Television Spectroscopy of Biological Fluorescence

Fluorescence emission spectra were obtained from single unfixed ascites tumor cells stained at 3.3 × 10
^-7
M to 3.3 × 10
^-4
M concentrations of the vital fluorochrome, acridine orange. The new RCA Intensifier Image Orthicon television camera tube was used as the light detector and afforded approximately a one-hundredfold increase in sensitivity over a standard image orthicon in this application. The light from the microscope was dispersed by a Leitz ``High Power'' Monochromator (exit slit removed) and the spectrum focused on the faceplate of the Intensifier Image Orthicon. Spectral curves were obtained by applying appropriate corrections to recordings of line selected oscilloscope traces. These curves show two emission peaks which indicate the presence of two molecular species in close agreement with in vitro data. Advantages of the technique and some implications of the results are discussed.