= Georg Nagel
{c}
<Georg Nagel> studies membrane <proteins> that respond to <light>. His work on <channelrhodopsin-2> helped establish the molecular basis of <optogenetics>, in which introduced light-sensitive <proteins> allow <light> to control cellular electrical activity.
In 2003, Nagel and colleagues expressed <channelrhodopsin-2> from the <microalga> <Chlamydomonas reinhardtii> in <Xenopus laevis> <oocytes> and mammalian <cells>. Electrical recordings showed a rapidly opening <ion channel> permeable to <cations>. Experiments on isolated membrane patches supported direct gating by <light>, without requiring a freely diffusible intracellular intermediary. During sustained illumination the initial <electric current> declined to a lower maintained level.<Channelrhodopsin-2, a directly light-gated cation-selective membrane channel by Georg Nagel and others>[PNAS 100, pp. 13940–13945; abstract and membrane-patch recordings]{ref}
This gives a useful distinction between an <ion channel> and a molecular pump: an open <channelrhodopsin-2> permits <ions> to move down their <electrochemical gradient>. The resulting change in <membrane potential> depends on the <cell> and its ionic conditions; a flash of <light> does not imply an identical electrical response in every <cell>.<Channelrhodopsin-2, a directly light-gated cation-selective membrane channel by Georg Nagel and others>[Abstract; passive ion conductance and heterologous expression]{ref}
\Image[https://idw-online.de/de/newsimage428165?size=screen]
{title=Georg Nagel}
{description=Photograph by Rudi Merkl, Universität Würzburg. Identity and credit: https://idw-online.de/de/image?id=428165&size=screen.}
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