PHOTOACTIVE TERTHIOPHENES: THE INFLUENCE OF SERUM ON ANTI‐HIV (HUMAN IMMUNODEFICIENCY VIRUS) ACTIVITIES

Responses of Chlamydomonas to light, such as phototaxis and photophobic response, are thought to depend on a phototransduction process involving rhodopsin and a calcium ion influx at the eyespot. To assess the direction of the chromophore orientation within the eyespot, I measured the membrane current in cells captured by a suction pipette upon stimulation with polarized light. When the cells were stimulated with polarized light incident parallel to the membrane overlying the eyespot, the photoreceptor current was found to change with the direction of the e‐vector. The current was maximum when the e‐vector was parallel to the eyespot membrane and minimal when perpendicular. When the cells were stimulated with light incident perpendicular to the eyespot membrane, the photoreceptor current did not change with the direction of the e‐vector. These results suggest that the chromophore is located in the eyespot and oriented almost parallel to the plane of the membrane of the eyespot. Thus the direction of the chromophore orientation in Chlamydomonas rhodopsin with respect to the membrane is the same as in rhodopsins from bacteria and animals.