on a rat liver membrane receptor—the cellular discriminator that receives outside signals. Rodbell discovered that ATP (adenosine triphosphate) could reverse the binding action of glucagon to the cell receptor and thus dissociate the glucagon from the cell altogether. He then noted that traces of GTP (guanosine triphosphate) could reverse the binding process almost one thousand times faster than ATP. Rodbell deduced that GTP was probably the active biological factor in dissociating glucagon from the cell's receptor, and that GTP had been present as an impurity in his earlier experiments with ATP. This GTP, he found, stimulated the activity in the guanine nucleotide protein (later called the G-protein), which, in turn, produced profound metabolic effects in the cell. This activation of the G-protein, Rodbell postulated, was the "second messenger" process that Earl W. Sutherland had theorized. In the language of signal transduction, the G-protein, activated by GTP, was the principal component of the transducer, which was the crucial link between the discriminator and the amplifier. Later, Rodbell postulated, and then provided evidence for, additional G-proteins at the cell receptor that could inhibit and activate transduction, often at the same time. In other words, cellular receptors were sophisticated enough to have several different processes going on simultaneously. Rodbell's personal philosophy of science He concluded his formal written Nobel Lecture with this poem:To my Friends:Thoughts from “On High” Life on a roller coaster, oscillating from hither to yon, no respite for the iconoclast, wandering from dusk to dawn. Conjuring strange thoughts foreign and twice forbidden, like Prometheus unbound, this Nobelist climbs in vain to Andean peaks, seeking what most would proclaim insane. Why, he ponders, are there no answers to protean questions when others thinking cleanly and simply with Occam’s sharp razor proclaim what seems obvious given the beam of their unerring laser. Nature, happily unfettered with philosophy, or with cunning, or with intent moves relentlessly onward or even backward with energy unspent while we mortals test and probe with twinkling machines blinking precisely at each movement, striving to unravel its irresolute randomness, its fathomless, unlimited, meaningless rush into spiraling chaos, oblivious of its multitudinous trials & errors which we pontifically believe must be unerring truth & resolution. The laugh is on those who, burdened with pretensions of truth, believe they can fathom within 15 minutes of human existence what has transpired over eons of space and time in this Universe . So,