Laser Induced Visual Pigment Conversions in Fly Photoreceptors Measured in vivo

The photochemical cycle of fly visual pigment was studied in vivo with laser methods. Two pulsed dye lasers were used, one delivering the visual pigment converting flash and the other testing the pigment state after a variable interval. Transmission through the rhabdomeres was measured in the eye of blowfly Calliphora erythrocephala. It followed that rhodopsin R490 converts into metarhodopsin M580 via two intermediates, with time constants of 700 ns and 80 µs respectively. In the reverse pathway, i.e. the photoconversion of metarhodopsin into rhodopsin, an intermediate decaying with a time constant of 4 µs was found.