The interplay of supercoiling and thymine dimers in DNA

Thymine dimers are a major mutagenic photoproduct induced by UV radiation. While they have been the subject of extensive theoretical and experimental investigations, questions of how DNA supercoiling affects local defect properties, or, conversely, how the presence of such defects changes global supercoiled structure, are largely unexplored. Here we introduce a model of thymine dimers in the oxDNA forcefield, and validate it by comparison to melting experiments and structural measurements of the thymine dimer induced bend angle. We performed extensive molecular dynamics simulations of double-stranded DNA as a function of external twist and force. Compared to undamaged DNA, the presence of a thymine dimer lowers the supercoiling densities at which plectonemes and bubbles occur. For biologically relevant supercoiling densities and forces, thymine dimers can preferentially segregate to the tips of the plectonemes, where they enhance the probability of a localized tip-bubble. This mechanism increases the probability of highly bent and denatured states at the thymine dimer site, which may facilitate repair enzyme binding. Thymine dimer-induced tip-bubbles also pin plectonemes, which may help repair enzymes to locate damage. We hypothesize that the interplay of supercoiling and local defects plays an important role for a wider set of DNA damage repair systems.

Molecular Dynamic and Docking Simulation to Prevent Thymine Dimer as the Main Reason for Skin Cancer

Two major types can be repaired UV-induced DNA lesions. The first one is a light-dependent process that reverts UV damage applying particular wavelengths. The second is a light-independent process that excises the light-damaged region under novo synthesis of an intact DNA. The iGEMDOCK has been used for this study, and the acceptable thymine dimer can be defined for the binding site in whole DNA structures. The DNA is worked with two thymine in a segment of nucleic acids, and iGEMDOCK can help to prepare a suitable binding between them. The total energies of the model systems are a total of several partial energies as follows: E(system) = E(bond) + E(angle) + E(torsion) +E(over) +E(vdW) + E(Coulomb) + E(Specific). EvdW +E(Coulomb) represents the dispersive and electrostatic energies contribution between all atoms, respectively. Finally, E(Specific) is system-specific energy such as lone-pair, conjugation, and hydrogen binding. The DFT and HF calculations of the thymine dimer exhibited that the ring fusion at the C5 and C6 atoms of two thymine bases produced a four-member cyclo-butane puckered ring, as well as the feature, is seen with the MPn or Moller-Pleset level. In addition, the UV radiations between 360 nm to 200 nm have been investigated for the study of thymine dimers.

Thymine dissociation and dimer formation: A Raman and synchronous fluorescence spectroscopic study

In this study, absorption, fluorescence, synchronous fluorescence, and Raman spectra of nonirradiated and ultraviolet (UV)-irradiated thymine solutions were recorded in order to detect thymine dimer formation. The thymine dimer formation, as a function of irradiation dose, was determined by Raman spectroscopy. In addition, the formation of a mutagenic (6-4) photoproduct was identified by its synchronous fluorescence spectrum. Our spectroscopic data suggest that the rate of conversion of thymine to thymine dimer decreases after 20 min of UV irradiation, owing to the formation of an equilibrium between the thymine dimers and monomers. However, the formation of the (6-4) photoproduct continued to increase with UV irradiation. In addition, the Raman spectra of nonirradiated and irradiated calf thymus DNA were recorded, and the formation of thymine dimers was detected. The spectroscopic data presented make it possible to determine the mechanism of thymine dimer formation, which is known to be responsible for the inhibition of DNA replication that causes bacteria inactivation.

Removing skin-cancer damaging based on destroying thymine dimer complexes

Cyclobutane pyrimidine dimers including thymine or uracil have been studied and characterized through several spectroscopic methods. The azetidin intermediates are generated when the 3’-end bases are cytosine group, through cycloaddition of the 4-imino functional of the latter pyrimidin base. Spontaneous rearrangement of the oxetan or azetidin yields rises to the pyrimidin (6-4) pyrimidon adducts. Chemical shifts, isotropies, anisotropies, spans, asymmetries, and other properties are all the integrals of those current densities that can be explained through magnetic criteria and are the trustworthy accounts of the currents induced via external magnetic field capabilities