Oxidation long-wave

Finally, the polyamide oxidative fluorescence is unmistakably quenched when the fluorescing plate is treated with sodium meth-oxide or IN sodium hydroxide, dried, and viewed under long-wave UV light, a test developed by Malshet, et al. (27). Methanol or water alone has no effect. Strong acid restores the fluorescence. We were not able to quantitate this quenching and restoration, because of the risk of damage to the solid sample holder. 

The prepared compounds systematically differed in the distance of the dihydropyridine and the flavin recognition part. Binding between flavin and the NADH model systems was proved by potentiometric pH titrations. Redox reaction between the NADH model systems and flavin was monitored by UV - VIS spectroscopy. The intensity of the long-wave absorption of flavin at 456 nm significantly decreased during the reaction and the decrease was attributed to the reduction of flavin to the fully reduced flavohydroquinone. At the same time, the intensity of the peak around 360 nm decreased as well, because of the reduction of flavin and the concerted oxidation of the 1,4-dihydronicotinamide to the corresponding pyridinium species. Kinetics of the electron transfer was studied and two reasonable kinetic models were proposed. 

It follows from the experimental data that the distribution function of SC is bimodal. The fraction with shorter wavelengths in the optical absorption spectrum is characterized by less pronounced spectral difference between SC in this fraction than that for long-wave SC. The decomposition of the optical absorption spectrum of SC into two fractions and a change in its shape (calculated in this approximation) during oxidation are shown in Figure 7.23b and c, respectively. A satisfactory agreement between the experimental and calculated dependences is observed. The difference in the properties of SCs is certainly associated with their spatial structure however, it remains unclear what structural features of quartz glass are responsible for the stabilization of two types of sites. 

Independent support for interflavin o-contacts comes from recent chemical studies by Favaudon and Lhoste (13,14). The french authors describe, as already anticipated, a nearby diffusion-controlled dimer formation in aprotic polar medium as the first step in the interflavin contact between oxidized and reduced states, which would finally yield two flavin radicals. This dimer was shown to be not identical in any respect with the well known quinhydrone which can only be obtained in aqueous systems at high flavin concentrations. The long wave band in the absorption spectrum of the new dimer appears to be of charge transfer type, but with a highly reduced half width and better resolved shape than the flavoquinhydrone spectrum. 

Klnetlcally, long-wave oxidation after the induction period, may be represented by the expression. 

Nitrous oxide (N20), another greenhouse gas, is stable in the troposphere, but oxidizes to ozone-reactive NO in the stratosphere. Molecule for molecule, N20 is currently about 200 times more effective in absorbing long-wave infrared radiation than is carbon dioxide, and its atmospheric concentration... 

L.M. Postnikov, IN. Smolenskiy, E.V. Viehutinskaya, I S. Lukomskaya, New mechanism of long-wave oxidation of polyamides////en[Pg.162]

The width Eg of the forbidden band (i.e the band gap) of a semiconductor serves as the threshold energy that determines the red, i.e. long-wave, boundary Xo, of the optical absorption spectrum of the material. This parameter is very important to the photocatalytic properties of a semiconductor particle. Eg data for some oxides that are present in the atmosphere, are given in Table 2. 

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