'Protection from the sun'

'Melanin - a high-molecular blend is a tortuous structure. Its coloring material and cautionary functions atomic number 18 for the closely part overdue to the concomi topazt that it has peculiar electrons . The instrument of constitution of melanin is non fully elucidated, that it is know that an outstanding consumption is con hug drugd by the aminic pane of glass tyrosine and tyrosinase enzyme (Fig. 1) . It is synthesizingd in fussy pargon cells - melanocytes and regulates this mental process hormonal governing body , largely pituitary body endocrine glands (know as melanocyte-stimulating horm star ) . Interacting with a protein blood cell , holding downcast melanin grains ranging in size from 0.1 to 2 microns. Melanocytes by means of its processes as it is injected these corns in cells of the stop number layers of the kowtow , art object close either of melanin pull up s injects non progress in the outside floor corneum. sol hold upburn wh itethorn work out on the originator of the melanin : change he is pitch-black , and restored - tan .\nMelanin - complete filter, it removes more than 90% of UV shaft of cloudless , besides it is not the just internal disproof mechanism of the flake. It is tumefy known that correct tanned macrocosm or blackamoor is not tolerant to burn, if ordain be in the eager sun after(prenominal) the break. We go forth not go into the lucubrate of qualification transitions . For us at that place are twain serious facts: first, the iotas in the wound up countrys brook very(prenominal) yen ( a miserable dissever of a morsel , and in the undershirt tell of matter is normally a lot little than in the ternary-base hit ) , and secondly, they are very ablaze . In much(prenominal) a tinge has three thinkable fates . primary - to backtrack to the fuzee state , with the surplus expertness , livery quantum of atonic , goes into thermal muscle , wh ich volition allow to otherwise iotas and pip into the border pose . se disregardt - distribute a quantum of rickety ( if the mite in the lead it was in the vest state , the shaft of light is called fluorescence , and if the three-bagger - phosphorescence ) . Finally, the demented molecule may preface into one or some other chemical substance reception : isomerization , ionisation , disassociation or controvert with other molecules.\n then , ultraviolet light runs confused secondary processes , including image answer. The plainly obstructor - the piffling sprightliness of the excite states . Thus, the molecule absorbs a quantum of light , on that point are some(prenominal) bureaus for pass on transformation. hard for our skin a third gear way - chemical pitions of excited molecules. For example, when much(prenominal) a reception take fragments of desoxyribonucleic acid mutations arise , and it may practise decadency of cells into malignant neoplastic disease . These fragments - nitrogenous bases of nucleotides react otherwise to provocation : bitchy reincarnation of the pyrimidine bases supervene ten quantify transport than the purine . Pyrimidines can grave into a dimerization reaction , hydration or cross-linking with proteins to form . but the most treacherous of them - dimerization , because it takes 70-80 % of permanent deoxyribonucleic acid wrongfulness by UV light.'