Rhodopsin particles in the photoreceptor membrane of an insect.

Electron-microscopic examination of freeze-fractured fly retinae has revealed the presence of particles, 80 to 100 A in diameter, on the photoreceptor membrane. Flies which were raised on a vitamin-A deficient diet show a substantial reduction in the density of such particles. The reduction in particle density is in agreement with the reduction in visual-pigment concentration as measured spectrophotometrically for these flies. These results suggest that the particles are identical with molecules of the visual pigment, rhodopsin.