The protein molecule in question is called bacteriorhodospin. Purple in color, it exists in the microorganism halobacterium halobium which thrives in salt marshes where temperatures can reach 140F. The protein undergoes a molecular change when subjected to light making it ideal for representing data.
Each molecular change is part of a series of many different states known as the photocycle. There are three main states: the bR state, the O state and the Q state. The O state represents binary 0 and the Q state represents binary 1 while the bR or rest state is neutral. To survive the harsh conditions of a salt marsh, the protein must be incredibly stable, a critical factor if it is to be used for representing data.