Mobility and electric charge of screening pigment granules in the superposition eye of Ephestia kuehniella Z.

The mobility and the electric charge of screening pigment granules of the mealmoth superposition eye were determined electrophoretically in buffer solutions. In potassium phosphate buffer the mobility of the negatively charged granules is linearly dependent on the pH in the range from 4.8 to 7.7, and in veronal buffer from pH = 2.3 to pH = 7.5. At pH = 6.6 the values of the effective charge per granule vary between 9.4 X 10(-17) C and 2.0 X 10(-16) C, those of the real charge between 2.4 X 10(-14) C and 5.6 X 10(-14) C. For equal electric fields, the mobility of the granules decreases with increasing ionic strength mu, and it remains the same for mu greater than 0.075 mol/l.