Channelrhodopsins are light activateble cation channels. The opening occurs if the retinal of this protein absorbs light and due to this changes its conformation. This light activateble channels are especially interesting for neuroscience because this channels inserted in a neuronal membrane can produce spike fireing. The protein is inserted in the cell by a virus witch manipulates the genome of the cell so that it produces the channels, this methode is called optogenetics. One problem with optogenetics is, that the light has to penetrate the tissue to get to the neurons with the channel. Because the most channelrhodopsins are activated by blue light and blue light gets highly absorbed by the tissue, the skull needs to be open to induced light on the neurons. Red lights doesn’t get absorbed this much by the tissue therefore a red shifted channelrhodopsin would be a much better tool. One of this is ReaChR (Red-Light-Activated channelrhodopsin), which is a synthetic channelrhodopsin. It is a chimera of ChR1 and ChR2. In my bachelorthesis I simulate a retinal isomerisation and analyse the behavior of the protein. With this simulations I try to characterise the ground and pre-open state of ReaChR