Dorothy Hodgkin, OM, FRS, scientist and Wolfson Research Professor, University of Oxford, 1960-77, died yesterday aged 84. She was born on May 12, 1910.

The world recognised Dorothy Hodgkin as one of the outstanding scientists of the 20th century. She will always be remembered for her discovery of the structure of penicillin, of the antipernicious anaemia factor Vitamin B12 and of the diabetic hormone, insulin.

However, she will also be remembered as a unique human being a woman with no enemies, a woman of infinite understanding, compassion, simplicity and an enduring serenity. She was never too busy to help both the deserving and the undeserving in distress, caring about individuals as well as the needs of universities and society whether at home or abroad. Besides being a scientist she was a wife, a mother and a grandmother, and her home welcomed scientists, politicians and the down-and-out with unfailing warmth. This was based on the depth of love and understanding that existed between her and her husband Thomas, a distinguished Africanist and Arabist.

She had a modest but engaging approach to formal occasions. When summoned to the Palace to receive the Order of Merit it is said that she arrived on foot, approached one of the guards and simply said ``I want to see the Queen.'' Dorothy Mary Crowfoot, as she was before she married, was educated at the Sir John Leman School, Beccles, and at Somerville College, Oxford, where she later became a tutor and fellow, building up in the college a tradition of scientific scholarship in the days when few women read science. At Somerville one of her undergraduate students was Margaret Thatcher.

In 1946 she became a university lecturer and demonstrator; in 1956, University Reader in X-ray Crystallography and in 1960 Royal Society Wolfson Research Professor.

Her own scientific work began with H.M.Powell in Oxford and concerned certain compounds of thallium. In 1932 she moved from Oxford to Cambridge and, working with J.D.Bernal, began to explore the structures of an enormous range of molecules, many of them of biological importance. Amid a great deal of distinguished work, some of the crystals she studied at this time were to be particularly significant and of lifelong interest. The most exciting of the discoveries at Cambridge was to be longest in coming to fruition. In 1934 the first X-ray photograph of a crystalline protein, pepsin, was taken in Bernal's laboratory. A year later Hodgkin photographed, for the first time, insulin crystals of the form used when the structure was finally solved in 1969. Following an examination of suitably prepared (wet) crystals, a year or two later, she used the mathematical technique introduced by Patterson in 1935 to obtain some objective information about the arrangement of atoms within the molecules. Such an awareness of the possibilities of new methods always characterised her work.

At the time, in the absence of computers, a detailed determination of the arrangement of the atoms of a molecule as large as insulin, with more than 1,000 atoms, was impossible. After obtaining the important result which indicated the regularity of this molecule, Dorothy Hodgkin returned to the structures of smaller biologically interesting molecules, which were also entirely unknown. The first structures to which she applied the new objective methods were derivatives of the sterols, which had been the subject of her PhD thesis with Bernal, and her investigations confirmed their previous conclusions. Work on penicillin began in 1942, an investigation fraught with difficulties caused both by the nature of the crystals and by the fact that the chemical structure of the molecule was not known. Throughout this investigation, the chemical and crystallographic evidence were compared, and much ingenuity was required to obtain the correct structure in a problem so close to the limits of possibility. The important results led the way to the structures of a large number of antibiotics over the years, particularly of the cephalosporins. In 1970 the structure of the large and interesting compound, thiostrepton, with antibiotic properties, was determined. This molecule required, in its time, as much genius for its solution as did penicillin in the 1940s. Such an ability to choose and solve important problems at the limit of the technique was a continuing feature of Dorothy Hodgkin's work.

This was particularly evident in the determination of the structure of vitamin B12, the anti-pernicious anaemia factor. The first X-ray photographs were taken before even the size of the molecule was known, and from these, the size was determined. The investigation, from 1948 to 1956, demanded not only a great deal of painstaking hard work from many people, but also enormous insight. The structure of the important central part of the molecule was obtained by combining information from four slightly different compounds, one of which was a degradation product of vitamin B12. Again, the investigation showed the complementary nature of crystallographic and chemical investigations. It is, perhaps, the insulin structure which Dorothy Hodgkin had most wanted to see in full detail. Her early pictures in 1935 were taken when even the first principles of protein structure were in dispute. Advances in technique and in computer technology made determination of structures of this complexity possible. The early 1960s saw structures of important protein molecules such as haemoglobin, larger than insulin. For several years after that, the very close packing of insulin molecules in the crystal, commented on in her first papers, made the structure still difficult to solve.

However, in 1969, the structure of ``two zinc'' insulin was solved in such detail that the positions of the individual chemical groups could be seen. The tightness of the packing of the molecules of insulin now became useful, allowing even greater detail to be discovered. This detail was required by Hodgkin who expected to be able to define the position of each atom in order to understand the structure. Recent work has been directed toward increasing such detail and toward understanding the action of this molecule in the body. Her many and far-flung former students and colleagues will remember with gratitude and amazement her uncanny ability to choose the right from the wrong features, despite apparent evidence to the contrary, and even more her generosity and her ability to let them follow their own paths under an ever-watchful eye.

After her retirement from her Wolfson chair in 1977 she became a fellow of Wolfson College. But she had already, in 1970, become Chancellor of Bristol University and continued as such until 1988. There she is remembered for the intense interest she took in student affairs, particularly in the lives of overseas students. A facility in Bristol which offers accommodation to overseas students, opened in 1986, is named Hodgkin House in honour of her and her husband.

Another concern of hers during her time at Bristol was the Hodgkin scholarship for which she encouraged Bristol students to raise the money themselves. It was officially a scholarship ``for students from southern Africa'', but no one was in any doubt that what was really intended by it was to raise money for students from South Africa, who were battling apartheid and would certainly have not been able to get government backing for studies overseas. It was an initiative typical of her radical nature.

Another offshoot of this was her becoming, with another Nobel laureate, the physicist Sir Cecil Powell, a founder-member of ``Pugwash''. This was an international organisation of scientists whose aim was to keep lines of communication open between those working on this and the Warsaw Pact side of the Iron Curtain in the days of the Cold War.

A woman of indomitable spirit, she refused to let even severe arthritis call a halt to her scientific activity. Only last year, although wheelchair-bound, she flew to an international crystallography conference in Peking, to the astonishment of the other delegates who attended it.

Dorothy Hodgkin was awarded the Gold Medal of the Royal Society in 1956, the Nobel Prize for Chemistry for 1964 and was made a member of the Order of Merit in 1965. At the time of her death she was the senior member of the order. She was also a member of many of the great national scientific academies and the recipient of many honorary degrees from universities here and abroad. Her husband Thomas died in 1982, and she is survived by two sons and one daughter.