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Photographing potassium, rubidium and sodium salts


Crystallising penicillin
Dorothy Hodgkin Scientist
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The next immediate thing was the actual crystallisation of penicillin itself, which made it unnecessary to try and work out the detailed structure of the separate...

[Q] Exercise?

And the, this was, the sodium salts were crystallised in the Squibb Institute, and I rang up Edward Abraham and said, make me some sodium salt quickly, and he said, oh, you don't need to make it, we've got buckets of it. We keep it in a desiccator. So we took the sodium salt, their sodium salt, out of the desiccator, and put a lump of it on a slide which I was taking up to the look at under the microscope. And it immediately took up water from the air and crystallised on the slide with the water of crystallisation. Well, that was, in fact, two-pentenyl penicillin, and it had a slightly complicated molecular molecule. The weight suggested there were two molecules in each cell and a certain amount of water. And I think, from observations since, made by our people in other labs, that, in fact, if it had been crystallised from acetone, it might have been as simple as benzylpenicillin. But at least we knew that the benzylpenicillin was a new molecule, equals two molecules that we could use, and obviously much better for us. So I asked Henry Dale whether he'd get... I think he offered to get some for me from, from America and he did in fact get about 10 mg from Merck, and this... Kathleen Lonsdale brought over from London by hand, and I remember, sort of immediately, it came in a little tube. I took some out of it to crystallise, to try to recrystallise, because the crystals were quite small. And I had a telegramme from them in America saying, ‘Dissolve in minimum - emphasise the minimum...’ and I think, I forget what it was actually in, but it's in the book, and then add dropwise until crystals start to grow. So I carried out this process of dissolving it in two drops of ethyl acetate and having the precipitant. And Kathleen and I were just walking at the bottom of the little... talking at the bottom of the little ladder in the X-ray room, while I had this up top on the shelf above, so we left this there while we were talking, and then we saw that the crystals grew quite nicely in layers. And after a time they didn't grow any more, so I then took out the largest that I could see, and put it on the X-ray tube, and we took the first photographs. And they looked to us perfectly good enough to work on. So, in fact, I worked on those crystals, and particularly on the one I had first picked out. I just took the whole set of Wiessenberg photographs of it for the three-dimensional data, and that... the whole of the structure practically came out of that one crystal.

British pioneer of X-ray crystallography, Dorothy Hodgkin (1910-1994), is best known for her ground-breaking discovery of the structures of penicillin, insulin and vitamin B12. At age 18, she started studying chemistry at Somerville College, Oxford, then one of the University of Oxford colleges for women only. She also studied at the University of Cambridge under John Desmond Bernal, where she became aware of the potential of X-ray crystallography to determine the structure of proteins. Together with Sydney Brenner, Jack Dunitz, Leslie Orgel, and Beryl Oughton, she was one of the first people in April 1953 to see the model of the structure of DNA, constructed by Francis Crick and James Watson. She was awarded the 1964 Nobel Prize in Chemistry and is also known for her peace work with organisations such as Science for Peace and the Medical Aid Committee for Vietnam. All recorded material copyright of The Biochemical Society.

Listeners: Guy Dodson

Guy Dodson studied chemistry and physical science at the University of New Zealand, followed by a PhD on the crystallographic study of an alkaloid. In 1961, he came to Oxford to work on the crystal structure of insulin. In the mid 1970s Guy and his wife moved to York University to establish a laboratory. In addition to insulin studies the laboratory has investigated many complex molecules of medical significance, including haemoglobin, myoglobin, HIV related proteins, proteases and proteins involved in managing nucleic acids in cells. In 1993, he went to the NIMR in London to establish a crystallographic group in an environment that spanned molecular, physiological and disease-related disciplines. Here his research began on some cell signalling proteins. His interests on medically relevant proteins included prions, malarial and TB proteins, and some clinically relevant thrombin inhibitors. Guy Dodson retired in 2004 but is still finding much to do in York and the NIMR.

Tags: crystallisation, penicillin, sodium salt, molecule, benzylpenicillin, crystals

Duration: 4 minutes, 25 seconds

Date story recorded: 1990

Date story went live: 02 October 2009