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Molecular oxygen analysis

In the luminescence reaction of firefly luciferin (Fig. 1.12), one oxygen atom of the product CO2 is derived from the molecular oxygen while the other originates from the carboxyl group of luciferin. In the chemiluminescence reaction of an analogue of firefly luciferin in DMSO in the presence of a base, the analysis of the product CO2 has supported the dioxetanone pathway (White et al., 1975). [Pg.19]

A similar system, but with a more hindered porphyrin (tetramesitylporphyrin = tetraphenylporphyrin bearing three methyl substituents in ortho and para positions on each phenyl group), was tested for P-carotene oxidation by molecular oxygen. This system was chosen to slow the oxidation process and thus make it possible to identify possible intermediates by HPLC-DAD-MS analysis. The system yielded the same product families as with lycopene, i.e., (Z)-isomers, epoxides, and P-apo-carotenals, together with new products tentatively attributed to diapocarotene-dials and 5,6- and/or 5,8-epoxides of P-apo-carotenals. The oxidation mechanism appeared more complex in this set-up. [Pg.187]

A recent stndy (13,27) describes the use of Co-Si-TUD-1 for the liquid-phase oxidation of cyclohexane. Several other metals were tested as well. TBHP (tert-butyl hydroperoxide) was used as an oxidant and the reactions were carried out at 70°C. Oxidation of cyclohexane was carried out using 20 ml of a mixture of cyclohexane, 35mol% TBHP and 1 g of chlorobenzene as internal standard, in combination with the catalyst (0.1 mmol of active metal pretreated overnight at 180°C). Identification of the products was carried out using GC-MS. The concentration of carboxylic side products was determined by GC analysis from separate samples after conversion into the respective methyl esters. Evolution and consumption of molecular oxygen was monitored volumetrically with an attached gas burette. All mass balances were 92% or better. [Pg.374]

Lophine emits yellow CL upon oxidation by molecular oxygen in alkaline solution. The oxidation is believed to produce a free radical [3], which is further oxidized to a hydroperoxide, which is the light-emitting species [4-6], A number of chemiluminescent derivatives of lophine have been synthesized and have been shown to exhibit varying efficiencies of CL. Lophine has been used in the analysis of metal ions such as Co2+ that catalyze the chemiluminescent reaction between it and hydrogen peroxide [7], It has also been used as a chemiluminescent indicator in titrimetry [8],... [Pg.106]

Calculation of enthalpies of formation from the enthalpies of combustion of reactants and products This method is generally applicable for any combustible material for which the gross molecular formula is known. The enthalpies of combustion may be determined in a calorimeter using excess oxygen. Analysis of the combustion products may be appropriate. [Pg.34]

It has been proposed that the metal ion also has an interaction with the pro-Rp oxygen atom at the scissile phosphate, Pi.i. However, the scissile phosphodiester bond, within the crystal structure, is located approximately 20 A from the A9/G10.1 site [96]. It should be true that a conformationd change occurs to rotate the initial structure that is not feasible for the inhne attack to in-line structure around the scissile phosphate, but molecular dynamics analysis denies to arrange A9/G10.1 to come close to Pi.i via a metal ion. Furthermore, although it has been suggested that there is a weak interaction of a metal ion with the oxygen atom at P 1.1, our recent experiments observed no interaction of a metal ion with the Pi.i phosphate by kinetic and NMR analyses [97, 98]. [Pg.228]


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See also in sourсe #XX -- [ Pg.94 , Pg.411 ]




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Analysis oxygen

Molecular analysis

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