Biophysical and Cytological Studies with Laser Microbeams

Microirradiation with a conventional UV source (2750A), ruby (6943), neodymium (5300 or 2650) lasers was used. The true absorption of laser light by Janus green-stained mitochondria was determined by comparison with models containing known amounts of the dye. In the same way it was possible to show that thermal denaturation is limited to the stained organelles, and to define radiation time limits. Flash photolysis with the Q-switched laser permitted the comparison of the results of exciting various chromophores of importance in cellular microirradiation. Differences between the effects produced by microirradiation with an ordinary UV source and with a laser source of the same wavelength have been noted. Upon irradiation of a small portion of the cell nucleus with an ordinary UV source cut-and-patch repair of the nucleic acid lesions was shown. (Author)