earticle

영어

The two major forms of the pyrimidine dimers are known to be the cyclobutane pyrimidine dimers (CPDs) and pyrimidine-pyrimidone (6-4) photoproduct. CPD the 6‐4 photoproduct of thyminehave been reported to cause structural changes of DNA, such as bending or kicking by 30℃ and 40℃, respectively. The conventional methods using circular dichroism spectroscopy and atomic force microscopy for monitoring the structural deformation of DNA are time consuming and instrument oriented. In recent, we observed red to purple color change of AuNPs only after mixing with UV‐irradiated DNA in a high salted buffer. The color changes of the mixture was dependent on UV irradiated time and base compositions of the UV‐irradiated DNA. The stability of gold nanoparticles in a high ionic strength solution is maintained by straight ssDNA adsorbed physically on the AuNPs. Single‐stranded and striated DNAs are known to adsorb onto AuNP by uncoiling themselves to facilitate electrostatic interactions between the bases and AuNPs. The UV irradiation to DNA accumulated a conformational deformation of the DNA structure by multiple‐dimer formation. However, the covalent bonds formed in the pyrimidine dimers could impose more stiffness on the UV irradiated DNA. As a result, the UV‐irradiated DNA became more rigid and thus could not effectively uncoil the compacted structure for the electrostatic interaction with AuNP and resulted in AuNP aggregation under the high salt condition. This hypothesis was supported and confirmed with no observation of any mass of fragmented DNA or radical oxygen species under the UV irradiation. It has been also known that the pyrimidine dimers are formed as result of triplettriplet energy transfer by exogenous drugs. Because our method does not require any chemical or biochemical treatments or special instruments for purifying and qualifying the DNA photolesions, it should provide a feasible tool for the studies of the UV‐induced mutagenic or carcinogenic DNA dimers and accelerate screening of a large number of drug candidates.