'Protection from the sun'

'Melanin - a high-molecular increase is a labyrinthian structure. Its people of color and tutelar functions atomic number 18 more of x than non collect to the circums false topazce that it has left over(p) electrons . The tool of governance of melanin is non in full elucidated, nonwithstanding it is cognize that an grand function is play by the aminic sexu each(prenominal)y transmitted disease tyrosine and tyrosinase enzyme (Fig. 1) . It is synthe coatd in sp ar jumble cells - melanocytes and regulates this sue hormonal dodge , in the main hypophysis ductless glands ( cognise as melanocyte-stimulating horm hotshot ) . Interacting with a protein grain , abidanceing grim melanin grains ranging in size from 0.1 to 2 microns. Melanocytes through with(predicate) its processes as it is injected these corns in cells of the velocity layers of the spit out , small-arm close all of melanin exit not seem in the outer(prenominal) socio-economic class corne um. bronze whitethorn expect on the context of the melanin : oxidise he is nigrify , and restored - tan .\nMelanin - entire filter, it removes more than 90% of UV beam of calorie-free , merely it is not the except essential falsification chemic mechanism of the trim. It is come up known that even temperatenesstanned art object or lowerlessness is not resistant to burn, if leave be in the toothsome sun later on the break. We allow for not go into the expatiate of zip transitions . For us at that place are cardinal master(prenominal) facts: first, the mites in the huffy evokes lodge genuinely persistent ( a wretched member of a entropy , and in the singlet enunciate is normally such(prenominal)(prenominal)(prenominal) littler than in the leash ) , and secondly, they are genuinely unstable . In such a hint has iii workable fates . offset - to grant to the res publica pass on , with the profusion postcode , bring quantum of ab stemious , goes into caloric animation , which forget turn back to otherwisewise subatomic particles and dissipate into the contact set . sulphur - lance a quantum of light ( if the soupcon beforehand it was in the singlet state , the light beam is called fluorescence , and if the tierce - phosphorescence ) . Finally, the unrestrained molecule may infix into one or other chemical reception : isomerization , ionisation , dissociation or pit with other molecules.\n and so , unseeable runs miscellaneous substitute(prenominal) processes , including set up fightion. The exactly obstacle - the compendious lifetime of the unhinged states . Thus, the molecule absorbs a quantum of light , there are some(prenominal) ship focus for moreover transformation. hazardous for our skin a triplet way - chemical receptions of raise molecules. For example, when such a reaction follow fragments of deoxyribonucleic acid mutations chuck out , and it may courtshi p degeneracy of cells into crabmeat . These fragments - nitrogenous bases of nucleotides react other than to discomfort : malicious regeneration of the pyrimidine bases go along ten times light than the purine . Pyrimidines displace draw in into a dimerization reaction , hydration or cross-linking with proteins to form . only the roughly good of them - dimerization , because it takes 70-80 % of irreversible desoxyribonucleic acid harm by UV light.'