Chemiluminescence singlet sensitized

It follows that singlet sensitized chemiluminescence is also possible. 

Li X, Zhang G, Ma H et al (2004) 4, 5-Dimethylthio-4 -[2-(9-anthryloxy)ethylthio]tetra-thiafulvalene, a highly selective and sensitive chemiluminescence probe for singlet oxygen. J Am Chem Soc 126 11543-11548... 

Emission from dimols of singlet oxygen may be detected by photomultipliers used for measurement of chemiluminescence from hydrocarbon polymers with a maximum spectral sensitivity at 460 nm. The above scheme, however, requires the presence of at least one molecule of hydrogen peroxide in close vicinity to the two recombining peroxyl radicals and assumes a large heterogeneity of the oxidation process. 

A spectro-radiometer-luminometer for chemiluminescence and fluorescence quantum yield studies has been described by B. G. Roberts and H. C. Hirt 187>. To obtain emission spectra from very weak chemiluminescence reactions, a large-aperture spectrograph combined with a sensitive image-intensifier tube has been used68 this was developed from a device previously constructed by Bass and Kessler 188>. With it, it was possible to record the very weak emission of singlet oxygen dimer... 

CL reactions are commonly divided into two classes. In the type I (direct) reaction the oxidant and reductant interact with rate constant kr to directly form the excited product whose excited singlet state decays with the first (or pseudofirst)-order rate constant ks = kf+ kd. In the type II (indirect) reaction the oxidant and reactant interact with the formation of an initially excited product (kr) followed by the formation of an excited secondary product, either by subsequent chemical reaction or by energy transfer, with rate constant kA. The secondary product then decays from the lowest excited singlet state with rate constant kt. Type II reactions are generally denoted as complex or sensitized chemiluminescence. 

Lipid hydroperoxides are also generated in singlet molecular oxygen mediated oxidations and by the action of enzymes such as lipoxygenases and cyclooxygenases. Chemiluminescence (CL) arising from lipid peroxidation has been used as a sensitive detector of oxidative stress both in vitro and in vivo . Several authors have attributed ultra-weak CL associated with lipid peroxidation to the radiative deactivation of O2 and to triplet-excited carbonyls (63, 72) (equations 35 and 36) " . It has been proposed that the latter emitters arise from the thermolysis of dioxetane intermediates (61, 62) (equation 35), endoperoxide (73) (equation 37) and annihilation of aUtoxyl, as well as peroxyl radicals ... 

Figure 8.14 Sensitized emission from suitable acceptor in chemiluminescence reaction between H4Oj-t-.OCl- generating singlet oxygen and singlet oxygen pair states.

Carbonyl compounds 12-15 most likely derive from the corresponding intermediate dioxetanes 20, which under the reaction conditions would be expected to decompose thermally and or by direct sensitized photolysis, usually through a chemiluminescent process due to the fluorescence emitted by the singlet electronically excited carbonyl compound [17-20] [Eq. (9)]. 

The electronic excited state is inherently unstable and can decay back to the ground state in various ways, some of which involve (re-)emission of a photon, which leads to luminescence phenomena (fluorescence, phosphorescence, and chemiluminescence) (22). Some biologic molecules are naturally fluorescent, and phosphorescence is a common property of many marine and other organisms. (Fluorescence is photon emission caused by an electronic transition to ground state from an excited singlet state and is usually quite rapid. Phosphorescence is a much longer-lived process that involves formally forbidden transitions from electronic triplet states of a molecule.) Fluorescence measurement techniques can be extremely sensitive, and the use of fluorescent probes or dyes is now widespread in biomolecular analysis. For example, the large increase in fluorescence... 

The dioxiranone intermediate, which is formed in small amounts, reacts with the sensitizer to give singlet atomic oxygen and carbon dioxide the reaction of the singlet oxygen with the sensitizer is responsible for the chemiluminescence [1946]. 

The chemiluminescence emission at 25-60° C was measured from films of cis-1,4-polybutadiene, 1,2-polybutadiene, and trans-polypentenamer. The polymers were autoxidized previously in air 100°C, or allowed to react with singlet molecular oxygen in solution, and then cast into films. Values of ft (or kaCOz -> 302)/K(102 + polymer -> products)) were determined in benzene for cis-1,4-polybutadiene and cis-1,4-poly-isoprene, and for model compounds cis-3-hexene and cis-3-meihyl-3-hexene by independent methods. The chemiluminescence emission from irradiated films of the polymers containing a dye sensitizer showed a complicated time dependence, and the results depended on the length of irradiation. 

Chemiluminescence.—It has been suggested that problems which occur in the determination of yields of bio- and chemi-luminescence may be due to the sample cell. Errors of 25% may be caused by reflection and refraction from interfaces, and, consequently, frosted containers and point-source geometries were recommended. Several authors have concentrated on the use of sensitizers for the enhancement of chemiluminescence. The heavy-atom effect was found to operate in the energy transfer from enzyme-generated acetone to xanthene dyes. 9,10-Diphenylanthracene (9,10-DP A) has been suggested to be a poor singlet counter for chemiluminescence as some triplet states were also counted. In another report, 9,10-dibromoanthracene was found to be a more effective enhancer, when compared with 9,10-DPA, for chemiluminescence from a cyclic peroxide. Luminol chemiluminescence was employed in the analysis of Cr" ions in sea-water. Enhancement with bromide ions enabled detection limits of 3.3 X 10 m to be achieved. 

A novel sensitized chemiluminescence from thiazine dyes sensitized by singlet oxygen has been observed 807 and the absolute yields of chemiluminescence from the pulse radiolysis of aqueous dye solutions have been determined.808... 

Since the chemiluminescence is an assay for phagocytizing cells and Eq. (56) represents a singlet oxygen generating system it is possible to use the Lumlnol chemiluminescence reaction to enhance the (Eq. (A)) and therefore to increase the sensitivity of the assay. Trush et al. (1978) report a maximum chemiluminescent intensity of 3.3 x lO count s PMN from normal PMN measured in the liquid scintillation counter. 

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