ABSTRACT
In the early 1970s scientists were €rst able to calibrate the physical speed of the essential light-sensing protein rhodopsin swimming or immersed in DHA-enriched membrane disks of rod cells of the eye (Liebman and Entine, 1974; Poo and Cone, 1974). These now classic studies demonstrate that rhodopsin rotates and moves laterally across the surface of membrane disks at amazing speeds (Figures 5.1a, 5.1b, and 5.1c). For biochemical studies large numbers of rod cells each containing about 1000 rhodopsin disks can be isolated from bovine eyes obtained from meat processing plants. The motional properties of integral membrane protein, rhodopsin, were calibrated using micro-lasers to rotate in a molecular swirl timed at 0.00002 seconds per turn. This remains atop the motion scale for a full swing of a membrane-bound protein and links DHA phospholipids with extreme membrane motion. Lateral motion of rhodopsin across the surface of membrane disks is also extremely fast and plays an important role in triggering the visual cascade. In this chapter we show how the unique conformational dynamics of DHA working in specialized neuron membranes is harnessed to maximize the motion of membrane components important in sensory perception and mental processes. We de€ne extreme speed as a state of membrane motion in which membrane lipids, proteins, lipophilic electron carriers, and other membrane components rotate and move laterally across the bilayer at extraordinarily high speeds with DHA-enriched rhodopsin disks serving as a standard.
