The Development of Receptor Theory G.G.Stokes,a physicist at Cambridge,observed in 1864 spectral changes occurred when oxygen was removed from blood or subsequently reintroduced to blood.This finding demonstrated molecular interactions between two substances,implicating a complex between oxygen and hemoglobin. As will be discussed later,one hemoglobin molecule can bind 4 oxygen molecules,and there is a positive cooperativity of binding of molecular oxygen to hemoglobin. The Development of Receptor Theory Paul Erhlich(1854-1915)was a German bacteriologist who attempted to find a 'magic bullet'to cure syphilis and was a pioneer in the study of immunology.One of his findings was made when he incubated toxins with anti-toxins in a test tube.Erhlich found that antigen- antibody interactions are direct chemical encounters and not generalized phenomena as they require an ongoing biological process in the whole body.He also coined the term"chemotherapeutic index",meaning the ratio of the minimal curative dose to the maximal tolerated dose.The Development of Receptor Theory G.G. Stokes, a physicist at Cambridge, observed in 1864 spectral changes occurred when oxygen was removed from blood or subsequently reintroduced to blood. This finding demonstrated molecular interactions between two substances, implicating a complex between oxygen and hemoglobin. As will be discussed later, one hemoglobin molecule can bind 4 oxygen molecules, and there is a positive cooperativity of binding of molecular oxygen to hemoglobin. The Development of Receptor Theory Paul Erhlich (1854-1915) was a German bacteriologist who attempted to find a 'magic bullet' to cure syphilis and was a pioneer in the study of immunology. One of his findings was made when he incubated toxins with anti-toxins in a test tube. Erhlich found that antigen￾antibody interactions are direct chemical encounters and not generalized phenomena as they require an ongoing biological process in the whole body. He also coined the term “chemotherapeutic index”, meaning the ratio of the minimal curative dose to the maximal tolerated dose