Fluorescence spectra browning

In spite of the robust evidence in favor of ascorbic acid working to the benefit of the lens and the prevention of cataract, there is also considerable evidence to the contrary. Bensch and coworkers (1985) point out that when bovine lens crystallins are incubated for a prolonged period with physiological concentrations of ascorbic acid, a yellowish brown color develops. The fluorescence spectrum of this color was found to match that of proteins in lenses with senile nuclear cataract, leading the authors to speculate that nonenzymatic reactions of lens crystallins with ascorbic acid could contribute to the deterioration of the lens. Ortwerth and colleagues have... 

Figure 11. Polyamide fluorescence emission spectrum from fructose-amine browning (excitation wavelength, 360 nm). Condition Fructose 0.2 M, 80 °C.

Fig. 9.62 a Fluorescence spectra (345 nm excitation) of the oFL reference (pink spectrum), 24a (iorange spectrum) and 24b (brown spectrum) in toluene representing the quenching of the oFL emission, b Fluorescence spectra of the C60 reference (black spectrum), 24a (orange spectrum) and 24b (brown spectrum) in toluene representing the quenching of the C60 emission... 

Macroscopic Characteristics. In white light, the scorches and bums vary from a light brown shading into a darker brown and finally into black. As indicated previously, the light scorch marks resemble the body-only image in the visible spectrum (4), but not under fluorescence (10). 

Orange crystals from acetic acid, mp 200-203 (Org. Syn.. Orange plates from ether. Deep red needles from alcohol, benzene, toluene, xylene, mp 196. Sublimes in high vacuum. Absorption spectrum Meek, Watson, J. Chem. Soc. 1 9,544 (1916) Meek, Ibid 111,969 (1917). K at 18" = 3.1 x 10-,°. Moderately sol in alcohol with red color. Sol in ether with brown color and yellow fluorescence. Sol with violet color in aq alkalies and in ammonia. Black precipitate with CO,. One gram dissolves in about 13 g of boiling glacial acetic acid. 

The colour of the irradiated layer changes from green to brown, which suggests loss of iodine. The % loss in mass was 22.0%. The peaks in the electronic spectrum of a solution in acetonitrile did not rqipear after heating. Under prolonged irradiation, a yellow substance speared at the edges. This substance the original complex and Agl produced, showed fluorescence under uv irradiation. 

Spectra of chloroplast membranes shown In Fig. 1 were Identical for either Mantonlella or Mloromonas. The red absorption peak of Chi h near 643 nm is over 5 nm lower than It appears In other green plants the band near 632 nm Is normally seen only in Chi -containing algae [Mann, Myers 1968] and here may be MgDVP the band near 520 an may be from mlcroxanthln. The fluorescence emission spectrum was also unusual In that there were no long wavelength maxima (>700 nm) [Brown, 1969] the absorption spectrum... 

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