CULTURE: Candidates sought for new £50 note

a socalled ‘‘chemical castration’’.

The ‘‘treatment’’ was designed to reduce libido and had the effect of rendering Turing impotent and causing him to grow breasts.

If this were not humiliation enough, his conviction also meant that Turing’s security clearance was revoked. As a consequence, he was barred from continuing the consultancy work for Government Communication Headquarters that had grown from his wartime codebreaking successes.

On June 7, 1954, Turing died of cyanide poisoning. Next to his bed lay a halfeaten apple. The inquest into his death recorded a verdict of suicide.

In 2009, then prime minister Gordon Brown apologised on behalf of the British government for the appalling way Turing was treated and in 2013 Turing received a posthumous royal pardon. In 2017, the Alan Turing law came into force, retrospectively pardoning all men convicted of ‘‘gross indecency’’ for acts no longer considered offences.

In light of his war heroism, his scientific prowess, his technological foresight, his farreaching computational influence and his stoicism in the face of injustice, the question is not ‘‘Why should Alan Turing feature on the new £50 note?’’ but rather, ‘‘How can we ignore this British icon any longer?’’

Christian Yates is a senior lecturer in mathematical biology at the University of

Bath.

OROTHY Crowfoot Hodgkin may be the most famous British scientist of whom most people have never heard. She was the foremost leader and innovator in her field and is the only female British scientist to win a Nobel Prize (so far). The 1964 award recognised her work using Xray crystallography to find out the threedimensional shapes of penicillin (1945) and vitamin B12 (1955).

Accurate knowledge of the shape of penicillin was pivotal in understanding how it could overcome bacterial infections. As a result, Hodgkin’s work is still extremely important in the development of new antibiotics.

Hodgkin’s work also had an enormous impact on the treatment of diabetes. In 1969, after 35 years’ work, she solved the 3D shape of the insulin molecule. Insulin is a hormone used by the body to process

Dsugars in food, and understanding its structure has helped untangle the mechanism of its action, with critical implications for diabetes control.

Key to Hodgkin’s work was the technique of Xray crystallography, a way of working out how a complex molecule is arranged in three dimensions. The way this is done is by growing tiny crystals of a substance so its molecules are lined up in an orderly array. We then hit this array with an intense beam of Xrays and capture the resulting ‘‘diffraction pattern’’ of spots that indicate how the molecules interfere with the beam.

By capturing patterns from each side of the crystal and doing some complicated mathematics, we can get the average of the shapes of all the molecules, highlighting all the common features. This gives us a picture of the density of electrons in the molecule in 3D space, which we can use to show how the atoms of the molecule are arranged.

Hodgkin’s work in crystallography gave birth to a new field that applied the methods she developed to large biologically important molecules, including DNA and proteins. We now know the 3D shapes of more than 139,000 biological molecules, and all the information is stored in an openaccess database.

Hodgkin’s legacy is multifaceted. She was not only an exceptional scientist but also was, and still is, an inspirational role model to generations of researchers, both male and, very importantly, female. She was also very active as a pacifist and a Quaker. For 12 years she was president of Pugwash, an organisation dedicated to reducing the danger of armed conflict and seeking peaceful solutions to global security threats. She even inspired her former student Margaret Thatcher, who reportedly kept a portrait of her in 10 Downing Street, despite their differing politics.

Her life was a shining example to many, so it would be entirely appropriate for us to give her the public recognition she deserves, by putting her image on our new £50 notes.

Elspeth Garman is a professor of molecular biophysics at the University of Oxford. — theconversation.com