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Abstract:
The sensitizing pigment hypothesis for the high UV sensitivity in fly photoreceptors (R1–6) is further substantiated by measurements of the polarisation sensitivity in the UV. The quantum yield of the energy transfer from sensitizing pigment to rhodopsin was estimated by electrophysiological measurements of the UV sensitivity and the rhabdomeric absorptance (at 490 nm) in individual receptor cells. The transfer efficiency is ≥ 0.75 in receptors with an absorptance in the rhabdomeres of 0.55–0.95. This result suggests that the sensitizing pigment is bound in some way to the rhodopsin. A ratio of two molecules of sensitizing pigment per one rhodopsin is proposed.
