

Figure 2 illustrates the reaction mechanisms of acridinium ester label probes and alkaline phosphatase probes using dioxetane chemiluminescent detection. Table 2 summarizes approaches for labeling DNA. 

Fio. 23. Mechanism for the peroxide-induced chemiluminescence of acridinium esters. The di-oxetaneone is a postulated metastable intermediate. 

The mechanism for the protection remains unknown, although there is some speculation that the acridinium ester intercalates between the strands of the hybridized duplex, within which it remains impervious to hydrolysis (A16). The assay protocol involves a hybridization step, followed by hydrolysis between pH 7.5 and... 

In addition to their implication as reactive intermediates in bioluminescence, dioxetanones have been proposed as key intermediates in several chemiluminescent systems. Most notable are the chemiluminescent oxidation reaction of acridan esters [19] and the chemiluminescent reaction of the related acridinium salts [20] (Rauhut et al., 1965a McCapra et al., 1977). Both reactions are quite efficient at generating singlet excited states (pCE = 10% and 2% respectively) and, owing to the elegant work of McCapra and others, are among the best understood complex chemiluminescent reaction mechanisms. 

Chemiluminescence generally arises from chemical reactions in solution in which an oxidation occurs that involves either molecular oxygen or hydrogen peroxide (H2O2). The quantum yield in solution is generally very low because certain derivatives inhibit luminescence, notably oxygen. There are some exceptions such as luminol, acridinium salts, and some oxalic esters. Although the mechanism is poorly understood, the reaction of luminol (5-amino-2,3-dihydro-l,4-phthalazinedione) can be written schematically ... 

The acridine nucleus has proved to be a good basis for a variety of chemiluminescent compounds. Among these are the acridinium active esters which not only provide the best understood examples of chemiluminescence to date but are of considerable value in determining the mechanism of light emission in certain bioluminescent organisms. 

Acridinium phenyl esters have been thoroughly investigated [14,19,22] with the convincing mechanism shown below as a result ... 

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