Ultraviolet radiation absorbers

Using QMOBAS, TMOBAS, or Mathcad and the method from Computer Project 6-2, calculate the energy separation between the HOMO and LUMO in units of p for all compounds in Table 6-1 and enter the results in Table 6-2. Enter the observed energy of ultraviolet radiation absorbed for each compound in units of cm . The reciprocal wavelength is often used as a spectroscopic unit of energy. 

Nardi and Yatsiv (141) studied the temperature dependence and the decay times of europium emissions in europium dibenzoylmethide. In this compound the ultraviolet radiation absorbed by the organic component is transferred to the rare-earth ion and fluorescence is emitted from two levels, namely, the SD0 and the 5DI. The compound was prepared by treating a solution of EuC13 in ethanol with a solution of dibenzoylmethane in ethanol. The compound was precipitated by the addition of piperidine. 

Ultraviolet radiation absorbed by Ti02 creates an electron-hole pair. The hole oxidizes H20 to the powerful oxidant HO The electron reduces 02 to H20 by a chain of reactions. Ti02 is a catalyst and 02 is consumed in the net reaction organic C + 02 — C02. 

This synthesis of ozone is of great benefit to life on Earth because if the ultraviolet radiation absorbed in the reaction were to reach Earths surface, it would cause immediate harm to living tissue. When it absorbs ultraviolet radiation, ozone fragments into molecular oxygen and atomic oxygen. These molecules eventually re-form ozone. Because chemical bonds are created when ozone reforms, heat energy is released ... 

The most obvious fluorescent compound in milk is riboflavin, which absorbs strongly at 440-500 nm and emits fluorescent radiation with a maximum at 530 nm. Riboflavin in whey is measured easily by fluorescence (Amer. Assoc. Vitamin Chemists 1951). Proteins also fluoresce because of their content of aromatic amino acids. Part of the ultraviolet radiation absorbed at 280 nm is emitted at longer wavelengths as fluorescent radiation. A prominent maximum near 340 nm is attributable to tryptophan residues in the protein. Use of fluorescence for quantitation of milk proteins was proposed by Konev and Kozunin (1961), and the technique has been modified and evaluated by several groups (Bakalor 1965 Fox et al. 1963 Koops and Wijnand 1961 Porter 1965). It seems to be somewhat less accurate than desired because of difficulties in disaggregating the caseinate particles and in standardizing instruments. It also involves a basic uncertainty due to natural variations in the proportions of individual proteins which differ in tryptophan content. 

Dunlap, W. C. and Shick, J. M., Ultraviolet radiation-absorbing mycosporine-like amino acids in coral reef organisms a biochemical and environmental perspective, J. Phycol., 34, 418, 1998. 

Teai, T., Drollet, J. H., Bianchini, J. P., Cambon, A., and Martin, P. M. V., Occurrence of ultraviolet radiation-absorbing mycosporine-like amino acids in coral mucus and whole corals of French Polynesia, Mar. Freshwater Res., 49, 127, 1998. 

Lappin, G. R., "Ultraviolet-Radiation Absorbers, Encycl. Polym. Science... 

J.M. Shick, W.C. Dunlap, B.E. Chalker, A.T. Banaszak, T.K. Rosenzweig (1992). Survey of ultraviolet radiation-absorbing mycosporine-like amino acids in organs of coral reef holothuroids. Mar. Ecol Prog. Ser., 90,139-148. 

J.P. Zamzow, G.S. Losey. Ultraviolet radiation absorbance by coral reef fish mucus photo-protection and visual communication. Environ. Biol Fish, 63,41-47. 

The development of chemistry has depended strongly upon careful measurements. Historically, measurements of the quantities of substances reacting and produced in chemical reactions have allowed the explanation of the fundamental nature of chemistry. Exact measurements continue to be of the utmost importance in chemistry, and are facilitated by increasingly more sophisticated instrumentation. For example, atmospheric chemists can determine a small degree of stratospheric ozone depletion by measuring minute amounts of ultraviolet radiation absorbed by ozone with satellite-mounted instruments. Determinations of a part per trillion or less of a toxic substance in water may serve to trace the source of a hazardous pollutant. This section discusses the basic measurements commonly made in chemistry and environmental chemistry. 

Mason DS, Schafer F, Shick JM, Dunlap WC. 1998. Ultraviolet radiation-absorbing mycosporine-like amino acids (MAAs) are acquired from their diet by medaka fish Oryzias latipes) but not by SKH-1 hairless mice. Comparative Biochemistry and Physiology 120 587-598. 

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