Suntan aids
Products give a person the appearance of a suntan without the person having to spend hours in the sun have become very popular in recent years. These products contain dihydroxyacetone HO-CH2-CO-CH2OH,C3H6O3) as active ingredient . notice that this fits our definition of a carbohydrate (chapter 17) and is half the molecular formula of glucose. Sugars react with amines to give brown products called melanoidins. In this case,the part of the sugar that reacts is the oxygen that is double-bonded to the central carbon and the amine is the nitrogen atom on the side chain of the three amino acids arginine ,lysine,and his-tidine.these are fairly abundant in the protein of the outer layer of human skin. Melanoidins are large,cross-linked molecules which are quite stable so the sunless tan lasts quite a while.