Louise Johnson, director of life sciences, Diamond Light Source, Chilton, UK

When Louise Johnson was a student at University College London, physics was confined to either the very large or the very small. She was hesitant to choose either, as they seemed to require huge teams to advance the field. “I didn't see how I could make a contribution,” she says.

But then she recalled some X-ray crystallography work she had done as a student at the Royal Institution in London. She was aware that the technique was catching on – the 1962 chemistry Nobel was awarded to Max Perutz and John Kendrew for their determination of the structure of the proteins myoglobin and haemoglobin using X-rays (see CV).

Three years later Johnson was part of a team that used the same technique to solve the structure of the enzyme lysozyme. Although Johnson wasn't on the main structure paper, she was co-author of a companion piece that showed how the enzyme's structure helped it to carry out its task of attacking bacterial invaders. “That's really what opened people's eyes to this method – that we could understand biology by understanding structure,” she says.

From that moment on, Johnson knew that her career would be in structural biology. And that meant she needed to keep up with the latest technology to solve the structures of bigger and more complicated proteins and complexes. Her first use of a synchrotron light source, LURE, near Paris, provided “a breath-taking moment” when she realized that its greater power could cut down a molecule's exposure to X-rays by two orders of magnitude. That development allowed her to help solve the structure of the enzyme glycogen phosphorylase.

Since then, she's pushed for stronger, more powerful facilities – and more facilities devoted to biology. In the early years, she jokes, researchers tackling biological problems were considered ‘parasites’ by scientists studying purely physical phenomena.

Now, the tables are turned. As life-sciences director of the Diamond synchrotron near Oxford, UK, Johnson's remit is to ensure that the new light source, when it comes online in 2007, devotes a significant amount of time to biology.