June 19, 2009
Trying to controvert a seemingly incontrovertible law is a hard job. And Stefan Hell discovered just how hard when he attempted to thwart the resolution limit of optical microscopes. Initially, his ideas fell on deaf ears. Today, however, Stefan Hell is a Director at the Max Planck Institute for Biophysical Chemistry.
Text: Uta Deffke
One Saturday morning in the fall of 1993, Stefan Hell was sitting in his student apartment in Turku in southwest Finland, leafing through a book on quantum optics. The physicist from Heidelberg had just settled in the chilly north and he was hot on the trail of an idea that had been driving him for years: to revolutionize the resolving power of light microscopes.
For 120 years, the findings of German physicist Ernst Abbe in 1873 were considered to be set in stone: it is impossible to discern similar structures smaller than 200 nanometers in size with a light microscope. Stefan Hell is now pushing this limit. “I was convinced that it could be done,” he says. For years after completing his doctorate in physics, he struggled to obtain one stipend after the next, as few – if any – seriously believed in his idea. The concept alone was too absurd.
Although he had a rough plan for overcoming the resolution limit, he lacked the decisive trick to make it a reality. As he scanned through the book in search of suitable quantum optic phenomena, his eye was caught by the “stimulated emission” by which molecules that are excited to fluoresce can be switched off temporarily. “At that moment, it dawned on me. I had finally found a concrete concept to pursue – a real thread.” Biologists today study numerous cell processes with the aid of fluorescence microscopy, in which proteins and other cell components are marked with luminescent molecules.