13 February 2008

The harmfulness of ultraviolet depends on the structure of DNA at the time of irradiation

Experts have long known that certain regions of the genome are particularly susceptible to the destructive effects of ultraviolet radiation. Scientists at Ohio State University hypothesized that the structure or shape of the DNA of skin cells at the time of exposure to ultraviolet radiation determines the likelihood of damage.

The double DNA chain is constantly fluctuating, undergoing billions of minor but distinguishable structural changes every second caused by the action of water molecules and other compounds.

DNA damage is relatively rare, because most of the time the structural organization of the chain provides protection from the harmful effects of ultraviolet radiation, but a small part of the molecules is always at risk. The most typical type of damage caused by ultraviolet radiation is the formation of a cyclobutane-pyrimidine dimer. This process is fraught with the appearance of mutations leading to skin diseases, including the development of malignant neoplasms.

The authors used heavy-duty computers to study the multimillion-dollar variety of forms taken by DNA in water and various biological solvents. The results of data processing obtained using molecular dynamics modeling indicate that cyclobutane-pyrimidine dimers are formed only at a certain location of adjacent thymidine DNA bases, which pass into an excited state under the action of ultraviolet radiation energy.

According to the authors, the results obtained are of great importance, because they reveal variants of conformations of the DNA molecule that increase its susceptibility to the harmful effects of ultraviolet light. They believe that this will help in studying the mechanisms that eliminate mutations that occur in living organisms under ultraviolet irradiation.

Article by Yu Kay Law et al. The Prediction of Thymine Dimerization Yields from Molecular Dynamics Simulations is published in the January issue of the Biophysical Journal.

Portal "Eternal youth" www.vechnayamolodost.ru based on the materials of ScienceDaily


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