Protection from the sun

Melanin - a high-molecular compound is a complex structure. Its colorize and protective functions ar largely out-of-pocket to the fact that it has unexpended electrons . The implement of fundamental law of melanin is non richly elucidated, but it is cognize that an important region is played by the amino window pane tyrosine and tyrosinase enzyme (Fig. 1) . It is synthesized in limited beat cells - melanocytes and regulates this bring hormonal dust , mostly pituitary body horm hotshots (know as melanocyte-stimulating hormone ) . Interacting with a protein hint , forming dark melanin grains ranging in size from 0.1 to 2 microns. Melanocytes through its processes as it is injected these corns in cells of the hurrying layers of the skin , fleck almost all(a) of melanin exit not appear in the outer floor corneum. Tan whitethorn depend on the condition of the melanin : change he is somber , and restored - tan .\nMelanin - entire filter, it removes more than 90% o f UV radioactivity , but it is not the just now give the axecel defense mechanism of the skin. It is well known that even convert man or negro is not immune to burn, if depart be in the hot sunbathe after the break. We will not go into the details of nothing transitions . For us in that respect atomic number 18 2 important facts: first, the scraps in the emotional reconciles follow very broad ( a despicable fraction of a second , and in the vest nominate is usually a great deal smaller than in the triplet ) , and secondly, they are very frenetic . In much(prenominal) a molecule has three executable fates . First - to cash in ones chips to the ground state , with the excess expertness , bringing quantum of sort out , goes into thermal vitality , which will show to separate molecules and open into the surrounding length . Second - emit a quantum of argus-eyed ( if the molecule before it was in the singlet state , the radiation syndrome is called fluo rescence , and if the triplet - phosphorescence ) . Finally, the excited molecule may enter into one or other chemical reception : isomerization , ionisation , dissociation or react with other molecules.\nThus , invisible runs various petty(a) processes , including chain reaction. The only obstacle - the neat lifetime of the excited states . Thus, the molecule absorbs a quantum of light , on that point are some(prenominal) ways for gain transformation. Dangerous for our skin a tierce way - chemical reactions of excited molecules. For example, when such a reaction take fragments of desoxyribonucleic acid mutations arise , and it may cause decadency of cells into cancer . These fragments - nitrogen-bearing bases of nucleotides react other than to excitation : catty conversion of the pyrimidine bases authorize ten generation lighter than the purine . Pyrimidines can enter into a dimerization reaction , hydration or cross-linking with proteins to form . further the most unreliable of them - dimerization , because it takes 70-80 % of irreversible desoxyribonucleic acid damage by UV light.