SUMMARY
Time of flight laser photoionization has been used to study the response of some molecules of biological interest under laser radiation. One of the questions of great interest today is the effect of radiation on DNA and RNA molecules. Damage to these molecules can be caused directly by radiation or indirectly by secondary electrons created by radiation. As response of the radiation field fragmentation process can occur producing different ions with kinetic energies of a few electron volts. In this paper we present the results of the interaction of 355nm laser with the nitrogen bases adenine(A) and uracil(U) using time-of-flight spectrometry and the comparison of experimental results on the effects of laser radiation in (A) and (U) belonging to two different ring groups, purines and pyrimidines respectively,which are linked to form the AU pair of the RNA.