Abstract
Aspects of intramolecular light energy and electron transfer are discussed for three protein cofactor complexes whose three‐dimensional structures have been elucidated by X‐ray crystallography: the light harvesting phycobilisomes of cyanobacteria, the reaction center of purple bacteria, and the blue multi‐copper oxidases. A wealth of functional data is available for these systems which allows specific correlations to be made between structure and function and general conclusions to be drawn about light energy and electron transfer in biological materials.