Ultrafast molecular gymnastics
We owe our ability to see to the molecule retinal. In the human retina, a light-activated alteration in the structure of retinal triggers the neuronal reaction that is the basis of the visual sense. Bacteria also make use of the reaction to transport protons or ions across the cell membrane, which allows light energy to be stored and later consumed as a biological fuel. In all these cases, the retinal molecule is bound to a specific protein that plays a central role in modulating its response to light, which occurs within 500 femtoseconds. This is one of the fastest reactions in biology (1 fs is equivalent to a millionth of a billionth of a second). Researchers at the Paul Scherrer Institute (PSI) have now taken snapshots of what happens in this minuscule interval. “No one has previously measured the light-activated response of a retinal-binding protein with such precision,” says Jörg Standfuss, Leader of the Time-Resolved Crystallography Group in the Division of Biology and Chemistry at the PSI.