Ultraviolet radiation, evolution and the pi-electron system

Ultraviolet radiation is an important natural mutagen. Because of the energetic characteristics, the carbon compounds most susceptible to UV absorbance are those that contain pi-electron systems. The pi-electron configuration is most commonly represented in organic chemistry within aromatic ring structures. An analysis of a wide range of biochemically important processes shows that the susceptibility of this system lies at the heart of almost all UV radiation effects on life. Its disruption accounts for UV radiation-induced damage in nucleic acids, proteins and lipids. However, throughout the evolution of the biosphere, life has also used the UV absorbance of pi-electron containing compounds to screen out UV radiation, turning their UV absorbance into a protection mechanism. Although UV radiation effects can be analyzed in terms of organism physiology, a more reductionist analysis shows the pi-electron system to be the common chemical determinant in the evolution of UV radiation damage effects and protection strategies in organisms. It reveals an interesting evolutionary story. (C) 1998 The Linnean Society of London.