Fleming, along with Kris Niyogi, Nancy Holt, and others in the Fleming Lab, determined that when chlorophyll molecules in green plants take in more solar energy than they are able to immediately use, molecules of zeaxanthin, a member of the carotenoid family of pigment molecules, carry away the excess energy. The results are reported in the January 21, 2005 issue of the journal Science.

All plants regulate the harvesting of sunlight for photosynthesis by getting rid of excess absorbed light energy as heat. This regulatory mechanism is called nonphotochemical quenching or feedback de-excitation. Somehow, excited chlorophyll molecules are de-excited in a process that involves a specific carotenoid, zeaxanthin, that is made only in high light. This finding is significant because it shows, unexpectedly, that a zeaxanthin cation radical is the key molecular species involved in this process. details about the Fleming discovery -->

Graham Fleming awarded Porter Medal
Graham Fleming, director of the Physical Biosciences Division, was selected by the photochemical societies of Europe, Asia, and the Americas to receive the Porter Medal. The medal honors Fleming's life-long work in the field of photochemistry. It is presented every two years on the occasion of the International Union of Pure and Applied Chemistry (IUPAC) symposium. The 2004 medal was awarded to Fleming in July 2004 during a ceremony in Spain.