June 08, 2011
In addition to bacteria and eukarya, archaea form the third domain in the three-domain system of life. Some of these organisms, like plants, need only the sun as a source of energy. As the third domain of life, they have also developed a variant of the photosynthesis that occurs in plants: instead of light-sensitive chlorophyll, they use the energy in sunlight, together with vitamin A aldehyde or retinal, for their metabolic processes. The retinal protein bacteriorhodopsin acts as a molecular pump, channelling positively charged hydrogen atoms through the cell membrane and thus transforming light energy into chemical energy.
Dieter Oesterhelt is the discoverer of bacteriorhodopsin. The chemist, who was born in Munich in 1940, has conducted research at a number of institutions including the University of California in San Francisco, the Max Planck Society’s Friedrich Miescher Laboratory in Tübingen (Germany) and the University of Würzburg (Germany). He has been Director at the Max Planck Institute of Biochemistry in Martinsried since 1979. “Dieter Oesterhelt’s work has opened up the completely new research field of biological energy. The Stifterverband’s prize recognises not only the excellence of his research, but also his perseverance in the face of initial doubts about his new ideas,” emphasizes Peter Gruss, President of the Max Planck Society.
The scientist is largely to thank for the fact that bacteriorhodopsin is currently one of the most widely studied membrane proteins. Dieter Oesterhelt and his colleagues were the first to breed bacteriorhodopsin crystals. This enabled them to decode the composition and three-dimensional structure of the protein. The methods developed for this process now form the basis for the structural analysis of membrane proteins. The Martinsried-based researchers also described an additional light-driven ion pump: halorhodopsin. This protein pumps negatively charged chloride atoms through the cell membrane, causing the light-driven absorption of salt.
Moreover, the scientists managed to systematically modify bacteriorhodopsin’s properties. Replacing individual amino acids produces molecules that are sensitive to light of different wavelengths or respond more slowly to light. These biotechnological variants of bacteriorhodopsin have the potential for a myriad of technical applications, which Dieter Oesterhelt, together with Norbert Hampp from the University of Marburg, has spent many years investigating. Variants of bacteriorhodopsin, which switch more slowly than the natural molecule between a form that is or is not exposed to light, can be used for optical data storage, for example.
Bacteriorhodopsin can now also be used as a photochromic pigment for optical security applications. The protein’s colour changes from purple to yellow when it is exposed to light. Documents created using printing inks containing bacteriorhodopsin are bleached after exposure to light - proof of their authenticity. At the same time, the bleaching of the printing ink also protects against copying, as the light that it is exposed to during copying or scanning causes the colour to change. A number of patents and a start-up company are proof that Dieter Oesterhelt realised, at an early stage, the potential applications of his discovery and participated in their technological implementation.