Ultraviolet light, damages from

Paint coatings on wood provide the most protection because they block the damaging ultraviolet light rays from the sun. They may be either oil-based or latex-based. Either type is available in a wide range of colors. Oil or alkyd paints are borne by an organic solvent, whereas latex-based paints are water-borne. The three primary reasons for using paints are to protect the wood surface from weathering, to conceal certain defects, and for aesthetic purposes. 

Benzophenone is used to prevent ultraviolet light from damaging scents and colors in products such as perfumes and soaps. It allows the manufacturer to package the product in clear glass or plastic. Without it, opaque or dark packaging would be necessary. 

Figure 6.46 Representation of two mechanisms of repair of DNA damage such as ultraviolet light-induced dimerization. The upper line represents cut and patch repair, the lower sister-strand exchange. Thick lines represent newly synthesized DNA. Source From Ref. 12.

Direct Repair Several types of damage are repaired without removing a base or nucleotide. The best-characterized example is direct photoreactivation of cyclobutane pyrimidine dimers, a reaction promoted by DNA photolyases. Pyrimidine dimers result from an ultraviolet light-induced reaction, and photolyases use energy derived from absorbed light to reverse the dam-... 

Photolysis is carried out in an 850-ml. Pyrex glass vessel equipped with a water-cooled quartz probe. The ultraviolet light source is a 450-watt lamp with a Vycor filterf. To reduce the dangers from a possible explosion or eye damage from ultraviolet radiation, the reaction vessel shown in Fig. 5 is contained in a wooden box. 

Wei, H. et al., Scavenging of hydrogen peroxide and inhibition of ultraviolet light-induced oxidative DNA damage by aqueous extracts from green and black teas, Free Radio. Biol. Med., 26, 1427-1435, 1999. 

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