Photophysics and Spectroscopy of Fluorophores in the Green Fluorescent Protein Family

Abstract

Proteins homologous to the green fluorescent protein (GFPs) form a large family of unconventional, genetically encoded fluorophores with widely diverse colors and applications, which have profoundly renewed the fields of biological imaging and drug screening. Their detailed spectroscopy stems from a complex interplay between the electronic properties of a relatively simple, yet flexible and multiprotonable chromophore formed after specific biosynthesis, and the spatial and dynamic organization of its protein carrier. Early experimental and theoretical studies of GFP fromthe Aequorea victoria jellyfish and ofmodel synthetic compounds have revealed that chromophore twisting, cis-trans isomerization, proton transfer, and electron transfer are major excited state reactions that determine its photophysics and photochemistry. It has been found later that quite similarmechanisms are at work in several distant members of the GFP family, suggesting a unified picture that may guide the future development of new GFP-based biosensors.