Peter Hegemann

A question about a tiny organism

How does a single-celled alga respond to light? Peter Hegemann's work on this question helped reveal molecular mechanisms that would later become valuable to neuroscientists.

Hegemann was born in Münster in 1954 and grew up in Aachen. He studied chemistry in Münster and Munich, carrying out doctoral research in Dieter Oesterhelt's group at the Max Planck Institute of Biochemistry and completing his doctorate in 1984. Postdoctoral work with Kenneth Foster at Syracuse University was followed by a research-group position at the Max Planck Institute. He became a professor at Regensburg in 1993 and moved to Humboldt University of Berlin in 2004.

Light opens a molecular gate

Hegemann and collaborators studied proteins from the green alga Chlamydomonas reinhardtii. Their work helped establish that some of these proteins act as channels controlled directly by light. A channel is a route across a cell membrane through which particular ions, or electrically charged particles, can pass.

In collaboration with Georg Nagel, Ernst Bamberg and other researchers, this work identified channelrhodopsins. Channelrhodopsin-2 was described in 2003. When placed in suitable other cells, the protein could make their electrical state respond to illumination. This suggested a remarkable possibility: a natural light sensor could become an experimental tool.

From algae to neuroscience

Nerve cells communicate through electrical and chemical changes. Light-sensitive channels offered researchers a way to influence selected cells with precise timing. Other scientists, including Karl Deisseroth and his collaborators, helped develop these molecular discoveries into practical methods for studying neural circuits.

This wider approach is called optogenetics. Hegemann's contribution was rooted in understanding the proteins themselves: how light changes their behaviour and how that affects the movement of ions. He helped provide the molecular foundation on which other researchers could build.

Why basic science matters

In 2026, Hegemann shared the Nobel Prize in Physiology or Medicine with Karl Deisseroth and Georg Nagel. The path from algal light responses to neuroscience illustrates why scientists investigate fundamental questions even when the eventual applications are not yet clear. A discovery in a microscopic organism can become useful far beyond the original field.