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About Her Life
Dorothy Crowfoot Hodgkin (1910–1994) was born in Cairo, Egypt, to English parents, John and Grace Crowfoot. Although her formal schooling took place in England, she spent a significant part of her youth in the Middle East and North Africa, where her father was a school inspector. Both her parents were authorities in archaeology, and she almost followed the family vocation; but from childhood she was fascinated by minerals and crystals. She enjoyed using a portable mineral analysis kit given to her when she became interested in analyzing pebbles that she and her sister found in the stream running through the Crowfoots’ garden in Khartoum, Sudan. When she was 15, her mother gave her Sir William Henry Bragg's Concerning the Nature of Things (1925), which contained intriguing discussions of how scientists could use X-rays to “see” atoms and molecules.
At Somerville College, Oxford, she studied physics and chemistry and chose to do her fourth-year research project on X-ray crystallography—using X-rays beamed into crystals to determine where the various atoms are located in three dimensions in molecules. In other words, scientists can determine the 3-D molecular structure of a substance by turning the substance into a crystal (if it is not one already), shooting some X-rays at the crystal, and then studying the way the X-rays are diffracted off the planes of the crystal’s structure. The technique, which involves a lot of mathematical analysis, was developed by William Henry Bragg and his son, William Lawrence Bragg, who won the Nobel Prize in 1915 “for their services in the analysis of crystal structure by means of X-rays.” Yet X-ray crystallography was still a relatively new technology with many challenges, and hence opportunities for research, when Hodgkin started working in the field.
After graduation she seized the opportunity to study at Cambridge with John Desmond Bernal, who had worked for five years with the senior Bragg. She and Bernal collaborated successfully, using X-ray crystallography to determine the 3-D structure of several complex organic molecules important to the functioning of living organisms. (The Braggs had worked primarily with inorganic molecules while developing their methods.) In 1937 she received her Ph.D. from Cambridge—the same year she married Thomas L. Hodgkin, who became an authority on African history. Both Hodgkins held academic appointments at Oxford, and they raised their three children there with the help of the Hodgkin grandparents.
Dorothy Hodgkin’s most significant discoveries were the determination of the structures of vitamin B12, insulin, and penicillin. In 1964 she won the Nobel Prize in Chemistry “for her determinations by X-ray techniques of the structures of important biochemical substances.” She was the third woman ever to win the prize in chemistry (after Marie Curie and Irène Joliot-Curie).
The case of penicillin took several years for Hodgkin to crack. Penicillin, which is actually a secretion from a mold called Penicillium notatum, was first discovered as a potential “bacteria killer” in 1928 by Alexander Fleming. By 1940 some of Hodgkin’s fellow scientists at Oxford University, principally Howard Florey and Ernst Chain, had shown that penicillin could fight bacterial infections in laboratory mice. Aware of the great potential for the drug in humans, they also foresaw a problem. Penicillin was difficult to extract from all the other substances in the mold cultures—tiny amounts were laboriously separated out. Florey and Chain knew that as more penicillin was needed to treat people, there would have to be a better way to produce more of it. One solution was to pursue large-scale industrial means of extracting the penicillin from the mold cultures. Another was to synthesize the drug artificially in the lab. The latter is where Hodgkin came in. In order to synthesize a substance in the lab, its molecular structure has to be known. On the very day that Chain received the results of animal testing, he encountered Hodgkin on campus and promised her, “Some day we will have some crystals for you to work on.”
But Hodgkin and her colleagues faced a few hurdles. Getting an organic substance such as penicillin to crystallize was (and still is) one problem. Why does the penicillin—or any substance, for that matter—have to be crystallized in order to examine it using X-rays? Imagine trying to nail down the structure of a substance when its atoms are constantly in motion. A crystal is a solid form of an element, compound, or mixture and has a regularly repeating internal arrangement of its atoms. X-ray crystallization works, in part, because atoms are held fixed in rigid and patterned arrangements in crystals. So crystals are ideal structures for X-rays to bounce off of, creating regular patterns that can then be deciphered using the Braggs’ complex formulas. But it’s not very easy to get every substance to form crystals, and that was Hodgkin’s first challenge.
Another difficulty was X-ray crystallography’s need for a lot of backup mathematical calculations. Today’s computers can crunch numbers at lightning speed, but during World War II computers were in their infancy. So finding a molecular structure via X-ray crystallography in Hodgkin’s time took many months, even years.
Meanwhile, a British-American effort by government and industry was organized to produce penicillin to treat soldiers sickened from the many infections and infectious diseases prevalent in the unsanitary conditions of battlefields. The planners encouraged both scientists who, like Hodgkin, were working on the synthetic route to penicillin, as well as those who, like Margaret Rousseau, were engaged in developing processes and equipment to make tremendous quantities of penicillin from the natural mold.
It took until 1945 for Hodgkin and her group to determine penicillin’s structure. Actually, they were confirming one of the two competing structures proposed by chemists working with pre–X-ray crystallization methods. Hodgkin’s information proved most useful after the war when semisynthetic antibiotics based on penicillin, such as ampicillin, were developed.
Hodgkin is fondly remembered by her group of research students, which included many women. She was also involved in a wide range of peace and humanitarian causes and was especially concerned for the welfare of scientists and people living in nations defined as adversaries by the United States and the United Kingdom in the 1960s and 1970s—for example, the Soviet Union, China, and North Vietnam. From 1976 to 1988 she was chair of the Pugwash movement, which was originally inspired by the concerns voiced in 1955 by Albert Einstein and the philosopher-mathematician Bertrand Russell that work by scientists—such as the creation of the hydrogen bomb—would lead to conflict and needed the insights of and input from the world's scientists. Later the Pugwash conferences dealt with other potential dangers raised by scientific research.
Hodgkin was honored many times throughout her life. In addition to being a Nobel laureate, she received the United Kingdom’s Order of Merit. She died at her home in England in 1994.
Adapted from Mary Ellen Bowden, Chemical Achievers (Philadelphia: Chemical Heritage Foundation, 1997).
For Further Reading on the Web
The Nobel Prize in Chemistry 1964 — from NobelPrize.org.
Remembering Dorothy Hodgkin — a personal reminiscence on the British Crystallographic Association’s Web site, reprinted from the American Crystallographic Association’s Fall 1995 newsletter.
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