Design and synthesis of pH sensitive GFP chromophore analogs

ORGN 688

Megumi Yoshioka-Tarver, and C. Dennis Hall, Department of Chemistry, University of Florida, Gainesville, FL 32611-7200
Fluorescent peptide labeling is a useful method for monitoring the biological activity of ligands, inhibitors, or antigens at low concentration. Green Fluorescent Protein (GFP) is the most popular fluorescent tagged protein widely used for monitoring biological activity. Several GFP modified compounds have been synthesized and studied for their fluorescent abilities, however, the synthesized GFP chromophore analogues only showed small fluorescence activity because of photoisomerization of the exo-methylene group. The object of our research was to design and synthesize new GFP chromophore analogues and to overcome the photoisomerization problem. The GFP chromophore analogues 1 and 2a-e have been synthesized. Photoisomerization and fluorescence sensitivity towards pH of these analogues were examined. The analogues act as molecular switches and fluoresce under acidic condition due to six-membered ring intramolecular hydrogen bonding.