Early in the Second World War the successful tests with penicillin extracts on infected mice by Howard Florey and his team in Oxford led to urgent attempts to determine its chemical structure. Hodgkin and her co-workers accomplished this in three years with x-ray techniques. Since the research had been carried out under conditions of wartime secrecy, it was not until 1949 that Hodgkin and her collaborators' work was finally published in The Chemistry of Penicillin (Bibliog. 46). Research on penicillin refinements continued after the war.

Professor Hodgkin explained the scientific importance of the penicillin analysis in a letter to the compilers of this catalogue (July 1991): 'The usual way of establishing the structure of an organic natural product was by synthesis following experiments in degradation which suggested different possible structures. This proved impossible in the case of penicillin because the structure is unstable in the presence of the reagents needed to make B lactams. Much later routes to produce stable B lactams were discovered and put to the synthesis of penicillin. Other physical methods and particularly spectroscopic methods were inconclusive which left x-ray methods as the best evidence of the x-ray evidence at first; now it is commonly used first to find organic structures.'

The documentation of the penicillin research is of particular interest because of the importance of the molecule to medical science and the demonstration of the power of x-ray techniques in the solution of its structure by Hodgkin and her co-workers. Furthermore the enormous technical developments after the Second World War - especially the use of the electronic computer to process data - meant that the variety of methods pioneered in the analysis of penicillin were not in fact used again.

The material, which is substantial, covers the period 1942-89, although the bulk dates from the last years of the Second World War and the period immediately afterwards. There is an extensive correspondence with colleagues, drafts for reports and publications, reports of work of colleagues in other laboratories sent to Hodgkin for information or circulated officially, notebooks, data, and illustrative material probably prepared for a penicillin display at the Science Museum, London as part of an exhibition to mark the postwar International Congress of Pure and Applied Chemistry.