Characterization of activation energy distribution for ultraviolet irradiation of T-rich oligonucleotide using high-performance liquid chromatography electrospray ionization mass spectrometry tandem mass spectrometry. 
Exposure to solar UV radiation gives rise to mutations that may lead to skin cancer of human being.  Series of experiments were carried out in order to reveal activation energy distribution of DNA mutation caused by UV radiation.  The T-rich oligonucleotides were exposed to UV radiation with increasing intensity for different durations.  Photoproducts of T-rich oligonucleotide were investigated using ion-pair reversed-phase high-performance liquid chromatography/tandem electrospray ionization mass spectrometry (IP-RP-HPLC/ESI-MS) at room temperature.  Two photoproducts of T-rich oligonucleotide were cis-syn cyclobutane pyrimidine dimmer (T[c,s]T) and the pyrimidine(6,4)pyrimidone product (T[6,4]T).  Activation energy distribution of DNA mutation was calculated using a commercial kinetics analysis programs by Robert L. Braun and Alan K. Burnham , Lawrance Livermore International Laboratory (version 2.4.1).  To use the software for deriving the kinetics parameters, the factor T (temperature) in the software was substituted with k1R, in which k1 is a factor, R is radiation intensity.  The activation energy derived ranges from 55 to 110 kJ mol(-1).  By the same software, those kinetics parameters were extrapolated to natural UV radiation process to predict DNA damage degree without the DNA repair process.