To begin with X-ray diffraction could only used to determine the structure of simple molecules. Organic compounds with large, complicated structures presented too much of a problem for the physical method at this stage and were largely characterised by long winded chemical methods. Nevertheless some molecules were too complicated for their structure to be solved by this method. However by the 1940's X-ray diffraction as a method of structure determination had been developed to such a degree that it was possible to determine even the most tricky structures.
Although indispensable, X-ray methods do not lead directly to the structure from experimental data. Large mathematical calculations and considerable chemical knowledge, imagination and intuition on the part of the scientist are required before a structural problem is solved. it was in this capacity that Dr. Hodgkin really excelled and resulted in her being awarded the Nobel prize in chemistry in 1964.
Dr. Hodgkin's work was also invaluable in the determination of the structure of penicillin. From 1942 onwards great numbers of chemists in the USA and Britain were working on the problem of the antibiotics composition, and the research was completed four years later. This was also the first occasion that computers were used to aid the complicated mathematical calculations. The synthesis of chemically related compounds for use as antibiotics was then possible and Dr. Hodgkin helped in the determination of these structures as well.
In 1948 she began work on the structure of vitamin B12. Humans need a ready made supply of this vitamin in their diet as it cannot be made in sufficient amounts. A dietary lack or inability to absorb it properly results in the blood condition pernicious anaemia which can be fatal. It was important, therefore, to be able to synthesis this substance for use as a dietary supplement. To do this you need to know it's correct structure.
Both these achievements were landmarks in the development of the structural determination of biological molecules. They were described as "a magnificent start to a new era of crystallography" and "the crowning triumph of X-ray crystallographic analysis" because of the difficulty and enormity of the tasks and of the biochemical and medical importance of the results.