Dorothy Crowfoot Hodgkin. Portrait of Dorothy Crowfoot Hodgkin (1910-94), the British X-ray crystallographer who discovered the structures of penicillin, vitamin B12 and insulin. Hodgkin developed the X-ray diffraction method of determining molecular structure devised by the Braggs. She then applied it to the study of complex organic molecules and used computers to perform massive computations on the results. She discovered the structure of penicillin in 1945 and that of vitamin B12 in 1956. In 1972 she described the structure of insulin (which has 800 atoms), a project she had started in the 1930s. She was awarded the Nobel prize for chemistry in 1964.