 Nonetheless, the controversy was eventually closed in the mid-1970s in Mitchell’s favor, earning him the 1978 Nobel Prize for Chemistry. The cause(s) for this closure are subject to interpretation. Most biochemistry textbooks as well as Weber (2002, 2005) cite a famous experiment by Ephraim Racker and Walter Stoeckenius (1974) as crucial for establishing Mitchell’s mechanism. These biochemists worked with synthetic membrane vesicles into which they had inserted purified enzymes, one of which being the mitochondrial ATPase (the enzyme directly responsible for phosphorylation of ADP). The other enzyme was not derived from mitochondria at all, but from a photosynthetic bacterium. This enzyme had been shown to function as a light-driven proton pump. When this enzyme was inserted into artificial membrane vesicles together with the mitochondrial ATPase, the vesicles phosphorylated ADP upon illumination.